Table of Contents Program 2 Acknowledgements 4 What Have ... copy/sheep... · Yves Berger 63 Past Recipients of the Sheep Industry Award 66 Index 67 3. ... Madison (Michel Wattiaux,

Table of Contents

Program 2

Acknowledgements 4

Welcome 5Robert E. Rand

What Have We Learned About Artificial Insemination in Sheep?Randy Gottfredson 6

Feeding Ewes Better for Increased Production and ProfitDr. Dan Morrical 10

Rumen-Protected Bypass Fat for Dairy Ewe Commercial Milk ProductionBrett C. McKusick, Yves M. Berger and David L. Thomas 15

Progress Report: A Comparison of Market Lambs Sired by Suffolk Ramsof United Kingdom or U.S. Origin

David L. Thomas, Yves M. Berger, Brett C. McKusick,Randy G. Gottfredson and Rob Zelinsky 27

Effects of Three Weaning/Rearing Systems on Commercial Milk Productionand Lamb Growth

Brett C. McKusick, Yves M. Berger and David L. Thomas 33

Preliminary Results: Effects of Udder Morphology on Commercial MilkProduction of East Friesian Crossbred Ewes

Brett C. McKusick, Yves M. Berger, and David L. Thomas 49

Introgression of the FecB Allele of the Booroola Merino into a Rambouillet Flock - AProgress Report

A.E. Crooks, D.L. Thomas, R.D. Zelinsky, R.G. Gottfredson, B.C. McKusick 61

1998-99 Reproductive Performance of the Spooner Agricultural ResearchStation Flock

Yves Berger 63

Past Recipients of the Sheep Industry Award 66

Index 67

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ACKNOWLEDGMENT OF SUPPORT FOR SHEEP RESEARCH AND EXTENSIONPROGRAMS AT THE UNIVERSITY OF WISCONSIN-MADISON

Each year, a number of people and organizations support the sheep research and Extensionprograms of the Department of Animal Sciences, University of Wisconsin-Madison. Withoutsuch support, much of our sheep work would not be possible. The following organizations andpeople are thanked for their generosity in 1998-99.

Dave Thompson, Editor, Sheep! Magazine, for providing morning refreshments at the 1999Spooner Sheep Day.

Indianhead Sheep Breeders Association for assistance with planning and conducting the 1999Spooner Sheep Day (Larry and Emily Meisegeier and David Erb, Spooner Sheep Day Plan-ning Committee).

Babcock Institute for International Dairy Research and Development, University of Wisconsin-Madison (Michel Wattiaux, Director) for support of the 1999 Great Lakes Dairy SheepSymposium and dairy sheep research.

Wisconsin Sheep Breeders Cooperative (WSBC) for co-sponsoring the 1999 Beginning SheepShearing Schools (Larry Becker, President and Barb Bishop, Secretary-Treasurer). TheWSBC also serves a valuable educational and service function in their sponsorship of theWisconsin Sheep Industry Conference (Bob Black, Coordinator) and the Wisconsin CentralRam Test (Nils Nelson, Station Manager and Gary Vondrachek, Ram Test Committee Chair-man).

College of Agricultrual and Life Sciences, University of Wisconsin-Madison (Elton Aberle,Dean; Margaret Dentine, Associate Dean of Research; Dick Straub, Director of AgriculturalResearch Stations) for support of sheep research activities on campus and at the Arlingtonand Spooner Stations.

University of Wisconsin-Extension (Carl O’Connor, Dean of Cooperative Extension andEd Jesse, CALS Associate Dean of Extension) for support of sheep Extension programs.

Several people and organizations for valuable contributions toward the success of the U.K./U.S.Suffolk trial including donation of ram semen, collection of carcass data and consultations:U.K. Suffolk Sire Reference Scheme (David Hram, Secretary), National Suffolk SheepAssociation (David Kloostra, Executive Director), Edinburgh Genetics (Ian McDougall andJames Mylne), Elite Genetics (Dennis Gourley and Deb Gourley), Alan Culham, WolverinePacking (Dale Brooks), Culham and Stevens Suffolks, Bob Kim, Don Swanton, and TomBurke.

Thank you.

David L. ThomasProfessor, Sheep Genetics and Management

and Extension Sheep Specialist

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WELCOME

Robert E. RandSpooner Agricultural Research Station

University of Wisconsin- Madison

Welcome, ladies and gentlemen, to the 47th annual Spooner Sheep Day. I would intro-duce and welcome Dr. Richard Straub, Director of Ag Research Stations. Professor Straubreplaces Dale Schlough, who retired in June of 1999. Professor Straub is by training an engineer,just recently being chairman of the Department of U.W. Biological Systems Engineering. He isnot new to this area, as he did research work on forage drying rates at the Hayward ResearchStation.

The direction of crops research at the Spooner Ag Research Station is taking a differentdirection, due to the changing status of land use in the area. Dairy farm numbers have declineddramatically in the last 20 years . The problem now is what to do with vacant land. Some lands aresuitable for crop production, but much pasture land and other lands only marginally suitable forcrop production lie idle, to be overcome with weeds, unmarketable brush and trees, or worst of all,houses.

Short rotation intensive culture poplar trees (“ Fast Trees”) are being investigated as acrop for Northern Wisconsin landowners at the Spooner Ag Research Station. Why these trees?In Wisconsin, the supply of wood fiber doesn’t meet the demand, driving up raw material costs.These hybrid poplars require relatively low inputs of chemicals and fossil fuels. The hybridpoplars have a variety of possible end uses, including pulp (for paper), lumber, and millwork.

Hybrid poplars are clones. That means that they are vegetatively propagated. Segmentsof stems or branches, called cuttings, are collected from superior trees and used to produce newtrees. That is, a piece of stem with no roots or leaves is planted, sprouts, and grows into a newtree. Weed control is important the first three years after establishment; deer protection is a mustuntil the trees are higher than the deer browse line. Many poplar clones will grow more than 6feet per year. Some at the Arlington Research station have grown 11 feet in 6 months. Theeconomic rotation for hybrid poplar is 12-15 years. Forecasted yields are in the range of 3-5cords/acre/year. That means 36 to 75 cords/acre at harvest, or from 12.1 to 5.8 trees per cord.Many grant programs are available in Wisconsin for private landowners that either share costs ofestablishment or help with property taxes.

There are 5 acres of cuttings planted at the Spooner Ag Research Station. They can beobserved in a field located along the west side of Highway 53, just south of Ojibway road. Calleither the station at (715)-635-3735 or Jill Calebro at (608) 265-9832 for more information,concerning establishment costs, soil preparation,etc.

I am retiring from Ag Research Stations this coming January. I have enjoyed my part inSheep Day and my part in the sheep research at the Station. A lot of changes have taken place;many advances have been made. I believe the sheep industry has a bright future, especially inthe area of dairy sheep. Have a good day, and good luck in the sheep business.

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WHAT HAVE WE LEARNED ABOUT ARTIFICIAL INSEMINATION IN SHEEP?

Randy GottfredsonDepartment of Animal Sciences

University of Wisconsin-Madison

After years of experience with different methods of transcervical artificial insemination(TAI) in sheep, we have learned much. We know much more about the timing of estrus synchro-nization and the timing of insemination in the ewe. We have learned that just being able tocompletely pass through the cervix of a ewe and deposit semen directly into her uterus will notautomatically bring about pregnancy. We have also learned a lot about the endocrine system ofthe ewe. All of these things have helped advance the technology of transcervical AI. Summarizedbelow are two research studies conducted at the University of Wisconsin to compare two of themost promising methods of TAI against laparoscopic (surgical) artificial insemination (LAI).

A Comparison of Laparoscopic Intrauterine and Transcervical(Guelph System) Techniques of Artificial Insemination of Ewes. (1997)

A major objectives of this study was to evaluate the effects of theGuelph System forTranscervical Artificial Insemination, (GST-AI) and Laparoscopic Artificial Insemination (LAI)on the lambing rates, prolificacy, and gestation length for ewes.

Ninety-three ewes were artificially inseminated with frozen-thawed ram semen either byGST-AI or LAI once on December 9 or 10, 1997 at the Department of Animal Sciences, Univer-sity of Wisconsin-Madison. The ewes were randomly assigned to either GST-AI (47 head) orLAI (46 head).

On December 19, 1997, all ewes, in groups of 20, were exposed to one of six intact ramsfor natural service. On February 9, 1998, ewes were ultrasounded by an experienced technicianto determine pregnancy, gestational age, and number of feti. Pregnancy was determined by thepresence of fetal structures and cotyledons. The ultrasound unit also estimated gestional ageusing fetal body width measurements made by the technician. Ewes inseminated artificiallywould have been either 60 or 61 days pregnant; ewes that failed to conceive to artificial insemi-nation but conceived naturally would have been an average of 42 days pregnant.

Of the 93 ewes ultrasounded, 82 of them lambed (88.3%) to either AI or to natural ser-vice. Three ewes were predicted pregnant and did not lamb; all ewes predicted not pregnant didnot lamb. Actual gestational age for ewes lambing to AI was predicted 95% of the time within±7 days.

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Overall lambing rate to AI was 32.3% (30/93). Lambing rates to AI in this experiment arelower than previous intrauterine AI comparisons, however they confirm the relative superiorityof the LAI method. The decreased lambing rate might be explained by the fact that all eweswere bred without detection of estrus. Additionally, overall flock fertility is 88.4% (82/93) whichis lower than expected and also probably contributes to the decreased lambing rates to AI..Lambing rate for ewes inseminated on December 10 for both methods was 38.9% which furthersupports claims that GST-AI can be a suitable method for insemination of ewes with frozen-thawed semen however our results confirm its unfortunate inconsistancy.

The effects of LAI and GST-AI on future reproductive performance has been evaluated interms of histological trauma to the reproductive tract as well as in terms of subsequent fertilityto natural matings. Campbell et al. (1996) and McKelvey (1994) have shown that there is epithe-lial damage to the lining of the cervix ranging from bruising to puncture of the cervical wallwhen the GST-AI technique is used. The LAI technique, however, results in no fibrinous adhe-sions nor detectable damage to the reproductive tract when examined 3 to 5 days followinginsemination (McKelvey et al., 1985). It is possible that ewes not achieving conception to GST-AI could thus have decreased fertility to subsequent natural insemination due to local inflamma-tion and possibly cervical infection.

Insemination procedure times of 5.3 and 2 min for the GST-AI and LAI respectively areconsistant with that of other authors (Buckrell et al., 1994; Windsor et al., 1994). Factors thatinfluence the degree of cervical penetration with GST-AI and ultimately prolong inseminationprocedure time include: individual anatomical variation of the cervix, parity of the ewe, estrusstatus of the ewe, experience of the technician and adequate restraint of the ewe.

For further information about this study, please see:

McKusick , B.C., D.L. Thomas, R.G. Gottfredson, Y.M. Berger, and R.D. Zelinsky. 1998. AComparison of Transcervical and Laparoscopic Interuterine Artificial InseminationTechniques on Reproductive Performance of Ewes. 46th Annual Spooner Sheep DayProceedings. pp. 32-39 .

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A Comparison of the Laparoscopic Intrauterine and the Gourley Scope TranscervicalMethods of Artificial Insemination of Ewes. ( 1998)

Cooperators

R. Riese and D. D. Gourley (Elite Genetics, Waukon, IA).

Objective

Compare the reproductive performance of ewes that have been laparoscopically insemi-nated or transcervically inseminated by a fiber-optic scope apparatus (Gourley Scope™, Elite Vi-sions, Waukon, IA).

Procedure

Prior to the experiment, ewes were randomly assigned to be inseminated laparoscopically(LAI) or by the Gourley Scope™ (GAI), a small flexible fiber-optic scope apparatus that is passedthrough the cervix to deposit semen directly into the uterus. Ewes were inseminated on eitherDecember 3 or 4, 1998. LAI ewes were inseminated by one experienced technician and GAI eweswere inseminated by a different technician with experience using the Gourley ScopeTM. For theGAI method, an additional two ml of diluent was used to flush the semen out of the sheath andguarantee delivery of the entire dose into the ewe. The diluent used for flushing and thawing wasthe same diluent used to freeze semen for this experiment. Fertile rams were put with the ewes asa cleanup measure on December 14, 1998.

Ewes were ultrasounded by an experienced technician on February 8, 1999 (67 or 68 daysafter insemination), and fetal age was estimated by fetal body width measurements. Ewes withpredicted gestational age of 62 days or greater were considered to have conceived to artificialinsemination. At the time that this report was prepared, ewes had not yet lambed. Lambing datalater fully supported the conception rates indicated by ultrasound examination as mentioned below.

Results

Conception rates to artificial insemination were low for both methods: none of the GAI ewes,and only 46% of the LAI ewes, were predicted to be pregnant (Table 1). Sperm concentration used forinsemination in the present experiment was high and may have been detrimental to conception for bothmethods. Also, repeated exposure to PMSG is known to lower conception rates. Conception rates toLAI were higher (P < .05) on December 3 than on December 4 (data not shown) and may have been dueto a difference in semen quality between the two days. Four- and five-year-old ewes had the highest (P< .05) predicted conception rate, two- and three-year-old ewes were intermediate, and none of the six-year-old and greater ewes were predicted to be pregnant. The older ewes may have relatively lowfertility and conception rates because of their age or quite possibly because of prior multiple laparoscopicexaminations and inseminations. The previous year’s artificial insemination method (Guelph System oftranscervical insemination, by laparoscope, or no artificial insemination) did not significantly affectconception rate.

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Insemination procedure time for the GAI method was nearly twice (P < .05) that of the LAImethod. Procedure time was shortened (P < .05) when ewes were bred closer to the onset of heatrather than later.

For further information about this study, please see:

Crooks, A.E., B.C. McKusick, R.G. Gottfredson, R.D. Zelinsky, D.L. Thomas. 1999.Comparison of two artificial insemination methods in Rambouillet ewes. Proceedings of the1999 NCR-190 Technical Committee. pp. 21-23.

Results for artificial insemination procedure time, and conception rates predicted by ultrasonography at 68 d post-insemination

Factor Number of ewes Procedure time, Conception toinseminated min A.I., %

1997 A.I. methodTranscervical (Guelph Sys.) 47 5.30a 20.7a (10/47)

Laparoscopic 46 2.14b 43.9b (20/46)

1998 AI methodGourley Scope® 39 4.54a 0a (0/39)

Laparoscopic 36 2.33b 45.6b (17/36)

DayDecember 3 38 3.49 28.9December 4 37 3.39 17.1

Ewe age2 to 3 yr 38 3.21 25.9a

4 to 5 yr 22 3.43 44.3b

≥6 yr 15 3.67 0c

a,b,c Within a column and of an independent factor, means lacking a common superscript letter are different (P < .05).

Intrauterine artificial insemination of frozen-thawed ovine semen in the United States providesa valuable alternative to natural mating for more effiecient genetic improvement of sheep breeds.Laparoscopic insemination remains superior to transcervical insemination for acceptable pregnancyrates and the inferiority of the latter is due largely to its inconsistency. From our experience it appearsthat no transcervical method of artificial insemination has shown the consistent pregnancy rates as seenin our laparoscopic inseminations. Our enthusiasm and work of searching for effective methods oftranscervical insemination in sheep is far from over. There are several ideas out there that we are excitedabout. It will time and experience to determine whether or not they will be able to replace laparoscopicAI.

