Equine Reproduction and Genetics Equine Science 2

Equine Reproduction and Genetics

Equine Science 2

A. Heat Detection is Key to A. Heat Detection is Key to any Breedingany Breeding

1.1. The ability to determine when the The ability to determine when the mare is ready to be bred is important mare is ready to be bred is important for the success of any equine for the success of any equine reproduction management system.reproduction management system.a.a. Conception rates are highest when mares Conception rates are highest when mares

are bred 1 -2 days before ovulation.are bred 1 -2 days before ovulation.

b.b. Therefore, the best time to breed occurs Therefore, the best time to breed occurs 24 to 48 hours before the end of estrus. 24 to 48 hours before the end of estrus.

B. Key to Detecting Estrus B. Key to Detecting Estrus

1.1. The key signal of estrus is the receptivity The key signal of estrus is the receptivity of the mare to a stallion.of the mare to a stallion.

a.a. To determine if a mare is in heat and is To determine if a mare is in heat and is receptive to a stallion, one can tease a mare receptive to a stallion, one can tease a mare with a stallion to observe specific behaviors.with a stallion to observe specific behaviors.

b.b. A handler, or some form of barrier, partition, A handler, or some form of barrier, partition, or restraint is used to ensure the mare and or restraint is used to ensure the mare and stallion remain separated while behaviors are stallion remain separated while behaviors are observed.observed.

B. Key to Detecting EstrusB. Key to Detecting Estrus

2.2. Keep accurate records for each Keep accurate records for each mare for each teasing secession or mare for each teasing secession or teasing program will not be teasing program will not be effective.effective.

a.a. A numbered scoring system is often A numbered scoring system is often used, where 0=the mare rejects the used, where 0=the mare rejects the stallion and 4= the mare shows stallion and 4= the mare shows intense interest in the stallion.intense interest in the stallion.

C. Ways of Teasing a Mare to C. Ways of Teasing a Mare to Detect EstrusDetect Estrus1.1. Group teasing is used when a large Group teasing is used when a large

number of mares need to be observed.number of mares need to be observed.a.a. A stallion is placed in a central pen A stallion is placed in a central pen

surrounded by connected and adjoining surrounded by connected and adjoining pens where several mare can be placed pens where several mare can be placed to allow the equine limited contact.to allow the equine limited contact.1)1) Sometimes called a teasing mill.Sometimes called a teasing mill.

2)2) required a minimum amount of handling.required a minimum amount of handling.

C. Ways of Teasing a Mare to C. Ways of Teasing a Mare to Detect EstrusDetect Estrus

a)a) Disadvantages is the shy mares may not Disadvantages is the shy mares may not approach the stallion to exhibit behaviors and approach the stallion to exhibit behaviors and dominant mares may hinder shy mares.dominant mares may hinder shy mares.

b.b. Mares must be given a minimum of 15 -Mares must be given a minimum of 15 -20 minutes to show signs.20 minutes to show signs.

2.2. Individual teasing is used when one Individual teasing is used when one mare is teased by the teasing stallion.mare is teased by the teasing stallion.

a.a. A teasing rail is used to keep a single A teasing rail is used to keep a single mare and stallion apart while behavior is mare and stallion apart while behavior is observed observed

C. Ways of Teasing a Mare to C. Ways of Teasing a Mare to Detect EstrusDetect Estrus

b.b. The teasing rail should be a solid The teasing rail should be a solid partition of about 4’ high to avoid partition of about 4’ high to avoid injury to the mare or stallion.injury to the mare or stallion.

D.D. Behaviors exhibited by a Behaviors exhibited by a mare in standing heat:mare in standing heat:

1.1. Flexing the pelvis.Flexing the pelvis.2.2. Raising her tail.Raising her tail.3.3. Frequent urination.Frequent urination.4.4. Spreading her hind legs.Spreading her hind legs.5.5. Contracting and relaxing the vulva.Contracting and relaxing the vulva.6.6. Allowing the stallion to nip and chew on her Allowing the stallion to nip and chew on her

flanks and neck.flanks and neck.7.7. A mare the shows intense interest will practice A mare the shows intense interest will practice

winking, where she raises her tail, urinates, and winking, where she raises her tail, urinates, and exposes the clitoris as she assumes the mating exposes the clitoris as she assumes the mating position.position.

E. Reasons for Manipulating E. Reasons for Manipulating EstrusEstrus1.1. Mares are seasonally polyestrous, that is, Mares are seasonally polyestrous, that is,

a) the go into heat several times a year, a) the go into heat several times a year, but b) they usually go into heat during but b) they usually go into heat during specific seasons of the year.specific seasons of the year.

