Interpreting ReproductiveEfficiency Indexes

Dr. M.A. Varner, Dr. J.L. Majeskie,and S.C. GarlichsUniversity of Maryland

IntroductionReproductive efficiency is the ability of a dairyproducer to get cows bred back rapidly aftercalving with a minimum number of breedings percow. Inefficient reproduction decreases profit byreducing both the efficiency of milk productionand the number of available replacement heifers.Also, there may be increased breeding costs andveterinary fees. Breeding records, summarized as areproductive efficiency index, provide the bestindication of breeding problems. More importantly,indexes can give clues as to what the cause ofproblems might be.

Reproductive efficiency indexes are also useful todairy producers who currently do not haveproblems getting cows pregnant. Trends in theseindexes can be used to detect problems as theydevelop. Steps to correct the problem can be takenbefore the problem becomes more serious.

The index values for a herd should not becompared only to guidelines contained in this factsheet, but also to index values for the state and/orcounty in which the herd is located. The guidelinesare goals for optimal efficiency. Regionaldifferences, such as weather, may make goalsmore difficult to reach for some producers.Consequently, comparing state and county indexvalues to herd values can provide an indication ofhow good a job a particular producer is doingwhen compared to neighbors. State and/or countyvalues can usually be obtained from CooperativeExtension Service state specialists or countyagents.

IRM-5

Dairy IntegratedReproductiveManagement

The breeding records necessary for calculation ofthe indexes discussed in this fact sheet are:

1. Date (month, day, and year) of the most recentcalving

2. Date of the previous calving for second andlater lactation cows

3. Reproductive status (pregnant, open, and bredbut too early to detect pregnancy)

4. Number of breedings for all cows, and

5. Date(s) of first breeding and most recentbreeding if a cow has been bred more thanonce.

Indexes ofReproductive EfficiencyDays Open

Days Open measures overall reproductiveperformance for the previous 12 months. Problemswith fertility (Fact Sheet IRM-10) and/or estrousdetection (Fact Sheet IRM-6) increase Days Open.Projected Minimum Calving Interval is calculatedby adding Days Open to the gestation length for anormal cow. It is interpreted in a manner similar toDays Open.

A small portion of cows with high Days Openusually inflates the herd’s average Days Open to asmall degree. If Days Open is inflated significantlyby a few problem breeding cows, these cowsshould be culled. The culling policy forreproductive problems in the herd should beexamined. Fact Sheet IRM-17 can provide a basisfor understanding the costs of keeping problembreeders in the herd too long.

Current Days Open when added to a gestationlength for a normal cow will not always be equalto the Calving Interval one to two years from now.Some cows with reproductive problems are culledand never contribute to the Calving Interval. Thisdifference is usually small, unless a significantportion of the herd is culled for reproductiveproblems.

If most of the cull cows are removed from the herdfor reproductive problems, then current Days Openplus gestation length may be larger than futureCalving Interval. Of course, a serious problemexists in any herd where most of the cull cows areremoved for reproductive problems. The causes ofthese problems should be determined byexamining the indexes of reproductive efficiencyas described in this IRM fact sheet.

To calculate Days Open for a herd, list for eachcow the number of days from calving to:

1. Conception for pregnant cow2. Last breeding for cows which are bred but not

yet confirmed pregnant, or3. Current date for open cows. Do not include

cows that will be culled due to reproductiveproblems, but are still in the herd because ofhigh milk production.

Calculate the average Days Open for the herd byadding together the Days Open for each cow anddivide the total by the number of cows in the herd.

A guideline for interpreting Days Open issummarized in Table 1. A herd average of 85 daysor less for Days Open indicates cows are beingbred too early in lactation. Recent research hasshown that the level of milk production wasdecreased significantly in the lactation thatfollowed early postpartum (after calving)breedings.

Most producers are interested in overall efficiencyof milk production (commercial herds) and not inobtaining large milk production records on specificcows. Some breeders of registered cattle, however,are interested in obtaining maximal milkproduction records on individual cows to increasethe sale value of these animals or their offspring.

Days Open values between 116 and 145 Days areinterpreted differently for these two types of herds.A value for Days Open of 116 to 130 Days indicatesa slight problem for commercial herds, but may beadequate for breeders of registered cattle. A valuefor Days Open of 131 to 145 Days indicates amoderate problem for commercial herds and aslight problem for registered herds. A value forDays Open of over 145 Days indicates a severeproblem for all herds.

Table 1. A List of Various Levels for DaysOpen and a Short Interpretation forEach Level

Level of Days Open1 Interpretation

Under 85 Days Too LO W

85 to 115 Days Optimum For Most Herds

116 to 130 Days Slight Problem for MostHerds

131 to 145 Days Moderate to Slight Problem

Over 145 Days Severe Problem

1Herds with a seasonal calving pattern should use the highestvalue for Days Open during the last 12 months.