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FEEDING EWES BETTER FOR INCREASED PRODUCTION

AND PROFIT

Dr. Dan MorricalDepartment of Animal Science

Iowa State University, Ames, Iowa

Introduction

Sheep nutrition and feeding is extremely critical to the success or failure of the ewe flock enter-prise. As shepherds our task is to provide balanced rations to the ewes that meets their nutrient require-ments on the least costly basis. Feed costs account for half the cost of producing lamb and wool.Therefore, cost control must always be foremost in the shepherd’s mind. Sheep enterprises face agreater challenge in meeting needs of the flock because of the large within flock and between flockvariation. This factor is best demonstrated by the requirements of ewes nursing singles, twins or tripletslisted in table 1. This paper reflects the general guidelines for feeding ewes; however, each operationmust adapt and modify these guidelines for their specific operation.

Nutrient Requirements

The amount of nutrients the sheep require is affected by several factors. These include eweage and weight along with stage of production and level of production. Figure 1 outlines the stages ofproduction, demonstrates how nutrient requirements change through the production cycle. It isimportant to realize that all ewes in the flock are not at the same stage of production on any given day.This factor is affected by the length of the breeding season and production system (once a year lamb-ing versus accelerated lambing systems).

Critical phases of the production cycle include flushing/breeding as it sets the maximum droprate for flock. Early/mid gestation is critical in that placental development occurs from day 30-90 ofgestation. Placental size or weight effects nutrient transfer between the ewe and fetuses. Underdevel-oped placenta results in smaller birth weights regardless of late gestation nutrition. Twenty days ofsevere underfeeding or 80 days of slight underfeeding will both retard placental growth. The remain-der of this paper will deal with late gestation and lactation stages of production since in most flocksewes are grazing during other production phases.

Late Gestation Nutrition

Determining how much to feed ewes in late gestation is a very difficult practice. Recentdevelopment with ultrasound scanning for fetal number allows for fine tuning the late gestationnutrition. The goal of late gestation nutrition program is to insure adequate nutrient intake for strongvigorous lambs of moderate birth weight. Additionally, ewes must enter lambing season in average toabove average body condition to maximize milk production. Birth weight of lambs is critical to asuccessful lambing season. Small lambs have less resistance to cold stress and reduced pre-weaninggrowth. Big lambs increase the incidence of lambing problems and increases shepherd labor andlamb death loss. Fetal scanning and the separation of ewes into different feeding groups by thosecarrying singles, versus twins versus triplets or more helps to reduce the real big singles or small twinsand triplets. Experienced technicians have accuracy’s above 90% on fetal numbers so contracting anexperienced scanner is the key to successful implementation of this technology.

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The nutrients of greatest concern during late gestation feeding would be energy (TDN), crudeprotein (CP), calcium, selenium and vitamin E. The TDN level required is affected by the number offetuses and cold stress. Winter lambing ewes generally cannot consume enough forage alone to meettheir energy requirements. Thus, requiring the feeding of concentrates (corn).

Fetal growth accelerates rapidly during late gestation. Furthermore, energy required is muchhigher for the two weeks prelambing versus six weeks prelambing. A means of controlling costs is tostep up grain feeding as lambing approaches. Ewes carrying singles require less grain and do notneed to receive grain as early as those carrying multiples. Late gestation rations should begin 5-6weeks prelambing for ewes carrying triplets and their ewes. Those with twins can be delayed to 3-4weeks prelambing whereas those with singles can be held off until two weeks prelambing.

The absolute level of grain to feed is highly dependent upon the nutrient density of the foragebeing fed. Table 2 demonstrates the huge variation in nutrient density of hays. Nutrient analysis costs$10-$20 per sample and is money well spent. Balancing diets based on average or book values forhays is a risk progressive shepherds should not take especially in highly productive flocks. Further-more, one can not accurately determine the nutrient density of hays with visual appraisal. Table 3provides example rations for all phases of production with a wide array of forage sources. To mini-mize the risk of acidosis from excess grain feeding, ewes receiving over 1.5 pounds of concentrate perday should receive it in split feedings. Additionally, if hay does not need supplemented with proteinor minerals than whole corn should be fed.

Selenium and vitamin E are both critical micro-nutrients for lamb survival and a smoothlambing season. Selenium can be added to the ration of sheep at .3 PPM or .3 mg/kg of feed. Themaximum allowable selenium intake from supplemental sources can not exceed .69 mg per head perday. This is a very small amount and extreme care is required in calculating how much to add. Moreimportantly selenium at 2 PPM can be toxic. Selenium status of ewes is dependent upon both theselenium concentration and intake of the mineral, along with the selenium level in the feedstuffs.Flocks with a history of selenium problems in newborn lambs should consider force-feeding seleniumvia the grain mix. This insures all ewes consume adequate amounts on a more uniform basis. Ifselenium is force fed, there should not be a free choice mineral source available. Table 4 shows thelevel of intake required for various selenium concentrations in the mineral or trace mineral salt.Selenium crosses the placenta so newborn lambs selenium status is totally dependent upon the sele-nium of their dams in late gestation.

Vitamin E, unlike selenium is not toxic. Vitamin E also does not cross the placenta so anewborns only source of E is ewe’s milk or injections. The concentration of Vitamin E in ewe’s milkor colostrum is directly correlated with the Vitamin E intake of the ewe. Vitamin E levels are ex-tremely variable in feedstuffs because it denatures with storage and is also denatured in rumen asgrain feeding increases. Although NRC states 50 international units of Vitamin E intake is adequate,multiple studies have shown improved lamb performance and livability too much higher E feedinglevels. Unfortunately, high E supplementation does not show uniform, consistent results. Researchershave postulated this is related to the environmental stress during lambing. This creates a dilemma inthat one must predict weather conditions to determine if additional E would be beneficial. Vitamin Eis very cheap and therefore feeding 100 iu per fetus or lamb nursed per ewe per day is a preventativestep that is money wisely invested.

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Lactation nutrition mistakes

One of the most common mistakes inexperience shepherds make is over feeding grain to theewes in the lambing jug. This situation most frequently occurs when we try to accelerate the milkoutput in ewes that do not have enough to feed their lambs. This over feeding can create problemswith acidosis and lead to less milk production rather than more. Newborn lambs probably do notconsume more than 10% of their bodyweight in the first day or two of life, so it is not critical thatewes be pushed in while in the jug.

Nutrition Disorders During Late Gestation

Ketosis or twin lamb disease is the most often discussed nutritional disorder that occurs duringlate gestation. In the Midwest, corn is really cheap and ketosis should never happen. The cause ofketosis is inadequate energy intake by the ewe resulting in fat metabolism (fat breakdown to feed therapidly growing fetuses). Ewes which are most prone to ketosis would be those that are timid eatersor smaller ewes that do not consume their fare share of grain. Overly fat ewes also tend to be moresusceptible to ketosis. I believe this is due to reduced intake capacity from internal fat and increasedfat resources for breakdown. Granny ewes or ewes with poor mouths are also likely candidates forketosis. Prevention is best accomplished by monitoring condition scores and keeping ewes frombecoming obese. Thin ewes can be sorted off and fed separately so that they can be fed better andinsuring that they are consuming their fare share. It is important that thin ewes are sorted out earlyenough to allow sufficient time (60d) for getting them to the correct condition score by lambing.

Vaginal prolapses Protein and energy are both critical nutrients for milk production. If eithernutrient is fed below the requirement, milk yields and subsequently lamb gains will be reduced 10%or more depending upon the magnitude of the short fall.

I would suggest that almost all ewes lose weight during lactation, many over 35 pounds. Thisoccurs because energy intake is well below requirements and ewes must mobilize body stores tosustain milk production. Weight loss during lactation is the critical reason that late gestation nutritionbe adequate to insure ewes are in average or better body condition at lambing. Traditionally, fatmobilization during lactation was considered as a means of controlling feed costs. However, excessweight loss is not without its costs. Ewes losing less than .5 condition score during a 60-day lactationwill not suffer in terms of milk yield. Since one condition score equates to an 11% change in bodyweight, a 200 pound ewe could only lose 11 pounds (200 x 5.5%). This value would equate too lessthan .2 pounds of weight loss per day. It would not be uncommon for many ewes to lose two to threetimes this amount.

Weight loss during lactation impacts protein requirements. The more weight ewes lose thehigher their protein need. This situation is due to the ewe’s ability to effectively mobilize body fat buthaving minimal ability to mobilize body protein for milk synthesis. With the current low cost ofgrain, it is economically wiser to feed more corn to limit weight loss versus feeding extra protein tobalance energy from fat breakdown. It is also important to realize that fat conversion to milk is about60% under protein and energy deficient rations whereas with adequate protein fed, fat conversion tomilk is 80%. To demonstrate this relationship between protein requirements and weight loss, a ewelosing .5 pounds per day requires a lactation ration containing 21% crude protein. However, if theenergy intake is increased to prevent weight loss, this ewe would require only 11.5% crude protein intheir ration.

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The next mistake that needs to be avoided is over feeding the ewes in the week to ten daysbefore weaning. Many flocks routinely wean ewes while in the peak stage of milk production. It iscritical that shepherds modify the pre-weaning diet of ewes to reduce mastitis problems. This is easilyaccomplished by cutting off the grain feeding for the last 10 days before weaning along with feedinglow quality hay. This management input is trying to limit the ewe’s protein and energy intake as bothnutrients are required for milk production. Feeding straw for the last 2-3 days before weaning isfurther shuts down milk production. After weaning ewes should be maintained on low quality feedfor 3-7 days to assist ewes in drying up. If ewes are fed by number nursed, it is important to moveewes to the next lower ration if they lose a lamb or lambs.

Summary

A wise county extension director told me once that when it comes to feeding livestock “onecan not feed profit nor can one starve a profit”. The important factors for profitable sheep productionare controlling feed costs and increasing output. Either is pretty easy to do by itself doing both at thesame time takes effort and planning.

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14

RUMEN-PROTECTED BYPASS FAT FOR DAIRY EWE COMMERCIALMILK PRODUCTION

Brett C. McKusick, Yves M. Berger, and David L. ThomasDepartment of Animal Sciences and Spooner Agricultural Research Station


Summary

The effects of fat supplementation and weaning system on commercial milk yield andmilk composition were determined on 129 East Friesian crossbred ewes. Prior to lambing, eweswere randomly assigned to one of two weaning systems. The DY1 system involved weaning ofewes from their lambs within 24 to 36 hr post-partum and then twice-daily machine milking. Inthe MIX system, ewes had access to their lambs during the day, were separated from their lambsovernight, and were machine milked once daily in the morning. After approximately 30 days inlactation, lambs were weaned from the MIX system ewes, and all ewes were machine milkedtwice daily. Additionally, calcium salts of fatty acids (CSFA) were premixed in a concentrateration and fed to all ewes (100 grams/ewe/day) for 2 two-week periods during early lactation.Each CSFA feeding period was separated by two weeks of not feeding CSFA. Milk yield wasmeasured weekly, and milk samples were analyzed for percentage of milk fat and protein andsomatic cell count. During the first 30 days of lactation, DY1 ewes produced 38% more com-mercial milk, 73% more kilograms of fat, 42% more kilograms of protein, had significantlyhigher percentages of milk fat (5.90 vs 2.51%, respectively), and similar percentages of milkprotein compared to MIX ewes. Following weaning, commercial milk, fat, and protein yieldsfrom MIX ewes were significantly more than those of DY1 ewes. CSFA supplementation didnot influence commercial milk yield. Percentage and yield of milk fat was significantly higherfor DY1 ewes that received CSFA supplementation compared to unsupplemented DY1 ewes.Conversely, for the MIX system, percentage and yield of milk fat was unchanged betweenCSFA-supplemented and unsupplemented ewes prior to complete weaning at 30 days post-partum. For both the DY1 and MIX systems, percentage and yield of milk protein tended to besuppressed in CSFA-supplemented vs unsupplemented ewes. Somatic cell count was not signifi-cantly affected by either weaning system or CSFA supplementation. As previously confirmed inthis flock, weaning system significantly influences commercial milk production and compositionduring the first 30 days of lactation. CSFA supplementation did not increase percentage noryield of milk fat in partially suckled ewes. CSFA supplementation of dairy ewes in early lactationinduces a slight suppression in milk protein and increases milk fat yield provided that ewes havebeen completely weaned from their lambs. According to a proposed milk purchase price sched-ule from one sheep-milk processing facility where payments are based on milk fat percentageand other indicators of milk quality, CSFA-supplemented milk appears to offer greater financialreturns compared to unsupplemented milk.

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Introduction

Percentage of milk fat for East Friesian crossbred ewes at the Spooner AgriculturalResearch Station has been low in previous years (Thomas et al., 1999; McKusick et al., 1999).Additionally, when a mixed weaning system (partial suckling and once daily machine milking) isused for the first 30 days of lactation, percentage of commercial milk fat is suppressed, quitepossibly due to retention of fat in the udder for as long as the ewe is in partial contact with herlambs (McKusick et al., 1999). Also, milk yield is inversely proportional to percentage of milkfat, and therefore in high-producing dairy-ewe breeds such as the East Friesian, reported averagepercentages of milk fat are low compared to other non-dairy or low producing dairy breeds(Casoli et al., 1989). However, owing to large commercial milk yields of dairy breeds, fat yieldis ultimately superior to that of domestic breeds. Nonetheless, milk processing facilities aredestined to favor milk with a higher percentage of milk fat and thus, milk produced with a lowpercentage of milk fat may potentially be at a serious economic disadvantage. In dairy ewes,protected fat supplementation has been shown to result in either similar (Hernandez et al., 1986;Casals et al., 1992; Caja and Bocquier, 1998) or increased (Sklan, 1992) commercial milk yieldrelative to controls; all authors report increases in both percentage and yield of milk fat. There-fore, it is hypothesized that feeding rumen-protected bypass fat to dairy ewes might increaseoverall fat percentage, fat yield, and furthermore, possibly reduce the negative effects of partialweaning systems on milk fat content. The objective of this experiment was to determine theeffects of calcium salts of long-chain fatty acids (CSFA) supplementation on dairy ewe milkproduction and to evaluate concurrent effects with two weaning systems.

Materials and Methods

Megalac® Rumen Bypass Fat (Church and Dwight Co., Inc.) was pre-mixed in a concen-trate ration of corn and a protein pellet (diet crude protein of 16%) to provide 100 grams CSFAper ewe per day. CSFA was fed twice daily to second, third, and fourth parity East Friesiancrossbred ewes for 2 two-week periods beginning March 3, 1999, which were proceeded andseparated by two weeks of no supplementation (Table 1). Throughout the experiment, all ewesreceived legume-grass hay (crude protein of 20%). During the two weeks of feeding CSFA, allewes received the supplement. Likewise during the two weeks of not feeding CSFA, no ewesreceived the supplement. Ewes gave birth over a six-week period beginning February 10. Thusduring all stages of lactation, ewes were receiving or not receiving CSFA in their diet, which wasrandomly determined by their lambing date.

Additionally, prior to lambing, ewes were assigned to one of two weaning system treat-ments. DY1 ewes were weaned from their lambs between 24 and 36 hr post-partum, and thenmachine milked twice daily for the remainder of lactation. MIX ewes, beginning 24 hr post-partum, were separated from their lambs at 1700 each day and milked once daily every morningat 0600. After the morning milking, ewes were returned to their lambs. MIX ewes were milkedtwice daily following permanent weaning of their lambs at approximately 28 days of age.