2.2. Most mares do not cycle naturally in the Most mares do not cycle naturally in the winter.winter.

a.a. Spring-type conditions of increased daylight, Spring-type conditions of increased daylight, warmer temperatures and improved nutrition warmer temperatures and improved nutrition from better quality of forage have a indirect from better quality of forage have a indirect affect on the pituitary gland. affect on the pituitary gland.

E. Reasons for Manipulating E. Reasons for Manipulating EstrusEstrus

a.a. The result is that the pituitary gland secretes The result is that the pituitary gland secretes FSH (Follicle Stimulating Hormone) and LH FSH (Follicle Stimulating Hormone) and LH (Lutenizing Hormone) which are essential for (Lutenizing Hormone) which are essential for the estrus cycle.the estrus cycle.

3.3. The two major reasons for The two major reasons for rearranging the heat cycles of the rearranging the heat cycles of the mare are:mare are:

a.a. For the convenience of the owner for For the convenience of the owner for showing and racing.showing and racing.

b.b. Higher reproductive efficiency.Higher reproductive efficiency.


4.4. Race and show equine ages are based on Race and show equine ages are based on the calendar year. Therefore, they need the calendar year. Therefore, they need to be bred earlier than the natural to be bred earlier than the natural breeding period for equine.breeding period for equine.

a.a. The common birthday for race and show The common birthday for race and show horses is considered January 1horses is considered January 1stst..

b.b. Foals born closer to January 1Foals born closer to January 1stst will be older will be older relative to foals born later in the year and relative to foals born later in the year and should have an advantage over other should have an advantage over other individuals in their age division.individuals in their age division.


c.c. Rather than breeding in March or April Rather than breeding in March or April as usual, these animals need to be as usual, these animals need to be bred in early February.bred in early February.

F. Two most common techniques F. Two most common techniques used to manipulate estrusused to manipulate estrus

1.1. Environmental stimulation is the simplest Environmental stimulation is the simplest and most effective technique used. and most effective technique used.

a.a. Extending day length to 16 hours of light with Extending day length to 16 hours of light with artificial lights has worked best.artificial lights has worked best.

b.b. A 200-watt incandescent bulb or 2 40-watt A 200-watt incandescent bulb or 2 40-watt florescent bulbs hung at a height from 7’ to florescent bulbs hung at a height from 7’ to 8’ provides adequate light in the average 8’ provides adequate light in the average stall.stall.

c.c. Artificial light increases shedding.Artificial light increases shedding.d.d. Increased heat and improved nutrition are Increased heat and improved nutrition are

part of the increased lighting program.part of the increased lighting program.

F. Two most common techniques F. Two most common techniques used to manipulate estrus.used to manipulate estrus.

b.b. Three hormones have been used in Three hormones have been used in conjunction to manipulate estrus:conjunction to manipulate estrus:1)1) Prostaglandin is the Prostaglandin is the most widely used most widely used and has been and has been

used to induce estrus and control the lifespan of the used to induce estrus and control the lifespan of the corpus luteum. (mares must be cycling to work)corpus luteum. (mares must be cycling to work)

2)2) HCG (Human Chorionic Gondotropin) is the most HCG (Human Chorionic Gondotropin) is the most common gondotropin hormone and has been used common gondotropin hormone and has been used to control ovulation.to control ovulation.

3)3) Progesterone and synthetic progestin such as Progesterone and synthetic progestin such as “Regumate” are steroid hormones that keep mares “Regumate” are steroid hormones that keep mares out of estrus.out of estrus.

F. Two most common techniques F. Two most common techniques used to manipulate estrus.used to manipulate estrus.

2.2. Chemical hormone control has been Chemical hormone control has been used to stimulate cycling and used to stimulate cycling and control ovulation.control ovulation.

a.a. Chemical control requires the Chemical control requires the synchronization of ovulation and estrus synchronization of ovulation and estrus and works best when used along with and works best when used along with rectal palpation and reproductive rectal palpation and reproductive ultrasonography.ultrasonography.

A. Care of the mare.A. Care of the mare.

1.1. Classifications of mares affect the kind of Classifications of mares affect the kind of management decisions.management decisions.

a.a. Maiden mares have never been bred nor had a Maiden mares have never been bred nor had a foal. A maiden mare may be frightened or reject foal. A maiden mare may be frightened or reject her foal when it tries to nurse.her foal when it tries to nurse.1)1) Rubbing some of her milk on the foal helps her Rubbing some of her milk on the foal helps her

identify the foal as hers.identify the foal as hers.2)2) Avoid touching the foal, the mare and foal Avoid touching the foal, the mare and foal

identifies one another by smell, the dam and identifies one another by smell, the dam and the foal must bond or the foal may become the foal must bond or the foal may become attached to humans.attached to humans.