Actual Calving IntervalActual Calving Interval is an indication ofreproductive performance from 9 months to 2years prior to the current date. This measure onlyreflects reproductive successes, however, anddoes not take into account reproductive failures.Cows that are culled for reproductive problemscan be considered failures.

Actual Calving Interval is figured by calculatingthe number of months between the most recentcalving and the previous calving for each cow insecond or later lactation. A Calving Interval is notcalculated for first-calf heifers. The CalvingInterval for each cow is then added together andthe total is divided by the number of cows insecond or later lactation.

Actual Calving Interval should be interpretedaccording to the guidelines in Table 2. Producerswith a herd having an Actual Calving Interval ofunder 11.7 months and a Days Open of under 85Days should breed cows later in lactation for theirfirst service to increase Days Open to 85-115 Days.Recent research indicates that milk production ofherds with an Actual Calving Interval of under 11.7months is significantly less than milk productionof herds with a Calving Interval of 11.8-13.0months.

Similar to Days Open, Calving Intervals forcommercial herds are interpreted differently thanCalving Intervals for herds with registered cattle.An Actual Calving Interval of 13-13.5 monthsshould be considered a slight to moderate problemfor commercial but may be adequate for registeredherds. An Actual Calving Interval of 13.6 to 14.0months is considered a moderate problem forcommercial herds and a slight to moderateproblem for registered herds. An Actual CalvingInterval of over 14.0 months is indicative of asevere problem in all herds.

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Table 2. A List of Actual Calving Intervalsand a Brief Interpretation for EachInterval.

Calving Interval(Months) Interpretation

Under 11.7 Too LOW

11.8 -13.0 Optimum for Most Herds13.0 -13.5 Slight Problem for Most

Herds13.6 -14.0 Moderate to Slight ProblemOver 14.0 Severe Problem

Days in Milk atFirst Service (DFS)

The average DFS for a herd is influenced by amanagement decision of when first breeding willoccur postpartum. This earliest number of daysdecided upon by management (DFS Goal) variesgreatly between herds. Some cows can be safelybred as early as 40 days postpartum; however,highest fertility levels usually are not reached until60 days. Many producers breed cows at their firstestrus after 45 days postpartum. These producersavoid many fertility problems by having theirveterinarian palpate all cows prior to 45 dayspostpartum to diagnose reproductive problemssuch as severe uterine infections (metritis; FactSheet IRM-22). Breeding of cows with metritis canthen be delayed until the uterine infection iseliminated and the uterus is healthy. The averageDFS for a herd is influenced by when the ovariesof a cow begin to function again postpartum andthe number of unobserved estrous periods.

The average DFS for a herd is figured as follows:

1. Calculate the number of days from calvinguntil first service for all cows inseminated.

2. Calculate the average DFS for the herd byadding together the DFS for each cow anddividing the total by the number of cowsinseminated.

After determining the earliest number of dayspostpartum that a cow can be bred in a herd (DFSGoal), the average DFS for a herd should beinterpreted according to the guidelines in Table 3.Problems in herds with average DFS minus DFSGoal over 18 days can be due to cows beinganestrus and/or unobserved estrous periods. Amethod for determining the cause of the problemis described in Fact Sheet IRM-7.

Table 3. The Relationship of Average Daysto First Service (DFS) and DFS Goal toReproductive Efficiency.

Average DFS MinusDFS Goal Interpretation

Under 18 Days No Problem19 to 26 Days Moderate Problem1

Over 26 Days Severe Problem1

1The cause of the problem may be due to cows being anestrusand/or to estrous periods being missed.

Services PerConception (S/Conc)

Average S/Conc for a herd is a measure of fertilityin cows which were reproductive successes andhave become pregnant. Breedings for cull cowsand repeat breeder cows (Fact Sheet IRM-23) notdiagnosed pregnant are not included in this index.

Average S/Conc can be figured as follows:

1. Count the total number of breedings (thislactation) for each pregnant cow,

2. Add the numbers together,

3. Calculate the average S/Conc by dividing thetotal number of breedings by the number ofpregnant cows.

Average S/Cone should be interpreted according tothe guidelines in Table 4. Poor levels of fertilitymay be due to inaccurate estrous detection (FactSheet IRM-6). Accurate estrous detection may beconfirmed by milk progesterone analysis (FactSheet IRM-9). Improper techniques for artificialinsemination (Fact Sheet IRM-12) may also lead toS/Conc greater than 2.0. An examination oftechniques used in artificial insemination or arefresher course could be beneficial.

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Table 4. The Relationship BetweenServices Per Conception (S/Conc) andLevel of Fertility.