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Machine milking of ewes took place in a 12 x 2 milking parlor with indexing stanchionsand a high-line pipeline system (Alfa Laval-Agri, Tomba, Sweden). Milking machine settingsincluded a pulsation rate of 180/min, a ratio of 50:50, and a vacuum level of 38 kPa. Milkproduction was recorded weekly using a Waikato milk meter jar. Individual milk production wasrecorded on Tuesday evening and Wednesday morning, and samples for composition analysiswere taken on Wednesday morning. Milk composition analysis for percentage of fat, percentageof protein, and Fossomatic® somatic cell count was performed by a State of Wisconsin certifiedlaboratory. Milk production for each stage of lactation was calculated based on the weeklytestings. Somatic cell counts were transformed to base-10 logarithms. Least squares meansanalysis of variance was conducted with the GLM procedure of SAS (SAS, 1999). In addition tothe main treatment effects of CSFA supplementation and weaning system, other sources ofvariation included in the model were, parity (second, third, or fourth), litter size (one, two, orthree-and-greater), and all two-way interactions. This report presents results obtained from thefirst 42 days of the 1999 lactation.

Results and Discussion

Milk composition of the weekly bulk-tank samplings is presented in Table 1. Corre-sponding to the presence or absence of CSFA supplementation, percentage of milk fat tended tobe higher when CSFA was being fed, and low when CSFA was not fed. Percentage of milkprotein and somatic cell count (SCC) did not seem to demonstrate this relationship, howeverpercentage of milk protein did tend to decline with time.

CSFA supplementation tended not to affect commercial milk production for either theDY1 or MIX weaning systems (Table 2), which is consistent with other authors (Hernandez etal., 1986; Casals et al., 1992; Caja and Bocquier, 1998). As previously reported in this flock(McKusick et al., 1999), weaning system was a significant source of variation in commercialmilk yield (Table 2). DY1 ewes produced 26% more (P < .01) commercial milk than MIX ewesduring the first 42 days of lactation (94 and 84 L/ewe, respectively). This is to be expected asMIX ewes were being milked only once per day for at least the first 30 days, and in addition,MIX ewes were raising lambs. DY1 ewes had superior (P < .0001) commercial milk yieldrelative to MIX ewes for the first 28 d of lactation, after which MIX ewes were equal or superior(P < .05) in milk production to DY1 ewes. These results imply that MIX ewes’ udders havehigher overall milk secretory capacity than DY1 ewes, at least during early lactation. For com-mercial milk production, there were no significant interactions at any stage of lactation betweenCSFA and weaning system treatments.

The interaction between CSFA and weaning system treatments was significant for moststages of lactation with respect to milk fat (Tables 3 and 5). For the first 30 days of lactation,MIX ewes had markedly suppressed (P < .0001) milk fat content compared to DY1 ewes whichconfirms previous reports for this flock of ewes (McKusick et al., 1999). Within the DY1 ewes,CSFA supplementation resulted in higher (P < .001) percentage of milk fat and kilograms of milk

17

fat at every stage of lactation compared to no supplementation (Table 3) which is in agreementwith other authors (Hernandez et al., 1986; Casals et al., 1992). Conversely, within the MIXewes, CSFA supplementation generally had no effect on percentage of milk fat nor kilograms ofmilk fat while the ewes remained in partial daily contact with their lambs. Despite exogenous fatsupplementation, poor milk ejection during the first 30 days of lactation perhaps is continuing toinhibit the adequate release of milk fat during machine milking (Muir et al., 1993; Marnet et al.,1999). During the d 36 to 42 stage of lactation, MIX ewes that were supplemented with CSFAfinally show an increase (P < .01) in percentage of milk fat compared to those not supplemented(Table 3). This perhaps indicates the gradual habituation of MIX ewes to having their lambsweaned and to machine milking and thus, more complete milk ejection and less retention of milkfat. Kilograms of milk fat produced by CSFA supplemented and non-supplemented MIX eweswere similar following weaning (Table 5), however it would be expected that as lactation pro-gressed, milk fat yield would be significantly higher in the CSFA-supplemented MIX ewes.

Percentage of milk protein was almost always lower (occasionally significant) for ewessupplemented with CSFA compared to unsupplemented ewes (Tables 4 and 6). CSFA supple-mentation of dairy ewes has been previously shown to either have no effect (Horton et al., 1992;Espinoza et al., 1998), or to suppress percentage of milk protein (Casals et al., 1992; Sklan,1992; Rotunno et al., 1998) probably due to decreased utilization of amino acids by the mam-mary gland (Cant et al., 1993). For the majority of the first 35 days of lactation, DY1 ewesproduced commercial milk that was higher (P < .01) in protein content than MIX ewes. Duringthe d 36 to 42 stage of lactation, which coincided with complete weaning of the MIX ewes, therewere no longer any significant differences between weaning systems. This reconfirms the aboveobservation concerning poor milk ejection during machine milking for the MIX ewes whilesuckling their lambs. The interaction between weaning system and CSFA treatments was notsignificant with respect to kilograms of milk protein, and tended to not be significant for percent-age of milk protein.

The ratio of milk fat to protein percentage should be greater than 1.0 (higher fat thanprotein) for desirable cheese manufacturing. Of the bulk tank samples taken during this trial(Table 1), all four taken during CSFA supplementation had fat:protein ratios greater than 1.0(range = 1.14 to 1.25), however, of the four taken during the nonsupplemented periods, only onesample had a ratio greater than 1.0 (range = .80 to 1.04). Furthermore, other authors haveshown a significant increase in palmitic (16:0) and linoleic (18:1) fatty acids, and significantdecreases in linoleic acid (18:2) and short chain fatty acids (C6 to C12) in milk from CSFAsupplemented ewes (Sklan, 1992; Appeddu et al., 1996; Caja and Bocquier, 1998) that will meritfurther organoleptic and compositional evaluation of cheeses made from CSFA supplementedewe milk.

Somatic cell count tended not to be significantly affected by either CSFA supplementa-tion or weaning system treatments (Table 7) and there were no significant interactions betweenthe treatments.

18

Implications

One of the major disadvantages of the MIX weaning system for dairy ewes is the mark-edly lower percentage and yield of milk fat while ewes remain in partial daily contact with theirlambs during the first 30 days of lactation (McKusick et al., 1999). CSFA supplementation failedto increase milk fat content during this period which implies that milk fat synthesis is probablynot impaired, but rather, milk fat is retained within the udder until its removal at the time of lambsuckling.

However, in the DY1 weaning system, milk fat content increased on average by 1.19percentage units for CSFA-supplemented versus unsupplemented ewes (Table 3). Sheep milkprocessing facilities have already begun to implement milk purchase agreements with producersthat are based on milk composition (percentage of fat) and quality (somatic cell count and bacte-rial plate count). One milk processing plant is considering a purchase agreement for sheep milkthat would pay a base price of $.45/lb of milk between 5 and 6.5% milk fat, $.48/lb between 6.5and 7% milk fat, and $.50/lb between 7 and 7.5% milk fat. Additionally, they have proposed apremium of $.0075 for each increase in .1% milk fat above 6%, provided that the milk has asomatic cell count below 400,000 cells/ml and a bacterial plate count below 40,000 plc. Withinthe present flock of ewes, milk from ewes not receiving the CSFA supplement would be worthonly $.45/lb. Milk from the CSFA-supplemented ewes would be worth between $.46 and $.60/lb, depending on the number of days in lactation. On average, each ewe in the DY1 systemproduced 5.10 lb (2.25 L) of commercial milk per day. CSFA supplementation costs approxi-mately $.10 per ewe per day, and therefore milk purchase price would have to average $.47/lbduring the period when CSFA is being supplemented in order to cover the increased costs of theCSFA supplementation. Given the above purchase agreement, returns generated per ewe by milksales from the DY1 CSFA-supplemented and non-supplemented ewes for the first 42 d of lacta-tion were $104.82 and $95.46, respectively. The difference in returns is $9.36, in favor of theCSFA-supplemented milk, which is more than twice the break-even difference of $4.20.

In conclusion, with respect to a day-one weaning system for dairy ewes, CSFA supple-mentation increases milk fat percentage and yield, and generates an additional $5.16 per ewe(above expenses) for the first 42 d of lactation, according to one proposed milk-purchasingagreement which severely discounts milk of low fat content. Other purchase price schemes,which do not severely penalize milk for low fat content, may allow for even more increases infinancial returns for CSFA-supplemented milk relative to non-supplemented milk. Further workis needed to evaluate the effects of CSFA supplementation on milk composition during mid tolate lactation, as well as the effects of CSFA on milk processing characteristics.

Acknowledgments

The authors wish to thank Dick Schlapper, Lori Brekenridge, and Ann Stellrecht. With-out their invaluable assistance in the intensive management and data collection required by theexperiment, this project would not have been possible.

19

Table 1. Milk composition of bulk-tank samples obtained during the CSFA supplementation trialMilk Composition

Sampling Number of CSFA† Milk fat, Milk protein, Somatic cell count,date ewes % % 1 x 103 cells/ml

2/17/99 27 no 4.39 5.10 300

2/24/99 39 no 5.70 5.48 400

3/3/99 51 yes 5.88 5.17 97

3/10/99 84 yes 6.52 5.25 600

3/17/99 116 no 5.06 5.25 700

3/24/99 123 no 4.20 5.20 420

3/31/99 135 yes 6.26 4.98 490

4/7/99 139 yes 5.98 4.84 230

†Calcium salts of long chain fatty acids (Megalac® Rumen Bypass Fat): 100 mg/ewe per day.

20

Table 2. Least squares means (±SE) for commercial milk yield (L/ewe) of the Weaning System and CSFA treatmentgroups

Weaning SystemNumber of

Stage of lactation ewes CSFA DY1 MIX

Day 1 to 7 63 no 16.3±.85a 9.72±1.1b

40 yes 15.6±.98a 8.06±1.4b

Day 8 to 14 76 no 18.8±.85a 10.6±1.3b

53 yes 19.7±1.3a 11.0±1.6b

Day 15 to 21 48 no 12.8±.65a 7.95±1.1c

70 yes 14.7±.64b 9.17±.87c

Day 22 to 28 34 no 16.3±1.1a 12.4±1.5b

76 yes 15.1±.71a 10.8±1.1b

Day 29 to 35 37 no 15.6±1.3b 19.9±1.7a

48 yes 12.8±.86c 14.3±1.5bc

Day 36 to 42 28 no 13.1±1.7a 20.8±4.1b

34 yes 14.5±1.7a 20.1±2.5b

Day 1 to 42 62 N/A 94.4±5.2a 84.0±12b

a,b,c Within a stage of lactation, means lacking a common superscript letter are different (P < .05).

Commercial Milk Yield

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 30 35 40

days post-partum

yiel

d, L

/day

DY1yes

DY1no

MIXyes

MIXno

21

Milk Fat Percentage

0

1

2

3

4

5

6

7

8

0 5 10 15 20 25 30 35 40

days post-partum

milk

fat

(%)

DY1yes

DY1no

MIXyes

MIXno

Table 3. Least squares means (±SE) for percentage of milk fat of the Weaning System × CSFA treatment combina-tion



Day 1 to 7 63 no 5.88±.25a 3.25±.34c

40 yes 7.30±.29b 3.68±.41c

Day 8 to 14 76 no 5.18±.15a 2.44±.23c

53 yes 6.50±.18b 2.38±.26c

Day 15 to 21 48 no 5.10±.16a 1.60±.26c

70 yes 6.13±.16b 2.12±.21d

Day 22 to 28 34 no 4.96±.27a 2.28±.38c

76 yes 6.15±.18b 2.31±.28c

Day 29 to 35 37 no 5.50±.39a 5.31±.52a

48 yes 6.50±.26b 4.21±.45c

Day 36 to 42 28 no 5.24±.22ab 4.49±.52a

34 yes 6.39±.21c 5.66±.32bc

a,b,c,d Within a stage of lactation, means lacking a common superscript letter are different (P < .05).

22

Milk Protein Percentage

3

3.5

4

4.5

5

5.5

6

0 5 10 15 20 25 30 35 40

days post-partum

milk

pro

tein

, %

DY1yes

DY1no

MIXyes

MIXno

Table 4. Least squares means (±SE) for percentage of milk protein of the Weaning System and CSFA treatments



Day 1 to 7 63 no 5.78±.09 5.75±.1240 yes 5.81±.11 5.64±.15

Day 8 to 14 76 no 5.40±.07a 5.33±.10a

53 yes 5.51±.08a 5.11±.11b

Day 15 to 21 48 no 5.45±.08a 5.13±.13b

70 yes 5.17±.08b 4.82±.10c

Day 22 to 28 34 no 5.44±.09a 4.85±.13bc

76 yes 5.02±.06b 4.81±.10c

Day 29 to 35 37 no 5.10±.12a 4.82±.16ab

48 yes 5.09±.08a 4.72±.14b

Day 36 to 42 28 no 5.28±.11 5.42±.2834 yes 4.98±.11 4.99±.17


23

Table 5. Least squares means (±SE) for kilograms of milk fat of the Weaning System and CSFA treatments



Day 1 to 7 63 no 1.00±.07a .36±.08c

40 yes 1.19±.08b .27±.11c

Day 8 to 14 76 no 1.02±.05a .27±.07c

53 yes 1.33±.07b .26±.09c

Day 15 to 21 48 no .68±.04a .14±.06c

70 yes .93±.04b .23±.05c

Day 22 to 28 34 no .82±.07a .35±.09c

76 yes .98±.04b .27±.07c

Day 29 to 35 37 no .86±.09ab 1.03±.12a

48 yes .85±.06ab .66±.10b

Day 36 to 42 28 no .71±.10a 1.00±.24b

34 yes .97±.10b 1.14±.15b


Table 6. Least squares means (±SE) for kilograms of milk protein of the Weaning System and CSFA treatments



Day 1 to 7 63 no .97±.05a .58±.06b

40 yes .95±.06a .47±.08b

Day 8 to 14 76 no 1.05±.04a .59±.06b

53 yes 1.12±.07a .57±.08b

Day 15 to 21 48 no .72±.03a .43±.05b

70 yes .79±.03a .46±.04b

Day 22 to 28 34 no .91±.05a .61±.07c

76 yes .79±.03b .54±.05c

Day 29 to 35 37 no .82±.06b 1.00±.09a

48 yes .67±.04c .70±.07bc

Day 36 to 42 28 no .71±.08a 1.15±.19b

34 yes .73±.08a 1.02±.12b


24

Somatic Cell Count

3

3.5

4

4.5

5

5.5

0 5 10 15 20 25 30 35 40

days post-partum

log

un

its

DY1yes

DY1no

MIXyes

MIXno

Table 7. Least squares means (±SE) for log-transformed somatic cell count (cells/ml) of the Weaning System andCSFA treatments



Day 1 to 7 63 no 5.04±.14 4.76±.1840 yes 5.14±.16 5.20±.23

Day 8 to 14 76 no 4.80±.10 4.78±.1553 yes 4.76±.12 4.55±.18

Day 15 to 21 48 no 5.02±.12a 4.45±.19b

70 yes 4.77±.12ab 4.52±.16b

Day 22 to 28 34 no 4.76±.14ab 4.46±.20b

76 yes 4.85±.09a 4.52±.15b

Day 29 to 35 37 no 4.98±.19 5.19±.2648 yes 5.03±.13 4.74±.22

Day 36 to 42 28 no 4.97±.18 4.92±.4434 yes 4.74±.18 4.85±.27

a,b Within a stage of lactation, means lacking a common superscript letter are different (P < .05).

25

Literature Cited

Appeddu, L. A., D. G. Ely, D. K. Aaron, W. P. Deweese, and E. Fink. 1996. Composition ofmilk fat from ewes fed a diet supplemented with calcium salts of palm oil fatty acids. Sheepand Goat Res. J. 12(1):11-18.