A. Care of the mare. A. Care of the mare.

b.b. A barren mare is one that A barren mare is one that is not pregnant, but was is not pregnant, but was bred in the previous or bred in the previous or current season.current season.

1)1) Indicates there was a failure Indicates there was a failure in conception or in in conception or in maintaining pregnancy.maintaining pregnancy.


c.c. An open mare is An open mare is one that was not one that was not pregnant and not pregnant and not bred in the bred in the previous or current previous or current season.season.

d.d. Pregnant mare will Pregnant mare will foal in the current or foal in the current or following seasonfollowing season


2)2) Management involves discovering if there is a Management involves discovering if there is a problem and correction it.problem and correction it.

3)3) Uterine infections are a major cause of infertility Uterine infections are a major cause of infertility and is most often caused by pnuemovagina, and is most often caused by pnuemovagina, (windsucking), as a result of poor breeding (windsucking), as a result of poor breeding conformation.conformation.

4)4) Age and poor nutrition may also contribute to Age and poor nutrition may also contribute to breeding problems.breeding problems.


e.e. Wet mares are nursing a foal and need a Wet mares are nursing a foal and need a ration to supply energy and protein for ration to supply energy and protein for lactation.lactation.1)1) Energy needed increases by about 45%, but is Energy needed increases by about 45%, but is

helped if the mare is in proper body condition.helped if the mare is in proper body condition.

2)2) Protein needed for lactation increases by Protein needed for lactation increases by almost 65% and is often more limited.almost 65% and is often more limited.

A. Care for the mare.A. Care for the mare.

2.2. Importance's of proper Importance's of proper body conditionbody condition

a.a. Body condition scoring Body condition scoring is an excellent is an excellent management tool.management tool.

1)1) Numbers 1-9 are used Numbers 1-9 are used to indicate the amount to indicate the amount of body fat on an of body fat on an equine with higher equine with higher scores meaning the scores meaning the animal is carrying more animal is carrying more body fat.body fat.


2)2) Mares should score Mares should score between a 5.5 and between a 5.5 and 7.5 on body 7.5 on body condition; some fat is condition; some fat is deposited along the deposited along the withers, behind the withers, behind the shoulders, around shoulders, around the tail head and ribs the tail head and ribs cannot be scene but cannot be scene but felt with some fat in felt with some fat in between.between.

A. Care for the mare. A. Care for the mare.

b.b. The second The second trimester is the best trimester is the best time to help a mare time to help a mare get in the correct get in the correct body condition if body condition if she is not already she is not already there.there.

1)1) Feed .4 to .6 pounds Feed .4 to .6 pounds of grain per 100 of grain per 100 pounds of body pounds of body weight and weight and supplement with hay supplement with hay if pasture is poor.if pasture is poor.


3.3. Pregnancy checking is important for all bred Pregnancy checking is important for all bred mares in the fall to ensure mare have mares in the fall to ensure mare have maintained pregnancy, even though they were maintained pregnancy, even though they were checked in the spring breeding season. checked in the spring breeding season. Pregnancy checking can be accomplished by:Pregnancy checking can be accomplished by:

a.a. Palpation or using one hands to feel the form, size, Palpation or using one hands to feel the form, size, position and consistency of the uterus. (usually done position and consistency of the uterus. (usually done by veterinarians and trained horse people)by veterinarians and trained horse people)


1)1) A mare must be 28 to 30 days into gestation A mare must be 28 to 30 days into gestation (pregnancy) before palpation can be used to (pregnancy) before palpation can be used to diagnose pregnancy.diagnose pregnancy.

2)2) Is one of the quickest and most efficient Is one of the quickest and most efficient methods of diagnosing pregnancy.methods of diagnosing pregnancy.


b.b. Ultrasonography uses an ultrasound probe Ultrasonography uses an ultrasound probe inserted into the equine’s rectum and inserted into the equine’s rectum and moved across the reproductive tract to moved across the reproductive tract to produce sound waves the either reflect produce sound waves the either reflect from or propagate through various tissue from or propagate through various tissue materials to produce an image that materials to produce an image that determines and monitors pregnancy.determines and monitors pregnancy.1)1) Ultrasonography is very accurate, can diagnose Ultrasonography is very accurate, can diagnose

pregnancy as early as 14 days, and is very pregnancy as early as 14 days, and is very useful in determining the length of pregnancy.useful in determining the length of pregnancy.