S/Conc Fertility Level

Under 1.75 Good level1.76-2.00 Adequate Level2.01-2.30 Moderate ProblemOver 2.30 Severe Problem

Interpreting Indexes ofReproductive EfficiencyCompare Actual Calving Interval toProjected MinimumCalving Interval (Days Open)

This comparison can indicate whether overallreproductive efficiency during the last nine monthsis better, the same, or worse than the herdreproductive efficiency during the previous year.To compare Days Open to Actual Calving Interval(Cl), a Projected Minimum Calving Interval (PMCI)is calculated. Average Days Open is added to thegestation length, in days, for the most commonbreed in a herd (Ayrshire, 278 days; Brown Swiss,290 days; Guernsey, 284 days; Holstein, 279 days;and Jersey, 279 days). This total is then divided by30.25 days/month. For example, PMCI for aHolstein herd averaging 123 Days Open would becalculated:

123 days + 279 days= 13.3 months for PMCI.30.25 days/month

Comparisons of Cl and PMCI should be interpretedaccording to the guidelines in Table 5. Herdreproductive management does not need to bechanged with improving reproductive efficiency,unless the number of missed estrous periods orrepeat breeders still requires improvement. Forherds with an unchanging level of reproductiveefficiency, the effectiveness of reproductivemanagement procedures should be evaluated ifthe value for Days Open indicates a problemexists. If overall reproductive efficiency has gottenworse during the last nine months, theeffectiveness of management proceduresconcerning reproduction should be evaluated.

Table 5. The Relationship of ActualCalving Interval (Cl) and ProjectedMinimum Calving Interval (PMCI) to Levelof Reproductive Efficiency.

Comparison of Cl Level ofand PMCI Reproductive Efficiency

Cl Greater than PMCI ImprovingCl Similar to PMCI Staying SameCl Less the PMCI Growing Worse

Calculate EstrousDetection Efficiency

Estrous detection efficiency can be expressed asthe percentage of Heats Detected (total estrousperiods when a cow was detected in estrus).The percentage of Heats Detected can be estimatedby first calculating an average breeding interval forthe herd and then comparing the breeding intervalto Table 6. Breeding interval is the average numberof days between first breeding and theinsemination resulting in pregnancy. Averagebreeding interval, can be calculated by thefollowing formula:

Breeding Interval = Average Days Open-DFS(S/Cone-l)

An example for a herd with an average Days Openof 140, an average DFS of 2.6 would be:

Breeding Interval = 140-75=41 days(2.6-1)

Comparing the breeding interval to Table 6, 41days corresponds to 50% of Heats Detected.

A guideline for interpreting percentage of HeatsDetected is summarized in Table 7. Producers withsevere problems should improve their estrousdetection program (Fact Sheet IRM-6). Moderateproblems may be caused by not observing estrusin certain cows. Examining records of individualcows may be useful. Anestrous cows or cows withfeet and leg problems may be difficult to observein estrus.

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Table 6. An Estimation of Percentage ofHeats Detected Based on Breeding Interval.

BreedingInterval (Days) % Heats Detected

23 9026 8030 7035 6041 5050 4060 30

Source: Grusenmeyer, D., et al., Evaluating Dairy Herd Repro-ductive Status Using DHI Records. WashingtonState University, Western Regional Extension Publication,WREP 0067, 1983.

Table 7. The Relationship of PercentageHeats Detected to Estrous DetectionEfficiency.

Percent Heats Level of EstrousDetected Detection Efficiency

Under 50% Severe Problem50-65% Moderate Problem66-80% Adequate EfficiencyOver 80% Excellent Efficiency’

Trade or brand names are mentioned only for information.The Cooperative Extension Service intends no endorsement norimplies discrimination to the exclusion of other products whichalso may be suitable.

1Herds that also have a poor level of fertility (S/Conc over 2.0)should use milk progesterone analysis to determine theaccuracy of heats detected.

Some herds may have excellent estrous detectionefficiency yet have poor fertility (S/Conc over 2.0),suggesting a problem in estrous detectionaccuracy. (Cows are thought to be in estrus whenthey are not.) Progesterone analysis of milksamples collected on the day of breeding can beused to determine accuracy of estrous detection(Fact Sheet IRM-9).

SummaryInefficient reproduction is costly and can becaused by different problems. Records,summarized into indexes of reproductiveefficiency, are valuable tools because they can beused to identify causes of breeding problems.Indexes can also be used to spot developingproblems before they become more serious.Profits can be increased significantly by mostproducers if breeding problems are solved.

Programs and activities offered by the West Virginia University Extension Service are available to all persons without regard to race, color,sex, disability, religion, age, veteran status, sexual orientation or national origin.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department ofAgriculture. Director, Cooperative Extension Service, West Virginia University.

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