Caja, G. and F. Bocquier. 1998. Effects of nutrition on ewe’s milk quality. Cooperative FAO-CIHEAM Network on Sheep and Goats, Nutrition Subnetwork, Grignon, France, 3-5 Sep-tember.1-16.

Cant, G. P., E. J. Depeters, and R. L. Baldwin. 1993. Mammary amino acid utilization in dairyewes fed fat and its relationship to milk fat depression. J. Dairy Sci. 76:762-774.

Casals, R., G. Caja, X. Such, C. Torre, and X. Fàbregas. 1992. Lactational evaluation of effectsof calcium soap and undegraded intake protein on dairy ewes. J. Dairy Sci. 75(Suppl.1):174.

Casoli, C., E. Duranti, L. Morbidini, F. Panella, and V. Vizioli. 1989. Quantitative and composi-tional variations of Massese sheep milk by parity and stage of lactation. Sm. Rum. Res.2:47-62.

Espinoza, J. L., O. López-Molina, J. A. Ramírez-Godínez, J. Jiménez, and A. Flores. 1998. Milkcomposition, postpartum reproductive activity and growth of lambs in Pelibuey ewes fedcalcium soaps of long chain fatty acids. Sm. Rum. Res. 27:119-124.

Hernandez, M. P., J. J. Robinson, R. P. Aitken, and C. Fraser. 1986. The effect of dietary supple-ments of protected fat on the yield and fat concentration of ewe’s milk and on lamb growthrate. Anim. Prod. 42:455.

Horton, G. M J., J. E. Wohlt, D. D. Palatini,, and J. A. Baldwin. 1992. Rumen-protected lipidfor lactating ewes and their nursing lambs. Sm. Rum. Res. 9:27-36.

Marnet, P. G., S. Richard, D. Renaudeau, and J. Portanguen. 1999. Comparison between theoxytocin response to suckling, a mixed system of suckling and milking, and exclusive milk-ing in Lacaune ewe. . In: Milking and milk production of dairy sheep and goats. EAAPPubl. No. 95. p. 69-72. Wageningen Pers, Wageningen, The Netherlands.

McKusick, B. C., Y. M. Berger, and D. L. Thomas. 1999. Weaning and rearing systems forAmerican dairy sheep. J. Anim. Sci. 77(Suppl. 1):238.

Muir, D. D., D. S. Horne, A. J. R. Law, and W. Steele. 1993. Ovine milk. 1. Seasonal changesin composition of milk from a commercial Scottish flock. Milchwissenschaft: 48(7):363-366.

Rotunno, T., A. Sevi, R. Di Caterina, and A. Muscio. 1998. Effects of graded levels of dietaryrumen-protected fat on milk characteristics of Comisana ewes. Sm. Rum. Res. 30:137-145.

SAS. 1999. SAS User’s Guide (Release 7.0). SAS Inst. Inc., Cary, NC.Sklan, D. 1992. A note on production responses of lactating ewes to calcium soaps of fatty

acids. Anim. Prod. 55:288-291.Thomas, D. L., Y. M. Berger, and B. C. McKusick. 1999. Milk and lamb production of East

Friesian-cross ewes in the north central United States. In: Milking and milk production ofdairy sheep and goats. EAAP Publ. No. 95. p. 474-477. Wageningen Pers, Wageningen, TheNetherlands.

26

PROGRESS REPORT: A COMPARISON OF MARKET LAMBS SIRED BYSUFFOLK RAMS OF UNITED KINGDOM OR U.S. ORIGIN

David L. Thomas, Yves M. Berger, Brett C. McKusick, Randy G. Gottfredson,and Rob Zelinsky

Department of Animal Sciences, Spooner Agricultural Research Station, and ArlingtonAgricultural Research Station


Summary

A preliminary report on a trial in progress is presented. A flock of East Friesian crossbreddairy ewes was inseminated with semen from Suffolk rams of U.K. and U.S. origin in 1998. TheU.K. sires were high genetic merit rams from the U.K. Suffolk Sire Reference Scheme, and theU.S. sires were rams of high genetic merit from the National Sheep Improvement Program(NSIP). The inseminated ewes were naturally mated to non-NSIP U.S. Suffolk rams at the estrusfollowing their insemination. Lambs from the three different types of sires were compared forgrowth and carcass traits in 1999.

A desirable set of Suffolk-sired market lambs was produced. Lambs had an average 120 dayweight of 104 pounds and produced carcasses that averaged yield grade 3. There were no sig-nificant differences among sire groups for body weights at any age. However, there may havebeen a tendency for poorer growth from U.S. non-NSIP-sired lambs, for greater early growth inU.K.-sired lambs, and for greater later growth in U.S. NSIP-sired lambs. U.K.-sired lambs hadsuperior leg shape and quality grades when compared to U.S.-sired lambs.

Final conclusions from this year’s study can not be made until after the addition of more lategrowth and carcass data from the third slaughter group of lambs and a comprehensive analysis ofthe data. There is a good possibility that the trial will be repeated in 1999/2000 with most of thesame sires. Two years of data should allow more definitive conclusions to be made.

Introduction

The Suffolk breed originated in southeastern England in the counties of Norfolk, Suffolk,Essex, and Kent from the crossing of improved Southdown rams on the Old Norfolk sheep nativeto the area. The Suffolk was recognized as a breed by the Royal Agricultural Society of Englandin 1859. Suffolk sheep were first imported into the United States in 1888, later than the otherEnglish meat breeds. It was slow to gain acceptance among U.S. sheep producers; probablybecause other meat breeds were already well established. The breed started to gain widespreadacceptance from 1935 to 1945. During the 1960’s, Suffolk rams became the most popularterminal sire breed for the production of market lambs, and they continue in this role today. TheSuffolk breed annually registers more purebred individuals than any other sheep breed in theU.S.

27

Over the past 30 years in the U.S., there has been a large amount of selection emphasisplaced on large mature size and tall stature in the Suffolk breed. This has resulted in very rapid

lamb growth rates and an increase in the weights at which U.S. lambs are slaughtered. However,the U.S. Suffolk of today does not exhibit the muscularity in the legs and shoulders of its ances-tors. An exception to this trend has been the development of “wether type” lines of Suffolksheep in recent years to cater to the market lamb show industry that are well-muscled.

The Suffolk breed in the United Kingdom has not had the same selection emphasis on largestature as has the U.S. Suffolk, probably because the English and European markets don’t desirea heavy-weight market lamb. Instead, major selection emphasis has been placed on muscleconformation. Whereas many U.K. Suffolk sheep will have mature weights similar to U.S.Suffolks, they tend to be wider, shorter, larger-boned, and more muscular-appearing than U.S.Suffolks.

Both the U.S. and U.K. sheep industries have national genetic improvement programs. TheNational Sheep Improvement Program (NSIP) in the U.S. was established in 1986. It givesestimates of genetic value called Expected Progeny Difference (EPD) for a number of reproduc-tion, wool, and growth traits. Initially the estimates of genetic value for individuals were onlycomparable among individuals within a flock, but since 1995, the Suffolk breed has calculatedand published across-flock EPDs which allow the comparison of individuals both within andbetween flocks for estimates of genetic value.

Sheepbreeder is the name of the national genetic improvement program for sheep in the U.K.Its estimate of genetic value is Estimated Breeding Value (EBV; EBV = 2 x EPD). Estimates ofgenetic value are given for reproduction, growth, and carcass traits and are calculated on awithin-flock basis. In the late 1980’s, a number of U.K. Suffolk breeders organized themselvesinto the Suffolk Sire Reference Scheme (SSRS). The SSRS requires all members to be enrolledin Sheepbreeder and to artificially inseminate a specified number of their ewes each year to ramschosen by the SSRS (reference sires). These reference sires have a dual role. They creategenetic links across flocks which allow EBVs of individual animals to be compared both withinand across flocks. Also, since the reference sires are of high genetic value, their use speeds upthe rate of genetic improvement. Over 70 U.K. Suffolk breeders are members of the SSRS, andtheir flocks have made rapid rates of genetic improvement in growth and carcass traits since1990.

The main objective of this study was to compare the growth and carcass traits of lambs siredby U.K. Suffolk rams from the SSRS and U.S. Suffolk rams from the NSIP. A second objectivewas to compare the growth and carcass traits of lambs sired by U.S. Suffolk rams enrolled onNSIP and not enrolled on NSIP. The results in this report are preliminary. Growth andcarcass data are still being collected on some of the lambs, and a final statistical analysis ofthe data has not been conducted. While mean values of performance reported in this prelimi-nary paper will change somewhat with the addition of more data and after a more completestatistical analysis, the general trends seen here should remain.


Semen was made available from three U.K. rams selected by the SSRS and from five U.S.NSIP rams selected by the United Suffolk Sheep Association. The genetic evaluations of therams which provided the semen are presented in Tables 1 and 2.

28

Table 1. Genetic evaluations for the U.K. Suffolk rams

No. Scrapie 8 wk 21 wk Muscle Fat LeanSire progeny genotype wt., lb. wt., lb. depth, in. depth, in. index

Expected Progeny Differences

A 130 171RQ 4.38 7.06 .10 -.012 300B 101 171RR 3.17 8.04 .10 -.002 289C 1558 171RR 4.87 9.35 .10 .004 284

Average 596 4.14 8.15 .10 -.003 291

The SSRS reports EBVs, but I have converted their EBVs to EPDs by dividing by 2 andreported the EPDs in Table 1. The EPDs in Table 1 are relative to lambs born in 1990. Forexample, the three U.K. rams are expected to sire progeny that weigh 8.15 pounds more at 21weeks of age (~140 days) than the progeny of a ram of average genetic value born in 1990. TheEPDs in Table 2 for the U.S. NSIP rams are relative to the sires and dams of the first animalswith NSIP evaluations (founder animals). For example, the four NSIP rams with EPDs areexpected to sire progeny that weigh 4.9 pounds more at 120 days of age than the progeny of afounder ram of average genetic value. On average, the U.K. and U.S. NSIP rams are estimatedto have above average genetic values for all traits recorded.

In September and October 1998, 175 East Friesian crossbred ewes were synchronized andinseminated by laparoscopy with frozen-thawed semen. Similar numbers of ewes were insemi-nated with U.K. and U.S. NSIP semen, and one inseminator performed all the inseminations.Conception rates to artificial insemination were 74% for U.K. semen and 43% for U.S. NSIPsemen. Ewes were exposed to four non-NSIP Suffolk ram lambs in single-sire mating pens atthe estrus following insemination for a “clean-up” mating. The clean-up rams were purchasedfrom breeders in Wisconsin and were typical of Suffolk rams available to commercial producers.Therefore, three groups of lambs were born: from U.K. SSRS rams, from U.S. NSIP rams, andfrom U.S. non-NSIP rams.

Table 2. Genetic evaluations for the U.S. NSIP Suffolk rams

Expected Progeny Differences

% lamb Weaning Maternal Milk + 120-daySire crop wt., lb. milk., lb. growth, lb. wt., lb.

A 1.7 3.0 .3 1.8 5.5B 6.4 3.0 .1 1.6 5.7C -1.0 2.6 -.4 1.0 4.8D 9.0 2.1 .9 1.9 3.7E 1.4 3.1 .5 2.1 5.8

Average 3.5 2.8 .3 1.7 5.1

29

The East Friesian crossbred dams also were involved in another trial comparing two lambweaning systems. One-half of the lambs were removed from their dams a few hours after birthand raised on milk replacer. The other one-half of the lambs were raised by their dam for 30days but were separated from their dams overnight. Lambs were weaned from milk replacer orfrom their dam at approximately 30 days of age.

Males lambs were castrated. Lambs spent their entire life in the barn or a drylot with adlibitum access to a concentrate diet. A ground creep diet and hay was available preweaning.From weaning to approximately 70 days of age, lambs received a 19% crude protein diet ofrolled shelled corn and a high protein pellet. From 70 days of age to slaughter, a 12% crudeprotein diet of whole shelled corn and a high protein pellet was fed. No forage was offered to thelambs during the postweaning growth period. Lambs from all sire groups were mixed in thefeeding pens.

Lamb body weights were recorded at birth, at approximately 30, 60, 90, and 120 days of age,and at slaughter. The lambs are slaughtered at a weight endpoint in three groups. The first twogroups were slaughtered at an average live weight of 121 pounds, and the third group remains tobe slaughtered. Lambs were slaughtered at Wolverine Packing in Detroit, Michigan, and thefollowing carcass measurements were collected: hot carcass weight, leg conformation score (1 -15), 12th rib fat thickness, lower body wall thickness, loin eye area, and quality grade. Yieldgrade (.4 + (10 x 12th rib fat thickness)) and dressing percentage ((hot carcass weight/slaughterweight) x 100) were calculated.

Prior to statistical analyses, live weights taken at approximately 30, 60, 90, and 120 days ofage were adjusted for differences in age at weighing using actual average daily gains. Traitspresented in this report include birth weight, 60-day weight, 120-day weight, dressing percent-age, leg conformation score, loin eye area, 12th rib fat thickness, yield grade, and quality grade.Birth weights of lambs born dead or aborted were deleted from the analysis.

Data were analyzed using the general linear models procedure of the Statistical AnalysisSystem. The model for the body weight traits included the effects of sex of lamb (male, female),birth type of lamb (single, twin, triplet or greater), age of dam (2, 3, 4 years), rearing group oflamb (artificial, on the ewe), sire group (U.K., U.S. NSIP, U.S. non-NSIP), and individual sirenested within sire group. The individual sire nested within sire group mean square was used totest for differences among sire groups. The same model was used for the carcass traits but withthe addition of hot carcass weight fitted as a covariate so that carcass traits were adjusted fordifferences in carcass weight.

Results

Body weights of lambs are presented in Table 3. There were no significant differencesbetween sire groups for lamb body weights at birth, 60 days of age, or 120 days of age. How-ever, there was a tendency for U.S. non-NSIP-sired lambs to have lighter weights at all ages, forU.K.-sired lambs to be superior to U.S. NSIP-sired lambs for early growth, and for U.S. NSIP-sired lambs to be superior to U.K.-sired lambs for later growth. These differences, if found to besignificant with the addition of more data, are not surprising given the expected maturity patternsof U.S. and U.K. Suffolk sheep.

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Table 3. Body weights of lambs sired by U.S. or U.K. Suffolk rams

At birth At 60 days At 120 daysSire source No. Weight, lb.

aNo. Weight, lb.

aNo. Weight, lb.

a

U.S.NSIP

b36 12.4 ± .4 36 52.6 ± 2.4 25 106.8 ± 3.5

Non-NSIP 72 12.4 ± .3 70 51.2 ± 1.7 40 101.7 ± 2.8

U.K. - SSRSc

101 12.5 ± .2 98 55.4 ± 1.4 74 103.0 ± 1.8

a Differences between weights within a column are not statistically significant (P < .05).bNSIP = National Sheep Improvement Programc SSRS = Suffolk Sire Reference Scheme

Presented in Table 4 are the carcass traits of the lambs sired by the three sire groups. Unlikethe growth traits, there are significant differences among the sire groups for several of the carcasstraits. Dressing percentage varied from 52 to 53% among sire groups and was not statisticallydifferent. Leg conformation score was significantly greater for U.K. sired lambs (~13) comparedto U.S.-sired lambs (~12). The one unit of leg score superiority of the U.K.-sired lambs is anindication of the increased emphasis U.K. breeders have given to meat conformation in theirselection programs. However, the increased muscularity of U.K.-sired lambs in the leg was notreflected in significantly larger loin eyes. The lambs sired by the three sire groups had loin eyeareas that ranged from approximately 2.5 to 2.6 square inches. Measures of fatness (12th rib fatthickness and yield grade) show an interesting result. Both U.K.-sired and U.S. NSIP-siredlambs had similar amounts of rib fat, and both had significantly more rib fat than U.S. non-NSIP-sired lambs. It is difficult to explain this result. Carcass quality grade which increases with bothincreased fatness and increased conformation was significantly greater for U.K.-sired lambs(~low prime) compared to U.S.-sired lambs (~high choice).