2)2) Ultrasonography can determine the sex of the Ultrasonography can determine the sex of the animal between 60 to 70 days of the gestation animal between 60 to 70 days of the gestation period.period.

3)3) . Ultrasound can diagnose reproductive . Ultrasound can diagnose reproductive problems in nonpregnant maresproblems in nonpregnant mares


c.c. Blood test to determine changes in Blood test to determine changes in hormone level can give an indication of the hormone level can give an indication of the stage of pregnancy.stage of pregnancy.1)1) The presence and levels of ECG (Equine The presence and levels of ECG (Equine

Chorionic Gonadotrophin) in the mares blood Chorionic Gonadotrophin) in the mares blood between 40 and 130 days of gestation indicate between 40 and 130 days of gestation indicate the mare has “settled” and high levels of the mare has “settled” and high levels of estrogen sulfate (a form of estrogen) indicate a estrogen sulfate (a form of estrogen) indicate a live embryo or fetus.live embryo or fetus.


4.4. Feeding management means meeting the Feeding management means meeting the mare’s maintenance requirements for the first mare’s maintenance requirements for the first 8 months of gestation. 8 months of gestation. If the mare is in If the mare is in correct body condition.correct body condition.

a.a. It is important to say consistent, that is do not let It is important to say consistent, that is do not let her loose or gain weight.her loose or gain weight.

b.b. She probably will not need grain if pasture is She probably will not need grain if pasture is adequate, but should have ample clean, fresh adequate, but should have ample clean, fresh water and trace mineralized salt provided free water and trace mineralized salt provided free choice.choice.


5.5. Health care includes dental, Health care includes dental, hoof, deworming, and hoof, deworming, and scheduled vaccinations.scheduled vaccinations.

a.a. Do no give unnecessary drugs Do no give unnecessary drugs during the first 60 days and the last during the first 60 days and the last 30 days of pregnancy.30 days of pregnancy.

b.b. Vaccinations are common for Vaccinations are common for rinopneumonitis, influenza, tetanus, rinopneumonitis, influenza, tetanus, equine encephalomyelitis.equine encephalomyelitis.


6.6. Preparing for foalingPreparing for foalinga.a. While broodmares do not need shoes, if they are While broodmares do not need shoes, if they are

shod, shoes need to be removed prior to foaling to shod, shoes need to be removed prior to foaling to protect the foal at birth.protect the foal at birth.

b.b. The mare should be moved where she is going to The mare should be moved where she is going to foal 30 days prior to foaling so that she may foal 30 days prior to foaling so that she may produce protective antibodies for the environment produce protective antibodies for the environment to be included in colostrum.to be included in colostrum.

1)1) The foal has to obtain antibodies against infection from The foal has to obtain antibodies against infection from colostrum.colostrum.


2)2) Foal’s intestines will absorb antibodies only Foal’s intestines will absorb antibodies only during the first 24 hours after birth.during the first 24 hours after birth.

c.c. The best prediction of foaling time is past The best prediction of foaling time is past foaling history and knowledge of gestation foaling history and knowledge of gestation lengths.lengths.1)1) Normal gestation period is 342 days plus or Normal gestation period is 342 days plus or

minus 20 days.minus 20 days.2)2) Signs will vary but may include signs of Signs will vary but may include signs of

restlessness and sweating.restlessness and sweating.3)3) Wax beads (drops of colostrum) appear on the Wax beads (drops of colostrum) appear on the

teats 3-4 days prior to foaling.teats 3-4 days prior to foaling.


7.7. Foaling should occur in a clean place where Foaling should occur in a clean place where the mare and foal can bond without the mare and foal can bond without unnecessary interruptions. If in a small unnecessary interruptions. If in a small paddock, no other horses should be around.paddock, no other horses should be around.

a.a. In a normal birth presentation, the foal’s front feet In a normal birth presentation, the foal’s front feet (one slightly in front of the other) appear first with (one slightly in front of the other) appear first with the heals down toward the mare’s hock. The foal’s the heals down toward the mare’s hock. The foal’s nose should be lying on or about the knees.nose should be lying on or about the knees.


b.b. If foaling is in a stall, the preferred bedding is If foaling is in a stall, the preferred bedding is wheat, rye, or barley straw since shavings and wheat, rye, or barley straw since shavings and sawdust cling to afterbirth and may lead to sawdust cling to afterbirth and may lead to infections.infections.

c.c. In the absence of dystocia (difficult foaling) due In the absence of dystocia (difficult foaling) due to abnormal presentation position, twinning, or to abnormal presentation position, twinning, or other birthing problems, the foal and mare other birthing problems, the foal and mare should be monitored but allowed to bond should be monitored but allowed to bond without human contact.without human contact.


d.d. Foaling occurs in three stages:Foaling occurs in three stages:1)1) Mare may be restless a few minutes to 24 Mare may be restless a few minutes to 24

hours prior to her water breaking.hours prior to her water breaking.2)2) Hard labor should last from 20 to 30 minutes, if Hard labor should last from 20 to 30 minutes, if

the foal’s front feet and head are not seen the foal’s front feet and head are not seen within 5 to 10 minutes of the onset of hard within 5 to 10 minutes of the onset of hard labor, the mare should be gotten up and walked labor, the mare should be gotten up and walked until a veterinarian arrives.until a veterinarian arrives.

3)3) The uterus shrinks and the placenta (afterbirth) The uterus shrinks and the placenta (afterbirth) is expelled within 2 to 3 hrs of birth or a medical is expelled within 2 to 3 hrs of birth or a medical emergency exist that requires a veterinarians emergency exist that requires a veterinarians assistance.assistance.


8.8. Post foaling management includes:Post foaling management includes:a.a. Close monitoring for the first 48 to 72 hours.Close monitoring for the first 48 to 72 hours.b.b. Allowing the foal and mare out in the paddock for Allowing the foal and mare out in the paddock for

exercise the day after birth, weather permitting, to exercise the day after birth, weather permitting, to assist the mare in uterine discharge and return to assist the mare in uterine discharge and return to normal.normal.

c.c. Looking for signs of a swollen, feverish, udder that Looking for signs of a swollen, feverish, udder that indicate the foal is not nursing.indicate the foal is not nursing.

d.d. Providing the mare with slightly warm water, some Providing the mare with slightly warm water, some form of wet-bran mash, and alfalfa hay to give a form of wet-bran mash, and alfalfa hay to give a slightly laxative affect to assist and comfort her in slightly laxative affect to assist and comfort her in defecating.defecating.


9.9. Foal heat occurs 3-12 days after foaling and Foal heat occurs 3-12 days after foaling and sometimes an attempt is made to breed sometimes an attempt is made to breed mares during this short estrus cycle.mares during this short estrus cycle.

a.a. Conception rate is only 40% and increased risks Conception rate is only 40% and increased risks are present.are present.

b.b. The advantage is that the next years foaling date The advantage is that the next years foaling date is moved up when the mare successfully carries a is moved up when the mare successfully carries a foal consummated during foal heat.foal consummated during foal heat.

B. Care of the stallion.B. Care of the stallion.

1.1. The number of The number of mares a stallion will mares a stallion will settle (breed settle (breed successfully) successfully) depends largely on depends largely on the age of the the age of the stallion and the stallion and the mating system mating system used.used.

B. Care of the stallion.B. Care of the stallion.Age of stallionAge of stallion Average number of Average number of

mares settled when mares settled when hand mated is usedhand mated is used

Average number of Average number of mares settled when mares settled when pasture mating is usedpasture mating is used

Two year old Two year old 1010 55

Three year oldThree year old 3030 1515

Mature Mature stallionsstallions

5050 2525

YEARLINGS SHOULD NOT BE DEPENDED ON YEARLINGS SHOULD NOT BE DEPENDED ON FOR BREEDING PROGRAMFOR BREEDING PROGRAM


b.b. Breeding stallions should Breeding stallions should be fed like an equine at be fed like an equine at hard workhard work

1)1) Approximately 1.5 Approximately 1.5 pounds of grain and 1 pounds of grain and 1 pound of hay per 100 pound of hay per 100 pounds of body weight.pounds of body weight.

2)2) Grazing good grass, if Grazing good grass, if only for short time only for short time periods, is periods, is recommendedrecommended


c.c. Fencing should be Fencing should be tall and strong tall and strong particularly when particularly when mares are in mares are in adjoining pastures, adjoining pastures, unless pasture unless pasture mating is on a ready mating is on a ready serve basis.serve basis.

d.d. Regular exercise Regular exercise usually results in usually results in increased sexual increased sexual vigor and fertility.vigor and fertility.

A. Newborn foal care.

1. First, make sure the foal is breathing properly by cleaning the mucous out of its nostrils. This can be done by carefully placing the thumb and forefinger along the top of the nostrils towards the muzzle.

2. Make sure there are no objects in the foals mouth that might choke it.


3. If the umbilical cord does not break in birthing and there is no danger to the foal, wait 10 to 15 minutes after birth to break it.

a. The extra time allows about 30% of the foals blood to flow from the mare.

b. NEVER cut the umbilical cord, because a clean cut causes excessive bleeding.


c. Procedures for breaking the umbilical cord:

1) Find the narrowing of the umbilical cord located about 2 inches from the foals abdomen.