Table 4. Carcass traits of lambs sired by U.S. or U.K. Suffolk rams

Dressing Leg Loin eye 12th rib Yield QualitySire source No. % score

aarea, in.

2fat, in. grade

bgrade

c

U.S.NSIP

d25 53.4 ± .5 11.9 ± .1

g2.46 ± .05 .28 ± .02

f3.2 ± .2

f11.9 ± .1

g

Non-NSIP 40 51.9 ± .4 11.8 ± .1g

2.55 ± .04 .24 ± .01g

2.8 ± .1g

11.8 ± .1g

U.K. - SSRSe

74 52.2 ± .3 12.9 ± .1f

2.61 ± .03 .30 ± .01f

3.4 ± .1f

12.9 ± .1f

aHigher values indicate more muscular legs; highest value is 15.bYield grade = .4 + (10 x 12th rib fat thickness).c11 = average choice, 12 = high choice, 13 = low prime.dNSIP = National Sheep Improvement ProgrameSSRS = Suffolk Sire Reference Schemef,g

Means within a column with different superscripts are different (P < .05).

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ConclusionsA desirable set of Suffolk-sired market lambs was produced in this study. Lambs had 60 day

weights of 51 to 55 pounds, 120 day weights of 102 to 107 pounds, and produced carcasses ofyield grade 2 to 3. There may have been a tendency for poorer growth from U.S. non-NSIP-siredlambs, for greater early growth in U.K.-sired lambs, and for greater later growth in U.S. NSIP-sired lambs. U.K.-sired lambs had superior leg shape and quality grades than U.S.-sired lambs.Differences in 12th rib fat thickness among sire groups was difficult to explain.

Final conclusions from this year’s study can not be made until after the addition of more lategrowth and carcass data from the third slaughter group of lambs and a comprehensive analysis ofthe data. There is a good possibility that the trial will be repeated in 1999/2000 with most of thesame sires. Two years of data should allow more definitive conclusions to be made.

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EFFECTS OF THREE WEANING AND REARING SYSTEMS ON COMMERCIALMILK PRODUCTION AND LAMB GROWTH



Abstract

A flock of 132 East Friesian (EF) crossbred ewes and their lambs were used to study theeffects of three weaning and rearing systems on milk production and lamb growth. During thefirst 30 days of lactation, ewes were either weaned from their lambs at 24 hr post-partum andthen machine milked twice daily (DY1), separated from their lambs for 15 hr from late afternoonthrough early morning and machine milked once daily in the morning (MIX), or not machinemilked and allowed unlimited access to their lambs (DY30). After 30 days, MIX and DY30ewes were weaned, and ewes in all three groups were machine milked twice daily. Commercialmilk yield and milk composition were recorded weekly until mid-lactation and then twicemonthly until dryoff. Average lactation length (suckling + milking periods) was 176 d and wassimilar between weaning systems. Total commercial milk production differed (P < .001) be-tween weaning systems (240, 205, and 149 L/ewe for DY1, MIX, and DY30 systems, respec-tively). During the first 30 days of lactation, commercial milk production, percentage of milk fatand protein, and somatic cell count (SCC) were lower (P < .05) for MIX ewes than for DY1ewes (42 and 70 L/ewe of milk; 3.24 and 4.88% milk fat; 5.36 and 5.52% milk protein; 44,700and 81,300 SCC, respectively). Approximately 30 days after lambing, commercial milk produc-tion, percentage of milk fat, and SCC were not different between weaning system groups, how-ever percentage of milk protein was higher (P < .05) for DY30 ewes (5.30%) compared to DY1and MIX ewes (5.07 and 5.11%, respectively). Litter size was a significant source of variationfor most lactation traits, however parity and proportion of EF breeding tended not to be signifi-cant. Ewes put on a legume-grass pasture in mid-lactation had greater (P < .005) milk produc-tion and lactated for more (P < .005) days than ewes fed in drylot. Growth traits of 272 twin-or-greater-born lambs sired by EF or Texel rams were estimated for three rearing systems. Lambswere either raised artificially (ART), allowed access to their dams for nine hours per day(LMIX), or allowed unlimited access to their dams (TRAD) for approximately their first 30 daysof age. Lamb weights at 30 days were similar, however at 120 d, TRAD lambs were heaviest (P< .01) compared to ART and LMIX lambs (47.8, 43.6, and 45.5 kg, respectively). From a sim-plified economic analysis, the MIX/LMIX system produced the greatest financial returns frommilk and lamb production.

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Introduction

Approximately 25% of the total lactational commercial milk yield of a dairy ewe isproduced during the first 30 days of lactation (Ricordeau and Denamur, 1962; Folman et al.,1966), a time when, traditionally, lambs are allowed to suckle their dams. For a dairy sheepenterprise, waiting until after 30 days post-partum to begin machine milking significantly affectseconomic returns as a result of reduced marketable milk (Geenty and Davison, 1982; Gargouri etal., 1993b) yet lamb growth may benefit from later weaning (Peters and Heaney, 1974; Gargouriet al., 1993a).

In an effort to maximize commercial milk yield and (or) lamb growth, a variety of wean-ing and rearing systems for dairy ewes and their lambs have been previously described. Innorthern Europe, particularly for the East Friesian breed (Flamant and Ricordeau, 1969), the eweis removed from her lambs within 24 h of birth and then machine milked twice daily until theend of lactation while the lambs are raised artificially. In the middle-East, e.g. in Israel with theAwassi breed (Folman et al., 1966a), shepherds with limited means to raise lambs artificiallyhave developed a partial-weaning system that allows for once daily milking of the ewes untilcomplete weaning, between 30 and 60 d post-partum, and then twice daily milking until the endof lactation. Typically lambs suckle ewes between 8 and 12 h per day until complete weaning.Finally a third scenario exists in New Zealand (Geenty and Davison, 1982) and the United States(Wolf and Tondra, 1994; McNalley, 1995; Thomas, 1996a); areas of the world where the produc-tion of lamb has traditionally been emphasized.

In the U.S., lambs are removed from their dams at approximately four weeks of age, andthen the ewes are machine milked twice daily for the remainder of lactation. The Americansheep dairy industry is young and as a consequence, effective weaning and rearing strategiesspecific to dairy-crossbred sheep have not yet been determined. The objectives of this studywere to compare commercial milk yield, milk composition and quality, and lamb growth forthree weaning and rearing systems in an experimental flock of East Friesian-cross sheep and toestimate their relative impact on economic returns.


Since 1993, East Friesian (EF) crossbred ewes have been produced from the matings ofEF-crossbred rams and Dorset-cross ewes. In the autumn breeding season of 1997, these eweswere mated to full-blood EF or Texel rams. Prior to the 1998 lactation, 132 of these EF-crosssecond and third parity ewes were assigned to one of three weaning-system treatments. Treat-ment one ewes (DY1, n = 42) were weaned from their lambs between 24 and 36 hr post-partum,and then machine milked twice daily for the remainder of lactation. Treatment two ewes (MIX, n= 48), beginning 24 hr post-partum, were separated from their lambs at 1700 each day andmilked once daily every morning at 0600. After the morning milking, ewes were returned totheir lambs. MIX ewes were milked twice daily following permanent weaning of their lambs at

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approximately 28 days of age. Treatment three ewes (DY30, n = 42) were initially not milkedand allowed constant access to rear their lambs. After approximately 32 days post-partum, theewes were weaned from their lambs and milked twice daily.

The experimental ewes gave birth to 289 lambs. Because there were relatively fewsingle-born lambs, they were excluded from the lamb analyses. Fourteen lambs were born deador died at birth, providing 258 live lambs for allocation to three rearing system treatments whichgenerally corresponded to their dams’ weaning system treatment. All lambs from DY1 ewes andsome lambs from MIX and DY30 ewes were raised artificially on milk replacer dispensed from alamb-bar (lamb treatment = ART, n = 93). Lambs raised artificially were weaned from milkreplacer at an average age of 24 days. Lambs reared naturally by MIX ewes (lamb treatment =LMIX, n = 78) and by DY30 ewes (lamb treatment = TRAD, n = 87) were weaned at averageages of 28 and 32 days, respectively.

Machine milking of ewes took place in a 12 x 2 milking parlor with indexing stanchionsand a high-line pipeline system. Milk production was recorded weekly during early lactation andthereafter, twice a month using a Waikato milk meter jar. Individual milk production was re-corded on Monday evening and Tuesday morning, and samples for composition analysis weretaken on Tuesday morning. Milk composition analysis for percentage of fat, percentage ofprotein, and Fossomatic® somatic cell count was performed by a State of Wisconsin certifiedlaboratory. The terms pre-, peri, and post-weaning were used to describe the stages of lactation:days 1 to 30, 31 to 45, and 46 post-partum to the end of lactation, respectively. Total days inlactation was defined as the number of days from parturition to dryoff. Milk production for eachstage of lactation was calculated based on the weekly testings. Milk fat and protein percentagesfor each stage were calculated as weighted averages. Somatic cell counts were transformed tobase-10 logarithms and then averaged over each stage of lactation. Lambs were weighed atbirth, at weaning from their dams (LMIX and TRAD lambs) or from milk replacer (ART lambs),and prior to slaughter, and adjusted 30-day and 120-day weights were calculated. Least squaresmeans analysis of variance was conducted with the GLM procedure of SAS (1999). Sources ofvariation accounted for in the ewe models were: weaning system (DY1, MIX, or DY30), parity(second or third), ewe breed (≤ 1/4 EF or > 1/4 EF), litter size (one, two, and three or greater),mid- to late-lactation nutrition (pasture or drylot), and 1997 adjusted milk production (< 150 L,150 to 200 L, or > 200 L). Sources of variation included in the lamb models were: rearingsystem (ART, LMIX, or TRAD), sex (female or intact-male), birth type (twin, or triplet andgreater), breed of sire (Texel or EF), breed of dam (≤ 1/4 EF or > 1/4 EF), and age of dam (twoor three years). Lamb birth weight was modeled as a covariate in the analyses of 30-day and120-day weights. This report presents the results of data collected during the 1998 lactation.

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For economic comparisons of the three weaning and rearing systems, calculations werebased on the production of one ewe and her 2.19 lambs (the average number of lambs born [n =289] to ewes lambing that were allocated to experimental treatments [n = 132]). The pricereceived for commercial milk and for live lamb marketed at 120 d of age was $.1.32/kg and$1.87/kg, respectively. The increased expenses for the DY1 and MIX ewes over DY30 ewesincluded the labor to milk the DY1 and MIX ewes during the first 30 d of lactation ($.27/ewe/milking) during which time the DY30 ewes nursed their lambs and were not milked. An addi-tional expense for the MIX ewes was the extra labor to separate the lambs from the ewes onceper day for 30 days (15 min/day/two people at $8.00/hr/person) which totaled $2.50/ewe. Theincreased expenses for the ART lambs over the TRAD and LMIX lambs included milk replacer(8.4 kg/lamb at $2.51/kg), labor to feed the lambs (1.2 hr/lamb at $8.00/hr), and supplies ($.34/lamb) which totaled $31.03/lamb.

Results

Milk yield and lactation length. Lactation curves for commercial milk production of thethree weaning systems are displayed in Figure 1. Liters of commercial milk per ewe producedover the entire lactation by DY1 and MIX systems was 61 and 38% greater (P < .001) than forthe DY30 system, the system traditionally used by most U.S. sheep dairies (Table 1). Milkproduction was similar between systems during the post-weaning period, however large differ-ences (P < .0001) were observed during the pre-weaning period (70, 42, and 0 L/ewe for DY1,MIX, and DY30 systems, respectively). During the peri-weaning period, DY1 and MIX ewesproduced similar amounts of commercial milk, but both produced more (P < .05) than DY30ewes (32, 34, and 28 L, respectively). Length of lactation was similar between weaning systems,however inherent to the DY30 system was a loss (P < .0001) of 38 or 31 d of machine milkingduring early lactation when 20 to 30% of total commercial milk yield is obtained relative to theDY1 and MIX systems, respectively (Table 1). Average daily commercial milk yield was great-est (P < .005) for DY1 ewes and greater (P < .005) for MIX ewes than for DY30 ewes.

Weaning system by nutrition interaction was significant for total commercial milk yieldand average daily commercial milk yield traits (Table 2). DY1 and DY30 ewes produced similaramounts of milk regardless of nutrition. MIX ewes, however produced 32% more milk (P < .05)on pasture than in the drylot.

Milk composition and quality. Milk fat percentage tended (P < .05) to rise as lactationprogressed (Figure 2). Averaged over the entire lactation, MIX ewes’ milk fat content (4.65%)was lower (P < .05) than that of the DY1 and DY30 systems (5.05 and 4.98 %, respectively,Table 3). The differences between systems were greatest during the pre-weaning period whereDY1 ewes (4.88%) had 1.5 times higher (P < .0001) percentage of milk fat than MIX ewes(3.24%) and during the peri-weaning period when DY30 ewes (4.21%) had lower (P < .01)percentage of milk fat compared to DY1 and MIX ewes (4.90 and 4.78%, respectively). Post-weaning percentage of milk fat was not different among weaning systems. Kilograms of fat washighest for DY1 ewes, intermediate for MIX ewes, and lowest for DY30 ewes (P < .0001).

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Milk protein percentage was highest during the pre-weaning stage, decreased throughmid-lactation, and then increased for the remainder of lactation (Figure 3). Average proteinpercentage over the entire lactation was similar between weaning systems (Table 2), howeverdifferences (P < .05) were present during the pre-weaning and post-weaning periods. Kilogramsof protein was highest for DY1 ewes, intermediate for MIX ewes, and lowest for DY30 ewes (P< .0001). SCC did not differ significantly from beginning to the end of lactation (Figure 4).During the pre- and post-weaning stages, SCC was lowest (P < .01) for MIX ewes compared tothe other two weaning systems; post-weaning SCC was not different (Table 2).

Lamb growth. The significant differences in birth weight (Table 4) between lamb rearinggroups were unexpected since ewes, and therefore lambs, were assigned to treatment groupsprior to lambing. Therefore, lamb birth weight was included as a covariate in the analyses of theother lamb growth traits. Growth and weight of lambs up to 30 d were not different betweenrearing groups. At 120 d, TRAD lambs had grown 13% faster and weighed 10% more (P < .01)than ART lambs. LMIX lambs were intermediate in 120-d weight to the other two groups,however, growth of LMIX lambs from 30 to 120 d was similar to that of TRAD lambs.