2) Place the cord over the first and second fingers with narrow area between them.

3) Press down with thumb until cord breaks.

4) NEVER pull against the foals abdomen.


4. The naval stump needs to be treated soon after birth with a 2% iodine or 50-50 mixture of 7% iodine and glycerine to prevent infection and neonatal septicemia.

a. The glycerine causes the iodine to stick to the naval stump.

b. Apply iodine 2 to 3 times a day during the first day at 6 to 8 hour intervals.


5. If the mare has not had a tetanus immunization before foaling, give the foal a tetanus antitoxin injection.

A. New born foal care.

6. The foal must nurse within 2 to 3 hours after birth, and the foal must obtain an adequate amount of colostrum during its first 12 hours of life to supply antibodies.

a. There is no placental transfer of antibodies from the mare to the foal during pregnancy,

b. Foals rely on passive transfer of immunity from colostrum to protect them from disease.


7. Many newborn foals are constipated and should be treated with a 4-ounce Fleet phosphate enema available from drug stores.

B. Foal observation.

1. Observe the foal especially during the first 48 to 72 hours after birth.

a. A normal foal should be active when awake.

b. A healthy foal will normally sleep on their side.

B. Foal observation

2. Foals should nurse as often as seven times a hour during their first week, and gradually decline to where they only nurse once per hour by seven weeks of age.

a. A mare with a full, hot, or leaking udder is an indication the foal has not nursed and a sure sign that the foal is sick.

b. A foal that is nursing, but not gaining weight may not be getting adequate milk as a result of the mare’s eating endophyte-infected fescue pasture

C. Weaning

1. Weaning normally occurs at 4 to 6 months and is a stressful time for the foal and dam.

a. Reduce stress by separating with a fence that allows the dam and foal to see, smell, and hear each other.

b. Separation for increased lengths of time also works well to prevent stress. The foal may nurse 3 times the first day, 2 times the second day, once in the third day, and completely separated the fourth day.

C. Weaning

2. Foals who are eating creep feed suffer less at weaning. Creep feed for foals must contain 16-18 percent protein, 0.8 percent calcium, and 0.55 percent phosphorus. The calorie to protein ratio should be 55-50 grams of protein per Mcal.

C. Weaning

3. Delay worming, vaccinations and halter training until 3-4 weeks after training.

A. Pasture Mating is the Least A. Pasture Mating is the Least Managed System of BreedingManaged System of Breeding

1.1. Mares and stallions Mares and stallions are allowed in the are allowed in the same pasture. same pasture.

2.2. Stallions breed any Stallions breed any mare in heat.mare in heat.

B. Hand matingB. Hand mating Hand mating is a system of breeding where a handler Hand mating is a system of breeding where a handler

restrains the mare to prevent injury to the stallion while restrains the mare to prevent injury to the stallion while allowing the stallion to pursue the breeding process.allowing the stallion to pursue the breeding process.

1.1. Most expensive horses are hand mated.Most expensive horses are hand mated.

2.2. Mares that are selected for hand mating are Mares that are selected for hand mating are supposed to be in heat.supposed to be in heat.

C. Artificial InseminationC. Artificial Insemination Artificial Insemination (A.I) is a system of breeding Artificial Insemination (A.I) is a system of breeding

where semen is collected from a stallion is where semen is collected from a stallion is deposited into the uterus of a mare without deposited into the uterus of a mare without copulation.copulation.

1.1. Semen is collected in an artificial vagina from a Semen is collected in an artificial vagina from a stallion that mounts a mare or phantom mare.stallion that mounts a mare or phantom mare.

2.2. A catheter is placed into the uterus of the mare in A catheter is placed into the uterus of the mare in heat and a syringe is used to transfer the collected heat and a syringe is used to transfer the collected semen through the catheter.semen through the catheter.

D. Embryo TransferD. Embryo Transfer

Embryo Transfer is the non-surgical removal Embryo Transfer is the non-surgical removal of an embryo from the uterus of one mare of an embryo from the uterus of one mare and inserting it into the uterus of another and inserting it into the uterus of another mare.mare.

1.1. The recipient mare contributes nothing to the The recipient mare contributes nothing to the genetics of the foal.genetics of the foal.

D. Embryo TransferD. Embryo Transfer

2.2. Consists of three phases:Consists of three phases:1)1) Synchronization of the donor and recipient mares so that Synchronization of the donor and recipient mares so that

ovulation occurs in both within a 12 hour time period is ovulation occurs in both within a 12 hour time period is done with hormone therapydone with hormone therapy

2)2) Flushing the embryo in a sterile solution 7 to 8 days after Flushing the embryo in a sterile solution 7 to 8 days after insemination insemination

3)3) Transferring the embryo in a nurturing solution through a Transferring the embryo in a nurturing solution through a uterine transfer catheter ( an extra recipient mare is uterine transfer catheter ( an extra recipient mare is usually used to insure use of the best synchronization.usually used to insure use of the best synchronization.

A. Pasture mating

1. Advantages of pasture mating:a. Pasture mating is convenient to the

equine owner because very little labor and management are required.

b. Pasture mating catches mares shy about breeding.

c. Pasture mating results in a high “settle percentage” ( a high conception rate among mares that are bred)

A. Pasture Mating

2. Disadvantages of pasture mating:a. A lower number of mares can be

serviced by the stallion.b. Breeding dates are hard to

determine.c. There is some risk to injury to the

stallion in pasture mating. (Stallions shown for conformation cannot safely be pasture mated)

B. Hand Mating

1. Advantages of hand matinga. Hand mating prevents injury to the

stallion during the breeding process.b. Breeding sanitation is preformed by

the handler which protects both the mare and the stallion.

B. Hand Mating

2. Disadvantages of hand mating:a. The settling percentage is not as

high as pasture mating.b. Hand mating requires additional

labor to have a handler present during the breeding process.

C. Artificial Insemination (A.I)1. Advantages of artificial

inseminationa. Venereal disease control is possible by

diluting collected semen with antibodies prior to depositing in the mare.

b. Chances of injury to handler and equine are less than with other mating systems.

c. Overuse of the stallion is less likely since one collection of semen may be enough to breed several mares.

C. Artificial Insemination (A.I)

d. Semen is evaluated for quality at periodic intervals during the use of A.I.

2. Disadvantages of Artificial Insemination

a. A higher number of mares fail to settle or conceive than with pasture mating.

b. A.I. requires trained personnel to collect and deposit semen at the appropriate time for conception.

c. A.I. is labor intensive.

D. Embryo Transfer

1. Advantages of Embryo Transfera. Increased production of foals from

genetically superior mares.b. Reproduction from older, less fertile

mares that are great mares.c. Reproduction by 2-yr old mares.d. Allows a valuable sport donor mare

to reproduce without incurring term of pregnancy.

D. Embryo Transfer

2. Disadvantages of Embryo Transfer

a. Very expensive.b. Yield is low.

A. Genetics

The study of heredity and variation.

A. Genetics

1. Heredity- is the resemblance among individuals that is passed on, or capable of being passed on, genetically from parents to offspring.

a. Genes are the basic unit of inheritance and are passed to the next generation in gamete (sex cell) formation on chromosomes.

A. Genetics

b. Different forms of the same gene at the same location on the chromosome are called alleles.

c. Genes are made of DNA (deoxyribonucleic acid) in specific sequence (DNA sequence) that gives an organism its own unique traits.

d. Genes are carried on chromosomes and must occur in distinct pairs for normal body growth and development.

A. Genetics

e. Chromosomes also occur in distinct pairs and are consistent in number for a species of horse having 64 chromosomes (32 distinct pairs) and donkeys having 62 chromosomes or 31 distinct pairs to make up their genome (complete set of chromosomes)

A. Genetics

2. Variation is the occurrence of differences among individuals of the same species due to genetic variation.

a. Chromosomes and gene numbers change during gamete (sex cell) formation:

1) First, the 32 chromosome pairs of a cell duplicate, then one of the four members associated with the duplicated pairs is randomly transferred to one of the four forming gametes.

A. Genetics

2) The random transfer of chromosomes and their genes to forming gametes is the major cause of genetic differences among related individuals.

3) The newly formed gamete now contains only one member of each original chromosome pair.

4) When egg and sperm unite at fertilization, the chromosome number is restored to its original value.

A. Genetics

b. The new cell formed is the zygote that develops into a fetus.

1) The zygote has one member of each chromosome pair from its sire and the other member from its dam.

2) The resulting offspring is genetically different from either parent, but carries genetic traits of both.

B. Genetics and traits

1. The genetic make-up (specific genes that reside in the gene pairs which control a trait) is the animal’s genotype.

a. Each cell contains a duplicate set of genes derived from the single gene sets received at conception by both the mother and father.


b. The duplicate genes (alleles) are similar but not necessarily identical. For example, while both sets of genes are for hair structure, one set may be for straight hair and the other be curly hair.