Discussion

Milk yield and lactation length. MIX ewes during the pre-weaning period were machinemilked once per day and produced only 40% less commercial milk compared to DY1 ewes thatwere milked twice per day (Table 1). These results imply that physiological and hormonal main-tenance of lactation for MIX ewes may have been superior to the other two groups, at leastduring early lactation. Other authors who have studied partial weaning systems have determinedthat the oxytocin-mediated-milk-ejection is impaired compared with ewes that were exclusivelymachine milked (Marnet et al., 1999b; Negrão and Marnet, 1998). However, more frequent andcomplete udder evacuations prevent overdistention and physical crushing of the alveoli(Labussière et al., 1978), and quite possibly reduce local concentrations of a feedback inhibitorof lactation (Wilde et al., 1987, 1995). These factors could compensate for the deleterious effectsof poor oxytocin release on commercial milk yield for the MIX ewes (Marnet, 1997; Marnet etal., 1999b). Furthermore, MIX ewes produced 7 and 20% more commercial milk during theperi-weaning period than DY1 and DY30 ewes, respectively (Table 1), and therefore appeared tobe least affected by the negative effects of weaning on milk production that have been previouslyreported (Ricordeau and Denamur, 1962; Gargouri et al., 1993b; Bocquier et al., 1999). DY1and MIX ewes produced 13 and 6%, respectively, more milk than DY30 ewes during the post-weaning period (Table 1), however the differences between systems were not significant. Therelatively poor performance of the DY30 ewes could be due to a stronger maternal bond as aresult of spending longer and uninterrupted periods of time with their lambs (Marnet et al.,1998a,b). The early effects of weaning system are large enough to account for most of thedifferences in commercial milk yield between groups over the entire lactation (Louca, 1972;Geenty and Davison, 1982; Knight et al., 1993), yet do not significantly affect lactation length(Lawlor et al., 1974; Geenty, 1980; Knight et al., 1993).

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Milk composition and quality. Percentage of fat and protein during the pre- and peri-weaning stages of lactation were suppressed in the two groups of ewes that were allowed partialor full access to their lambs during the first 30 d of lactation which is consistent with otherreports (Ricordeau and Denamur, 1962; Papachristofourou, 1990; Gargouri et al., 1993a; Kremeret al., 1996; Fuertes et al., 1998). Following complete weaning of these ewes from their lambs,milk composition eventually returned to the levels of the DY1 ewes. The most likely explana-tion for this phenomenon is impairment to the milk-ejection reflex which occurs when ewes areallowed to bond with their lambs (Labussière 1993; Marnet 1997; Marnet et al., 1999a,b). Milkfat droplets in the ewe are large (Muir et al., 1993) and exceed the diameter of the intralobularsecondary ducts therefore requiring adequate myoepithelial contraction for their expulsion intothe cistern. Without optimum milk-ejection reflex, milk fat (and to some degree, milk protein) istrapped in the udder, and the milk extracted by the machine has a low fat content. Besides theobvious economic consequences of residual fat retention, it has been hypothesized that certainfatty acids present in alveolar milk might inhibit further fat synthesis of neighboring cells duringmoments of stagnation (Labussière et al., 1978). The MIX and DY1 systems yielded approxi-mately 38 and 65% respectively, more kilograms of fat and protein than the DY30 system (P <.0001), which was largely due to the strong differences in overall commercial milk yield. Milkquality as judged by SCC was superior for MIX ewes compared to the other two weaning sys-tems. This would imply that perhaps more frequent and (or) complete udder evacuations associ-ated with a partial weaning/milking system are more desirable with respect to udder health(Barillet, 1989). Furthermore, machine milking beginning within 24 hr post-partum is perhapsmore traumatic on ewes’ udders and may allow greater entry of pathogens into the udder thanwould the suckling of a lamb during the first 30 d of lactation (Bergonier et al., 1996). Duringthe peri-weaning period, SCC was significantly elevated for the DY30 system, the time whenewes were being weaned of multiple, fast-growing lambs and were also making the transition totwice-daily machine milking. Although SCC in the present experiment were extremely lowcompared to other reports in the literature for ewes (Ranucci and Morgante, 1996), it wouldappear that at least during early lactation, SCC are influenced by weaning system. However,after complete weaning, differences between systems were no longer significant.

The weaning system by nutrition interaction is difficult to explain. It is possible thatMIX ewes had a greater udder secretory capacity than either the DY1 or DY30 ewes as a resultof both nursing lambs and being machine milked. This may have physiologically prepared themto better respond to the increased nutritive value of pasture with increased milk production.

Lamb growth. Adjusted 30 d weight and adjusted daily gain from birth to 30 d were similarbetween lamb groups which is in contrast to previous studies that have concluded that lambs rearednaturally by their dams have superior growth and weight by 30 d compared to partial weaning sys-tems (Hadjipanayiotou and Louca, 1976) or artificial rearing systems (Peters and Heaney, 1974;Knight et al., 1993). Furthermore, the results of the present experiment also differ with previousreports which concluded that rearing system had no effect on final lamb weight (Louca, 1972; Petersand Heaney, 1974; Gargouri et al., 1993a,b) or growth rate (Peters and Heaney, 1974; Knight et al.,1993). The ART system was detrimental to both lamb growth and weight from 30 to 120 d. Lambgrowth rate was somewhat lower than what

38

has been observed for lambs artificially raised at the Spooner Agricultural Research Station inprevious years under similar management conditions (320 to 360 g/d; Berger and Schlapper,1993). LMIX lambs seemed to have compensatory weight gain during this period which hasbeen previously confirmed in growing animals with prior nutrition limitations (Peters andHeaney, 1974; Black, 1983).

Rearing System × Birth Type Interactions. A significant interaction between rearingsystem and birth type was found for 30-d weight and average daily gain from birth to 30 d (Table5). Twin-born lambs reared by the LMIX system had significantly inferior 30-d weights andgrew slower from birth to 30 d than twin-born lambs reared by either the ART or TRAD systems(14.4, 15.3, and 16.1 kg, respectively; 322, 352, and 378 g/d, respectively, Table 5). Rearingsystem was not a significant source of variation for lamb growth traits of triplet-or-greater-bornlambs and were similar to growth traits for the twin-born lambs raised by the LMIX system.These findings imply that lambs raised by the LMIX system are no more disadvantaged withrespect to growth than triplet-or-greater-born lambs raised under any of the three rearing systems.

Relative economic returns. Table 6 summarizes the returns associated with combinedcommercial milk and lamb production for the DY1 and MIX system relative to the DY30 sys-tem. The MIX/LMIX and DY1/ART systems offer 15.6 and 6.6%, respectively, more returnsthan the DY30/TRAD system. More days of machine milking for the DY1 and MIX systemsenabled returns in ewe milk value ($108.27 and $67.15, respectively) to overcome their de-creases in net lamb value, relative to the DY30 system (-$83.27 and -$8.38, respectively). Over-all lamb mortality in the present study was 11%, and was not significantly different betweenrearing system treatment groups. Other authors have reported lamb mortality of artificiallyraised lambs to be between 15 and 35% (Peters and Heaney, 1974; Knight et al., 1993). Mortal-ity rate would have to be 25% or greater for the DY1 system to offer returns equal or less thanthat of the DY30 system. In this experiment, milk purchase price was constant ($1.32/kg),regardless of milk composition or quality. It is reasonable to assume that in the future, producerswill receive lower prices for milk of poorer fat and protein content or higher somatic cell count.Because of the milk fat suppression observed during the pre-weaning period for the MIX ewes,milk purchase price during early lactation may be affected. Milk from MIX ewes would have tobe worth only $1.17/kg and $1.06/kg to equal the returns of the DY1 and DY30 systems, respec-tively.

Implications

Weaning and rearing systems for dairy sheep producers attempt to maximize commercialmilk yields without seriously disadvantaging lamb growth, and are thus markedly different fromthe systems used in traditional lamb and wool operations. Thus far, weaning at 30 d has been themost common system used by American dairy shepherds. The results of this experiment demon-strate that two other weaning systems, a partial suckling/milking system and a 24 hr weaningsystem, offer significant increases in commercial milk production and greater economic returnsthan a 30-day weaning system.

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Table 1. Least squares means (±SE) for milk yield lactation traits of the three weaning systems

Weaning System

Trait DY1 MIX DY30

Number of ewes 42 48 42

Commercial milk yield, L/ewepre-weaning 69.6 ± 2.3a 42.4 ± 2.3b -

peri-weaning 31.5 ± 1.1a 33.8 ± 1.1a 28.1 ± 1.2b

post-weaning 138.1 ± 6.1 129.9 ± 6.0 122.1 ± 6.5total 239.6 ± 7.6a 205.4 ± 7.51b 148.6 ± 8.2c

Lactation length, d 177.7 ± 5.3 171.0 ± 5.0 169.4 ± 5.9

Machine milking period, d 176.7 ± 5.3a 170.0 ± 5.0a 138.9 ± 6.0b

Average daily commercial milkyield, L/d 1.33 ± .03a 1.20 ± .03b 1.05 ± .04c

a,b,c Within a row, means lacking a common superscript letter are different (P < .05).

Table 2. Least squares means (±SE) for total commercial milk yield and average daily milk yield by weaningsystem - nutrition combinations

Weaning System

Trait Nutrition DY1 MIX DY30(42)§ (48) (42)

Commercialmilk yield, L

pasture 243.6 ± 11.4a 234.2 ± 9.83a 156.9 ± 10.4bc

drylot 235.6 ± 10.4a 176.5 ± 10.4b 140.4 ± 11.8c

Average dailymilk yield, L/d

pasture 1.33 ± .05a 1.31 ± .04a 1.06 ± .05b

drylot 1.33 ± .04a 1.10 ± .05b 1.04 ± .06b

§ Number of ewes.a,b,c Within an independent trait, means lacking a common superscript letter are different (P < .05).

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Table 3. Weighted† least squares means (±SE) for milk composition and quality traits of the three weaning systems

Weaning System

Trait DY1 MIX DY30

Number of ewes 42 48 42

Milk fat, %pre-weaning 4.88 ± .16a 3.24 ± .18b -

peri-weaning 4.90 ± .14a 4.78 ± .15a 4.21 ± .17b

post-weaning 5.14 ± .10 5.25 ± .11 5.30 ± .12total 5.05 ± .10a 4.65 ± .10b 4.98 ± .12a

Total milk fat, kg 12.3 ± .52a 10.2 ± .58b 7.45 ± .64c

Milk protein, %pre-weaning 5.52 ± .06a 5.36 ± .06b -

peri-weaning 5.12 ± .07 5.04 ± .06 5.07 ± .07post-weaning 5.07 ± .07a 5.11 ± .06a 5.30 ± .07b

total 5.23 ± .06 5.14 ± .06 5.23 ± .06

Total milk protein, kg 13.0 ± .47a 10.9 ± .46b 7.86 ± .49c

Somatic cell count, log unitspre-weaning 4.91 ± .06a 4.65 ± .06b -

peri-weaning 5.02 ± .07ab 4.86 ± .07a 5.18 ± .08b

post-weaning 4.88 ± .06 4.81 ± .06 4.95 ± .06

† For percentages of milk fat and protein.a,b,c Within a row, means lacking a common superscript letter are different (P < .05).

Table 4. Least squares means (±SE) for lamb growth traits of the three rearing systems

Rearing System

Trait ART LMIX TRAD

Number of lambs reared 93 78 87

Birth weight, kg 4.58 ± .11a 4.37 ± .27a 5.00 ± .15b

Weaning age, d 24.2 ± .60a 27.9 ± 1.0b 31.5 ± .90c

Adjusted 30-d weight, kg 14.9 ± .27 14.3 ± .39 15.2 ± .38

Adjusted daily gain frombirth to 30 d, g/d 338.7 ± 8.92 319.4 ± 13.1 348.6 ± 12.5

Adjusted 120-d weight, kg 43.6 ± .84a 45.5 ± 1.2ab 47.8 ± 1.2b

Adjusted daily gain from30 to 120 d, g/d 319.1 ± 8.60a 346.4 ± 12.8b 361.9 ± 12.3b

a,b,c Within a row, means lacking a common superscript letter are different (P < .05).

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Table 5. Least squares means (±SE) for lamb growth traits by rearing system - birth type combination

Birth Type

Trait Rearingsystem twin ≥ triplet

Adjusted 30-d weight, kgART 15.3 ± .32a 14.5 ± .37b

LMIX 14.4 ± .42b 14.3 ± .49b

TRAD 16.1 ± .46a 14.3 ± .40b

Weight gain from birthto 30 d, g/d

ART 352.1 ± 10.6a 325.4 ± 12.3b

LMIX 322.1 ± 14.0b 316.8 ± 16.4b

TRAD 377.8 ± 15.3a 319.4 ± 13.3b

a,b Within an independent trait, means lacking a common superscript letter are different (P < .05).

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Gargouri, A., G. Caja, X. Such, A. Ferret, R. Casals, and S. Peris. 1993b. Evaluation of a mixedsystem of milking and suckling in Manchega dairy ewes. Proc. of the Fifth InternationalSymposium on the Machine Milking of Small Ruminants, Budapest, Hungary, May 14-20.484-499.

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Jandal, J. M. 1996. Comparative aspects of goat and sheep milk. Sm. Rum. Res. 22:177-185.Knight, T. W., D. S. Atkinson, N. A. Haack, C. R. Palmer, and K. H. Rowland. 1993. Effects of

suckling regime on lamb growth rates and milk yields of Dorset ewes. N. Z. J. Agric. Res.36:215-222.

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Labussière, J., J. F. Combaud, and P. Pétrequin. 1978. Influence respective de la fréquencequotidienne des évacuations mammaires et des stimulations du pis sur l’entretien de lasécrétion lactée chez la brebis. Ann. Zootech. 27(2):127-137.

Labussière, J. 1993. Physiologie de l’éjection du lait: Conséquences sur la traite. In: Biologiede la Lactation. pp. 259-294. Institut National de la Recherche Agronomique, Services desPublications, Versailles, France.

Lawlor, M. J., A. Louca, and A. Mavrogenis. 1974. The effect of three suckling regimes on thelactation performance of Cyprus fat-tailed, Chios and Awassi sheep and the growth rate oflambs. Anim. Prod. 18:293-299.

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Marnet, P. G., J. A. Negrão, P. Orgeur, and L. LeBellego. 1999a. Effect of inhibition of maternalbehavior by peridural anesthesia on the endocrine response to milking during the first daysafter parturition. In: Milking and milk production of dairy sheep and goats. EAAP Publ. No.95. p. 65-68. Wageningen Pers, Wageningen, The Netherlands.

Marnet, P. G., S. Richard, D. Renaudeau, and J. Portanguen. 1999b. Comparison between theoxytocin response to suckling, a mixed system of suckling and milking, and exclusive milkingin Lacaune ewe. In: Milking and milk production of dairy sheep and goats. EAAP Publ. No.95. p. 69-72. Wageningen Pers, Wageningen, The Netherlands.

McNalley, J. 1995. The economics of producing milk from dairy sheep. Proc. of the GreatLakes Dairy Sheep Symposium, March 30, 1995, Madison, WI, USA. 1-5.

Muir, D. D., D. S. Horne, A. J. R. Law, and W. Steele. 1993. Ovine milk. 1. Seasonal changesin composition of milk from a commercial Scottish flock. Milchwissenschaft: 48(7):363-366.

Negrão, J. A. and P. G. Marnet. 1998. Release of oxytocin, prolactin, and cortisol by a mixedsystem of suckling and milking. Liv. Prod. Sci. 1497:xx.

Papachristoforou, C. 1990. The effects of milking method and post-milking suckling on ewemilk production and lamb growth. Ann. Zootech. 39:1-8.

Peters, H. F. and D. P. Heaney. 1974. Factors influencing the growth of lambs reared artificiallyor with their dams. Can. J. Anim. Sci. 54:9-18.

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Ricordeau, G. and R. Denamur. 1962. Production laitière des brebis Préalpes du Sud pendantles phases d’allaitement, de sevrage et de traite. Ann. Zootech. 11(1):5-38.