2. Both sets of genes function simultaneously in the cell. If the pair has identical genes, it is a homozygous gene pair. If the gene pair has different genes, the gene pair is a heterozygous gene pair.


a. If the gene pair is heterozygous, one allele may be dominant and the other recessive. Dominant does not mean better, but that the allele is expressed when placed in relationship with the recessive allele.

1) the dominant allele of a gene is expressed with a capital letter such as A,B,C,D…..W,X,Y,Z

2) The recessive allele of a gene is expressed as a lower case letter such as a,b,c,d,…w,x,y,z.


b. Very few economically important traits are controlled by one or few gene pairs, but rather possibly hundreds of gene pairs.


3. There are two categories of traits:a. Qualitative traits are:

1) Controlled by one or very few gene pairs that can be easily identified

2) Little impacted by the environment

3) Easily broken into distinct categories that look the same.


b. Quantitative traits are controlled by hundreds or thousands of gene pairs.

1) The environment does affect the expression of the gene pairs controlling quantitative traits.

2) Most economically important traits are quantitative traits.

3) Phenotypes of quantitative traits are not able to be classified into distinct categories.


4. Regardless of whether the traits are quantitative or qualitative, the individual’s phenotype (what we can see) is the sum of effects of the genotypic and the environmental effects.

B. Genetics and traits5. Influence of Genetics and Environment on Certain Traits in

Equine Trait Due to Genetics-

%Due to Environment-%

Height at Withers 40 to 50 50 to 55

Body Weight 25 to 30 70 to 75

Body Length 30 to 40 60 to 65

Heart Girth Circumference 20 to 25 75 to 80

Pulling Power 20 to 30 70 to 80

Walking Speed 40 to 45 55 to 60

Movement 40 to 50 50 to 60

Temperament 25 to 30 70 to 75

Reproductive Traits 10 to 15 85 to 90

A. Genetics and Sex Determination

1. Chromosomes determine the sex of an equine.a. Females carry XX chromosomes and every egg

possesses one X chromosome.

b. Males carry XY chromosomes and half the sperm carry the X chromosome and the other half carries the Y chromosome.

2. When the eggs and sperm unite, half the zygotes will be female (XX) and the other half will be male (XY).

B. Genetics and Color

1. Genetic determination of coat color is based on the presence of alleles or different forms of each gene that determines coat color.


a. Dominant alleles are represented by a capital letter. They are never hidden by their related recessive alleles.

1. When present, W (white) or G (grey) gene alleles will hide other coat-color genes.

2. You cannot determine by looking at an animal if the second allele is dominant or recessive.


b. Recessive alleles are represented by a lower case letter. Hidden recessive genes are hidden by a dominant allele.

1) Recessive genes can only by expressed if both of the pair are the same. For example, recessive genes such as ww will always be expressed as nonwhite, gg will always be nongrey.


2. Coat Color Classification Based on the Effects of the Alleles of Seven Genes (see handout)

C. Mules and Hinnies

1. Mules are a genetic abnormality in that they have an uneven number of chromosomes. (63 chromosomes)

a. Sire is a male donkey (jack) which has 62 chromosomes (31 pairs).

b. Dam is a female horse (mare) which has 64 chromosomes (32 pairs).

c. The mule has the features of a horse in size and body shape, but has a shorter, thicker head with long ears and the braying voice of a donkey.

d. Mules are usually infertile.

C. Mules and Hinnies

2. The hinny or jennet is the reverse cross between a stallion and a female donkey.

a. Similar to the mule in appearance, but smaller and more horse like, with shorter ears and a longer head

b. Hinnies are more difficult to produce than mules, and rarely will a female mule or hinny come into heat and produce a foal.

A. Steps in defining coat color

1. Determine if G or W alleles are present. If they are present, the process stops. They mask other colors.

2. If neither G or W alleles are present, look for black hair either on the points or distributed over the body. If yes, then the EE or Ee allele is present. If the hair is red, then the ee allele is present.

B. Genetic Formulas and Resulting Coat Colors

Genetic Formula Color

W White

G Gray

E, A, CC, dd, gg, ww, toto Bay

E, aa, CC, dd, gg, ww, toto Black

ee, aa, CC, dd, gg, ww, toto Red

E, A, CCer, dd, gg, ww, toto Buckskin

ee, CCer, dd, gg, ww, toto Palomino

CerCer Cremello

E, A, CC, dd, gg, ww, TO Bay Tobiano

ee, CC, D, gg, ww, TO Red Dun Tobiano

Documents

Equine Reproduction and Genetics Equine Science 2