SAS Institute Inc. 1995. SAS/STAT User’s Guide. Version 6.11. SAS Institute Inc. Cary, NC.Thomas, D. L. 1996a. Dairy sheep basics for beginners. Proc. of the Second Great Lakes Dairy

Sheep Symposium, March 28, Madison, WI, USA. 65-71.Thomas, D. L. 1996b. Opportunities for genetic improvement of dairy sheep in North America.

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Wilde , C. J., D. T. Calvert, A. Daly, and M. Peaker. 1987. The effect of goat milk fractions onsynthesis of milk constituents by rabbit mammary explants and on milk yield in vivo.Biochem. J. 242:285-288.

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PRELIMINARY RESULTS: EFFECTS OF UDDER MORPHOLOGY ONCOMMERCIAL MILK PRODUCTION OF EAST FRIESIAN CROSSBRED EWES



Abstract

Udder and teat morphology measurements were taken at approximately 7.5 hr after thea.m. milking for 131 East Friesian (EF) crossbred ewes at an average of 71 d in lactation. Addi-tionally, milking time was recorded for each ewe during two evening and morning milkings.Average daily milk production, milking time, percentage of milk fat, percentage of milk protein,and somatic cell count were 2 L/ewe/day, 174 sec, 5.07%, 4.77%, and 56,250, respectively.When compared to reports in the literature on other dairy breeds of sheep, our EF crossbred eweshad larger udder width (14.6 cm), cistern height (2.97 cm), and teat angle (58.3°); similar uddercircumference (45.2 cm) and teat width (1.64 cm); and smaller udder height (14.6 cm) and teatlength (2.6 cm). Regression coefficients were calculated for these udder and teat measurementson various lactation traits. Ewes with greater udder circumference and udder height had greatercommercial milk yield. Greater udder length, udder height, and cistern height were associatedwith increased milking time. Cistern height was positively associated with percentage of milkfat. In conclusion, ewes having larger udders with more cistern located below the teat canal exitare predicted to have higher milk yield, higher percentage of milk fat, and take longer to machine milk.

Introduction

Dairy sheep production in the United States is becoming an economically viable enter-prise. Since the importation of the East Friesian (EF) breed in the early 1990’s, relatively littlegenetic selection has been possible due to the limited amounts of dairy sheep germ plasm avail-able. Therefore, many producers may have been milking ewes that are relatively unadapted tomachine milking. High-percentage EF ewes and rams are now available to producers, andgenetic selection programs need to be implemented to further adapt the EF dairy ewe to anAmerican production setting. Producers who milk sheep are well aware of the individual varia-tion in udder size, shape, and teat placement, and the ramifications that udder conformation mayhave on milk yield and machine milking time.

Sagi and Morag (1974), Jatsch and Sagi (1979), and Gootwine et al. (1980) with Awassiand Assaf ewes performed some of the earliest work with dairy ewe udder morphology in Isreal.Udder anatomy and morphologic parameters of Lacaune, Sarda, Manchega, Tsigaya, andKaragouniko dairy ewes have been studied in the Mediterranean basin, initially under a protocolissued by FAO, and have been reviewed by Labussière et al. (1981) and Labussière (1983, 1988).Further work has been done in France with the Rouge de l’Ouest (Malher and Vrayla-Anesti,1994) and Lacaune (Marie et al., 1999); in Spain with the Churra (de la Fuente et al., 1996;Fernández et al., 1995, 1997), Laxta, Manchega, and Lacaune (de la Fuente et al., 1999; Rovai etal., 1999; Such et al., 1999); in Italy with the Sarda (Carta et al., 1999); in Greece with the Chios(Mavrogenis et al., 1988); and in Poland with the Zelazna (Charon, 1990). Tables 1 and 2 sum-marize the breed differences in udder and teat morphology measurements from some of theabove references.

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Morphology traits, such as udder circumference, udder shape, teat length, and teat width,are moderately heritable (Gootwine et al., 1980; Mavrogenis et al., 1988; Fernández et al., 1997;Carta et al., 1999) and are significantly correlated with milk yield (Labussière et al., 1981;Labussière, 1988; Fernández et al., 1995, 1997; Carta et al., 1999; Rovai et al., 1999). Moreover,it is plausible that these traits not only influence milk yield, but also milk composition andmilking time. The objectives of this experiment were to quantitatively assess the variation inudder morphology in our EF crossbred dairy flock and to estimate the relationship between avariety of udder measurements and commercial milk production and milking time.

Table 1. Summary of breed differences cited in the literature with respect to uddermorphology measurements

Breed

Lacaune Rouge de Manchega Churra Sarda ChiosMeasurement l’Ouest

Udder circumference, cm 46.56 48.47a

36.07b

Udder width, cm 13.54 11.94 12.26

Udder length, cm 9.361 9.265 8.382 8.132 10.72

7.012 10.52 9.306

11.33 11.43

11.04 9.104

Udder height, cm 17.83 17.23 23.47

17.74 13.44

Cistern height, cm 1.321 1.385 .692 1.882 3.192

1.932 1.602 1.486

2.003 1.553

2.094 1.104

1 Labussière et al. (1981) in France. 65 to 80 d in milk. Measured 8 hr after the a.m. milking.2 Reviewed by Labussière et al. (1988). 50 d in milk. Measured 8 hr after the a.m. milking.3 Rovai et al. (1989) in Spain. 10, 30, 60, and 120 d in milk. Measured 2 hr prior to p.m. milking.4 Such et al. (1999) in Spain. 110 d in milk. Measured 4 hr after a.m. milking5 Malher and Vrayla-Anesti (1994) in France. 22 to 110 d in milk. Measured immediately prior to milking.6 Fernandez et al. (1995) in Spain. 30, 60, 90, and 120 d in milk. Measured immediately prior to a.m. milking.7 Mavrogenis et al. (1988) in Cyprus. 50 d in milk. Measured immediately prior toa or afterb milking.

Table 2. Summary of breed differences cited in the literature with respect to teatmorphology measurements

Breed

Lacaune Rouge de Manchega Churra Sarda ChiosMeasurement l’Ouest

Teat angle, deg 41.81 26.55 43.42 50.72 67.22

48.02 46.12 50.46

44.13 42.53

52.34 45.64

Teat length, cm 3.251 3.195 3.072 2.612 2.722 4.267

3.062 2.882 3.836

2.913 3.363

3.084 3.284

Teat width, cm 1.531 1.535 1.792 1.602 1.602 2.307

1.432 1.532 1.936

1.323 1.513

1.594 1.664

Teat position score, no 2.851 3.105 3.002 3.402 3.702

3.202 2.504 3.646

2.704

1 Labussière et al. (1981) in France. 65 to 80 d in milk, measured 8 hr after the a.m. milking.2 Reviewed by Labussière et al. (1988). 50 d in milk, measured 8 hr after the a.m. milking.3 Rovai et al. (1989) in Spain. 10, 30, 60, and 120 d in milk, measured 2 hr prior to p.m. milking.4 Such et al. (1999) in Spain. 110 d in milk, measured 4 hr after a.m. milking5 Malher and Vrayla-Anesti (1994) in France. 22 to 110 d in milk, measured immediately prior to milking.6 Fernandez et al. (1995) in Spain. 30, 60, 90, and 120 d in milk, measured immediately prior to a.m. milking.7 Mavrogenis et al. (1988) in Cyprus. 50 d in milk, measured immediately priora or afterb milking.


Between May 12 and 14, 1999, 131 EF crossbred dairy ewes were evaluated for udderanatomy and machine milking time. Ewes were at an average of 71 d in lactation and wereproducing approximately 2 L/d of commercial milk. Udder measurements (Figure 1 and 2) weretaken once on every ewe at approximately 7.5 hours after the morning milking (1230 to 1430) byone technician. A second technician photographed a caudal view of every ewe’s udder. A thirdtechnician recorded the data. Ewes in the drylot (n = 59) were measured on May 12, and ewesgrazing a kura-clover pasture during the day (n = 72) were measured on May 13. Udder anatomyand morphology data collected were:

1. Udder circumference (ucirc): a scrotal circumference tape was placed around the widestportion of the udder.

2. Udder width (uwid): a large caliper was used to measure the distance between the widestlateral points of the udder.

3. Udder length (uleng): a large caliper was used to measure the distance between the mostcranial and caudal points of udder attachment at the intramammary groove.

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deleterious effects from the stress of measuring the ewes. Total commercial lactation milk yieldto May 12 was calculated by using a previously reported formula (Thomas, 1996). Milk fat andprotein yield for individual ewes were calculated weekly or bi-weekly by multiplying a ewe’stest-day yield with her corresponding percentage of fat or protein by the number of days betweentest days .

4. Udder height (uht): a large caliper was used to measure the distance between the perinealattachment of the udder and the perpendicular of the site of teat attachment.

5. Cistern height (cisht): a T-square was used to measure the distance between the perpendicu-lar of the site of teat attachment and the bottom of the right and left cisterns.

6. Teat angle (tang): with a plumb line hung behind the ewe, a photograph was taken of everyewe. From these photographs, right and left teat angles relative to the vertical were drawn,and then measured with a protractor.

7. Teat length (tleng): a small clear ruler was used to measure the distance between the tip ofthe teat and its attachment to the udder for both right and left teats.

8. Teat width (twid): a small clear ruler was used to measure the distance between the twolateral borders of the teat at the midpoint of the teat length measurement, for both right andleft teats.

9. Teat position score (tpos): a subjective score from 1 to 5 was used to evaluate lateral teatplacement for both right and left teats (1=caudal, 2=vertical, 3=slightly cranial, 4=cranial,5=horizontal).

Ewes were machine-milked in a 12 x 2 milking parlor with indexing stanchions and a high-line pipeline system (Alfa Laval-Agri, Tomba, Sweden) by two technicians. Machine-milkingsettings included a pulsation rate of 180/min, a ratio of 50:50, and a vacuum level of 38 kPa.Milking times were recorded for all ewes during the morning milkings (0600) of May 13 and 14,and for the evening milkings (1700) of May 12 and 13. Each ewe was individually timed with aseparate stopwatch by a third technician. The stopwatch was started as the teat cups were beingplaced on the teats, the ewe was machine milked and machine stripped, and then the stopwatchstopped at the moment the teat cups were removed from the udder. Commercial milk yield (a.m.and p.m.) was measured weekly or bi-weekly with a Waikato milk meter. Milk compositionsamples were taken weekly or bi-weekly and submitted to a State of Wisconsin certified dairylaboratory for analysis of percentage of milk fat, milk protein, and Fossomatic® somatic cellcount. The last test day data included in this study was collected on May 11-12 to avoid any

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Figure 1. Caudal schematic view of a ewe udder demonstrating anatomical and morphologicmeasurements taken. Udder height (uht), udder width (uwid), cistern height (cisht), teat angle(tang), teat length (tleng), and teat width (twid).

Figure 2. Lateral schematic view of a ewe udder demonstrating anatomical and morphologicmeasurements taken. Udder length (uleng) and teat position score (tpos).

uwitan

uh

cisht

tleng

twi

12 3

4

5

uleng

L R

Cranial

Caudal

tpos

uwitan

uh

cisht

tleng

twi

L R

The resulting values were summed to arrive at total fat and protein yields up to May 12.Average percentage of milk fat and protein was calculated by dividing total fat or protein yieldsby total commercial milk yield. Somatic cell counts were transformed to base-10 logarithms andaveraged for each ewe. Days in milk were the number of days post-partum between May 12 andthe lambing date. Average daily commercial milk yield for each ewe was calculated by dividingthe total commercial milk yield by the number of days in milk.

Regression coefficients for the udder measurements were generated using the GLMprocedure of SAS (1999) with the following model:

Y = par + ebrd + nutr + wg + ls + dim + ucirc + uwid + uleng + uht + cisht + tang + tleng + twid+ tpos + error.

The dependent variables, Y, in the models were:

y512: test-day commercial milk yield on May 12time: average of all milking times recorded for a ewe (a.m. and p.m.)avgdyld: average daily commercial milk yieldtyldkg: total commercial milk yieldfatavg: average percentage of milk fatfatkg: total fat yieldproavg: average percentage of milk proteinprokg: total protein yieldlogavg: average log somatic cell count

Main effects accounted for in the models included:

par: parity (2nd, 3rd, or 4th)ebrd: breed of ewe (≤ _ EF, > _ to < _ EF, or > _ EF)nutr: nutrition (pasture or drylot)wg: weaning group (DY1 or MIX, see McKusick et al., 1999)ls: litter size (1, 2, or ≥ 3)

Regressors (covariates) in the models were:

dim: number of days in milk cisht: cistern heightucirc: udder circumference tang: teat angleuwid: udder width tleng: teat lengthuleng: udder length twid: teat widthuht: udder height tpos: teat position score

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Results and Discussion

Unadjusted ewe means and ranges for various lactation traits are presented in Table 3 tofamiliarize the reader with milk production of our EF crossbred dairy ewe flock at the time ofudder measuring. Ewes had been lactating for approximately 71 d, were producing about 2 L/d,and had already produced 141 kg of milk. Average milking time was 174 sec (almost 3 min perewe), which included machine stripping. Average percentages of milk fat and protein were 5.07and 4.77%, respectively. Average somatic cell count was 4.75 log units (56, 234 cells/ml ofmilk).

Unadjusted ewe means and ranges for udder teat morphology traits measured are pre-sented in Table 4. Tables 1 and 2 summarize measurements made by other authors on Lacaune,Rouge de l’Ouest, Manchega, Churra, Sarda, and Chios dairy ewes. Although there are someinconsistencies with respect to stage of lactation and time of day when udders were measured,some general comparisons can be made between our EF crossbred flock and other dairy breeds.Udder circumference (46.2 cm) was similar to what has been reported for Churra and Chios dairyewes. Udder width and height (14.6 cm) were similar for our EF crossbred ewes, and these bothdiffer from what has been reported for other breeds. Our EF crossbred ewes had wider uddersthan Lacaune, Manchega, or Churra ewes (however the measurements for these later three breedswere either taken later in lactation or closer to the morning milking). When comparing udderheight measurements of the present experiment with those in the literature, it must be noted thatour measurements did not include the height of the cistern. However, when cistern height issubtracted from udder height for values reported in the literature, our EF crossbred ewes stillhave shorter udders than either Lacaune or Manchega ewes. Average udder length for our EFcrossbred ewes was 11.2 cm, which is longer than what has been reported for other breeds. EFcrossbred ewes in the present experiment had greater cistern height (2.97 cm) than all otherbreeds reported except the Sarda (3.19 cm). Average teat angle for our EF crossbred ewes was58.3°, which is more horizontal than all other reports except the Sarda (67.2°). This is to beexpected because teat angle increases as cistern height increases (Fernandez et al., 1995; Rovai etal., 1999). Compared to other breeds, teat length for our EF crossbred ewes (2.6 cm) tended tobe shorter, but teat width (1.64 cm) was similar. EF crossbred ewes in the present experimenthad cranially placed teats (score of 2.93), but were less cranial than other breeds.

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Table 3. Unadjusted ewe means (±stdev) and range for lactation traits

Mean (±stdev) Minimum MaximumTrait

Test-day yield, L 2.03±.72 .60 3.60

Milking time, sec 174±64 76 394

Days in milk, d 71.2±15 37.0 97.0

Total commercial milk yield , kg 141±55 32.3 281

Average daily commercial milk yield, L/d 2.03±.62 .69 3.42

Average milk fat, % 5.07±.86 3.10 7.05

Total fat yield, kg 7.29±3.2 1.50 14.4

Average milk protein, % 4.77±.32 3.98 5.76

Total protein yield, kg 6.72±2.6 1.59 13.4

Average somatic cell count,log units 4.75±.31 4.27 5.88

Table 4. Unadjusted ewe means (±stdev) and range for udder measurements

Mean (±stdev) Minimum MaximumMeasurement

Udder circumference, cm 46.2±5.3 35.0 61.0

Udder width, cm 14.6±2.0 9.50 19.0

Udder length, cm 11.2±2.0 6.50 16.0

Udder height, cm 14.6±2.2 8.00 21.0

Cistern height, cm 2.97±1.5 .30 8.50

Teat angle, deg 58.3±12 31.5 89.0

Teat length, cm 2.60±.49 1.50 4.25

Teat width, cm 1.64±.28 1.00 2.75

Teat position score, no 2.93±.64 1.50 5.00

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Regression coefficients for udder and teat measurements on lactation traits are summa-rized in Table 5 and are bold-faced when significant ( P < .10). Udder circumference and udderheight (udder volume) have been previously shown to be significantly correlated with milk yield(Labussière et al., 1981; Labussière, 1988; Mavrogenis et al., 1988; Charon, 1990). In thepresent experiment, it is estimated that for each centimeter increase in udder circumference andudder height, there is a relative increase of .06 and .11, respectively, in liters of daily commercialmilk yield. Milking procedure time is highly correlated with commercial milk yield, uddervolume (Labussière et al., 1981), and quite possibly cistern height, as more time is needed formachine stripping. Our results support these relationships found in other studies, and predict thatfor each centimeter increase in udder length, udder height, and cistern height, there is a relativeincrease of 9.4, 4.8, and 15.1 seconds, respectively, in milking time. Correlations of udder andteat measurements with milk composition and quality traits are not readily available in theliterature. Our work suggests that there is a significant relationship between cistern height andaverage percentage of milk fat. For each centimeter increase in cistern height there is a relativeincrease of .12 in percentage units of milk fat. This would imply that ewes with deeper cisternsare able to store milk and milk fat in the cistern between milkings, and avoid the deleteriouseffects of residual milk on the secretory alveoli of the udder (Labussière et al., 1978; Wilde et al.,1987, 1995). Although in the present experiment the regression coefficients for teat width ontest-day yield and average daily yield were non-significant, it has been previously shown thatteat width tends to increase with milk yield (Fernandez et al., 1995). Therefore, the significantlynegative regression coefficients between teat width and percentage of milk fat and milk proteincould be explained by the dilution effect: as milk yield increases, percentage of milk fat andprotein decrease. The significant regression coefficients between average log somatic cell countand udder morphology traits are not easily explained. It would be expected for traits that arepositively correlated with milk yield, that somatic cell count should increase accordingly. How-ever, udder length is the only trait with a positive regression coefficient with somatic cell count.

Acknowledgments

The authors wish to thank Lori Brekenridge and Ann Stellrecht. Without their invaluableassistance with the collection of data, this experiment would not have been possible.

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Literature Cited

Carta, A., S. R. Sanna, G. Ruda, and S. Casu. 1999. Genetic aspects of udder morphology inSarda primiparous ewes. In: Milking and milk production of dairy sheep and goats. EAAPPubl. No. 95. Wageningen Pers, Wageningen, The Netherlands.

Charon, K. M. 1990. Genetic parameters of the morphological traits of sheep udder. WorldRev. of Anim. Prod. XXV(1):73-76.

de la Fuente, L. F., G. Fernández, and F. San Primitivo. 1996. A linear evaluation system forudder traits of dairy ewes. Live. Prod. Sci. 45:171-178.

de la Fuente, L. F., Pérez-Guzmán, M. H. Othmane, and J. Arranz. 1999. Améliorationgénétique de la morphologie de la mamelle dans les races Churra, Laxta, and Manchega. In:Milking and milk production of dairy sheep and goats. EAAP Publ. No. 95. WageningenPers, Wageningen, The Netherlands.

Fernández, G., P. Alvarez, F. San Primitivo, and L. F. de la Fuente. 1995. Factors affectingvariation of udder traits in dairy ewes. J. Dairy Sci. 78:842-849.

Fernández, G., J. A. Baro, L. F. de la Fuente, and F. San Primitivo. 1997. Genetic parameters forlinear udder traits of dairy ewes. J. Dairy Sci. 80:601-605.

Gootwine, E., B. Alef., and S. Gadeesh. 1980. Udder conformation and its heritability in theAssaf (Awassi x East Friesian) cross of dairy sheep in Israel. Ann. Génét. Sél. Anim.12(1):9-13.

Labussière, J., J. F. Combaud, and P. Pétrequin. 1978. Influence respective de la fréquencequotidienne des évacuations mammaires et des stimulations du pis sur l’entretien de lasécrétion lactée chez la brebis. Ann. Zootech. 27(2):127-137.

Labussière, J., D. Dotchewski, and J. F. Combaud. 1981. Caractéristiques mophologiques de lamammelle des brebis Lacaune. Méthodologie pour l’obtention des données. Relations avecl’aptitude à la traite. Ann. Zootech. 30(2):115-136.

Labussière, J. 1983. Etude des aptitudes laitières et de la facilité de traite de quelques races debrebis du Bassin Méditerranéen. Projet M4 FAO. In: 3ème Symposium Internacional deOrdeño Mecanico de Pequeños Rumiantes. Edit. Sever, Valladolid, Espagne. pp. 730-803.

Labussière, J. 1988. Review of physiological and anatomical factors influencing the milkingability of ewes and the organization of milking. Live. Prod. Sci. 18:253-273.

Malher, X. and F. Vrayla-Anesti. 1994. An evaluation of milk yield and milking ability inFrench Rouge de l’Ouest ewes. Sm. Rum. Res. 13:1-8.

Marie, C., M. Jacquin, M. R. Aurel, F. Pailler, D. Porte, P. Autran, and F. Barillet. 1999.Déterminisme génétique de la cinétique d’émission du lait selon le potentiel laitier en raceovine de Lacaune et relations phénotypiques avec la morphologie de la mamelle. In: Milk-ing and milk production of dairy sheep and goats. EAAP Publ. No. 95. Wageningen Pers,Wageningen, The Netherlands.

Mavrogenis, A. P., C. Papaachristoforou, P. Lysandrides, and A. Roushias. 1988. Environmentaland genetic factors affecting udder characters and milk production in Chios sheep. Génét.Sél. Evol. 20(4):477-488.

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McKusick, B. C., Y. M. Berger, and D. L. Thomas. 1999. Weaning and rearing systems forAmerican dairy sheep. J. Anim. Sci. 77(Suppl. 1):238.

Rovai, M., X. Such, J. Piedrafita, G. Caja, and M. R. Pujol. 1999. Evolution of mammarymorphology traits during lactation and its relationship with milk yield of Manchega andLacaune dairy sheep. In: Milking and milk production of dairy sheep and goats. EAAPPubl. No. 95. Wageningen Pers, Wageningen, The Netherlands.

Such, X., G. Caja, and L. Pérez. 1999. Comparison of milking ability between Manchega andLacaune dairy ewes. In: Milking and milk production of dairy sheep and goats. EAAPPubl. No. 95. Wageningen Pers, Wageningen, The Netherlands.

SAS. 1999. SAS User’s Guide (Release 7.0). SAS Inst. Inc., Cary, NC.Thomas, D. L. 1996. Opportunities for genetic improvement of dairy sheep in North America.

Proc. of the Second Great Lakes Dairy Sheep Symposium, March 28, Madison, WI, USA.47-51.

Wilde , C. J., D. T. Calvert, A. Daly, and M. Peaker. 1987. The effect of goat milk fractions onsynthesis of milk constituents by rabbit mammary explants and on milk yield in vivo.Biochem. J. 242:285-288.

Wilde, C. J., C. V. P. Addey, L. M. Boddy, and M. Peaker. 1995. Autocrine regulation of milksecretion by a protein in milk. Biochem. J. 305:51-58.

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INTROGRESSION OF THE FecB ALLELE OF THE BOOROOLA MERINO INTO ARAMBOUILLET FLOCK - A PROGRESS REPORT

A.E. Crooks, D.L. Thomas, R.D. Zelinsky, R.G. Gottfredson, B.C. McKusickDepartment of Animal Sciences and Arlington Agricultural Research Station


Objectives

1) Determine the effect of the FecB allele of the Booroola Merino in a U.S. sheep flockunconfounded by background genotype, and 2) develop a flock of high percentage Rambouilletsheep with the FecB allele.

Procedure

A project to introgress the FecB into a Rambouillet flock was initiated at the DixonSprings Agricultural Center of the University of Illinois in 1985, and the project was moved tothe Arlington Agricultural Research Stations of the University of Wisconsin-Madison in 1991.This report presents results obtained during the 1997 breeding and 1998 lambing season.

Rambouillet (Fec++) and Booroola Merino (FecBB) rams were initially mated to a flock ofRambouillet ewes during the autumns of 1985 through 1988. Booroola Merino-Rambouilletcross female progeny from this mating and subsequent matings were backcrossed to Rambouilletrams, and Rambouillet ewes continued to be mated to Rambouillet rams. The same Rambouilletrams were mated with the Rambouillet and Booroola Merino-cross ewes. Lambs were weaned atapproximately 60 days of age. Rambouillet replacement ewes and rams were selected on esti-mated genetic merit for litter size using the “Number of Lambs Born” FEPD from NSIP. Ram-bouillet/Booroola Merino-cross (RB) replacement ewes had to be an F1 or have a dam that hadbeen classified as a carrier (FecB+). Selection preference was given to ewe lambs with higherpercentages of Rambouillet breeding. Ewes were mated in order to lamb first at approximately 2years of age and annually thereafter. Prior to breeding each year, ovulation rate of ewes wasdetermined by counting number of corpora lutea viewed with a laparascope. RB ewes wereclassified as carriers (FecB+) if they had 3 or more ovulations at their first examination at approxi-mately 19 months of age and non-carriers if they had 1 or 2 ovulations. After their first orsecond lambing, the Fec++ RB ewes generally were culled to make room for RB replacementsfrom dams classified as FecB+. Approximately 60 Rambouillet and 60 RB ewes were mated eachyear.

In 1998, the majority of the RB ewes were of 7/8 or 15/16 Rambouillet breeding. Giventhe replacement policy used, the average age of the ewe groups differed and ranked from oldestto youngest, was Rambouillet, RB FecB+, and RB Fec++.

Results

Performance of the breed groups in the 1997/1998 production year is reported in Table 1.No significant difference was found between the three groups for ewe productivity (kg of lambweaned per ewe exposed). The RB FecB+ ewe group did have a significantly higher prolificacyand ovulation rate (P < .05) than the other two Fec++ groups. The significant difference of prolifi-cacy was nullified by non-significant decreases in lamb survival and weaning weight.

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Results found are similar to past years where the increase in prolificacy of carriers of the FecB

allele was negated by reduced lamb survival and weaning weight. The cause of decreased sur-vival and weaning weight could be due to various factors. Management techniques have beenimproved in handling the increased prolificacy, but the management system may be too demand-ing for ewes to handle more than 2 lambs efficiently.

Table 1. Least squares means (±SE) of lamb growth and reproductive performance of Rambouillet† ewes

Ewe breeding and genotype

Trait Rambouillet, Fec++ RB, Fec++ RB, FecB+

Ewes mated, no. 61 13 47

Ovulation rate, no. 1.89±.13a 1.75±.19a 3.44±.14b

Fertility, % 86.0±4.4 84.9±.10.7 91.8±4.9

Prolificacy, no. 1.72±.09a 1.72±.22a 2.18±.10b

Lamb survival, % 94.9±3.3 91.1±6.3 87.5±3.0

Lamb weaning weight, kg 17.48±.56 16.59±1.09 16.38±.51

Ewe productivity, kg 23.81±1.49 21.51±3.63 26.11±1.62

† Rambouillet (Fec++) , RB (Fec++), and RB (FecB+) ewesa,b Within a column and of an independent factor, means lacking a common superscript letter are different (P < .05).

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1998-99 REPRODUCTIVE PERFORMANCE OF THE SPOONERAGRICULTURAL RESEARCH STATION FLOCK

Yves BergerSpooner Agricultural Research Station


Table 1. 1999 Reproductive Performance of ewe lambs1 bred to East Friesian rams2.

Breed

1/2 EF 3/4 EF Dorset Type

Number of ewes at breeding 77 11 14Number of ewes at lambing 77 11 14Number of ewes aborted 10 2 0Number of ewes lambed 65 8 14Number of lambs born 120 18 22Number of lambs dead before weaning3 30 7 0

Birth weight of males 8.9 8.5 11.0Birth weight of females 8.3 9.1 9.230 day weight of males4 27.6 28.5 33.630 day weight of females4 26.8 25.4 28.9

Fertility 97.4% 90.9% 100.0%Litter size 1.83 2.25 1.57Survival rate 75.0% 61.2% 100.0%

Total 30 day weight/ewe 38.6 26.5 49.4

1. Ewe lambs born between February and April 1998.2. Natural mating between October 20 & November 30 and from December 1 through January 6.3. Including all lambs born alive or dead.4. Weaning of all lambs at 30 days of age.

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Table 2. Reproductive performance of artificially1 inseminated commercial ewes2 with eitherEast Friesian or Lacaune semen.

Sire Breed

East Friesian Lacaune

Number of ewes at breeding 22 22Number of ewes at lambing 22 21Number of ewes aborted 0 0Number of ewes lambed 16 17Number of lambs born 41 48Number of lambs dead before weaning3 5 5

Birth weight of males 10.2 8.7Birth weight of females 9.3 7.860 day weight of males4 52.6 51.960 day weight of females4 50.7 47.0

Fertility 72.0% 77.0%Litter size 2.56 2.82Survival rate 88.0% 90.0%

Total 60 day weight/ewe 116. 4 125.2

1. AI performed on November 19, 1998.2. 1/2 Dorset, 1/4 Romanov, 1/4 Targhee or 1/2 Dorset, 1/4 Finn, 1/4 Targhee.3. Including all lambs born dead or alive.4. All lambs weaned at 60 days.

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Table 3. Reproductive performance of mature dairy ewes artificially inseminated1 to eitherBritish or American Suffolk.

Breed of Ewes

1/4 EF 3/8 EF 1/2 EF2 Other

Number of ewes at breeding 74 41 52 9Number of ewes at lambing 72 41 52 9Number of ewes aborted 7 3 5 0Number of ewes lambed 60 40 45 8Number of lambs born 131 84 96 13Number of lambs dead before weaning3 22 18 13 1

Birth weight of males 11.7 11.2 12.1 10.9Birth weight of females 10.9 10.6 10.2 11.330 day weight of males4 32.9 31.0 30.5 27.330 day weight of females4 29.1 29.5 26.7 28.6

Fertility5 83.0% 105.0% 98.0% 88.0%Litter size 2.18 2.10 2.13 1.62Survival rate 83.2% 78.6% 86.5% 92.4%

Total 30 day weight/ewe 47.0 48.7 48.9 37.8

1. Ewes AI’d on 9/18, 9/24, 10/8, 10/14. Clean up mating with live Suffolk at the followingcycle.

2. Some ewes were more than 1/2 East Friesian.3. Including all lambs born dead or alive and even aborted fetuses.4. All lambs weaned at 30 days. Half of all lambs were raised on milk replacer.5. Fertility might be over 100% since all aborted ewes were exposed to rams on March 1, 1999.

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Documents

Table of Contents Program 2 Acknowledgements 4 What Have ... copy/sheep... · Yves Berger 63 Past Recipients of the Sheep Industry Award 66 Index 67 3. ... Madison (Michel Wattiaux,