Equine Reproduction and Genetics

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Equine Reproduction and Genetics

• Equine Science 2

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A. Heat Detection is Key to any Breeding

• The ability to determine when the mare is ready
  to be bred is important for the success of any
  equine reproduction management system.
• Conception rates are highest when mares are bred
  1 -2 days before ovulation.
• Therefore, the best time to breed occurs 24 to 48
  hours before the end of estrus.

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B. Key to Detecting Estrus

• The key signal of estrus is the receptivity of
  the mare to a stallion.
• To determine if a mare is in heat and is
  receptive to a stallion, one can tease a mare
  with a stallion to observe specific behaviors.
• A handler, or some form of barrier, partition, or
  restraint is used to ensure the mare and stallion
  remain separated while behaviors are observed.

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B. Key to Detecting Estrus

• Keep accurate records for each mare for each
  teasing secession or teasing program will not be
  effective.
• A numbered scoring system is often used, where
  0the mare rejects the stallion and 4 the mare
  shows intense interest in the stallion.

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C. Ways of Teasing a Mare to Detect Estrus

• Group teasing is used when a large number of
  mares need to be observed.
• A stallion is placed in a central pen surrounded
  by connected and adjoining pens where several
  mare can be placed to allow the equine limited
  contact.
• Sometimes called a teasing mill.
• required a minimum amount of handling.

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C. Ways of Teasing a Mare to Detect Estrus

• Disadvantages is the shy mares may not approach
  the stallion to exhibit behaviors and dominant
  mares may hinder shy mares.
• Mares must be given a minimum of 15 -20 minutes
  to show signs.
• Individual teasing is used when one mare is
  teased by the teasing stallion.
• A teasing rail is used to keep a single mare and
  stallion apart while behavior is observed

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C. Ways of Teasing a Mare to Detect Estrus

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

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Behaviors exhibited by a mare in standing heat

1. Flexing the pelvis.
2. Raising her tail.
3. Frequent urination.
4. Spreading her hind legs.
5. Contracting and relaxing the vulva.
6. Allowing the stallion to nip and chew on her
   flanks and neck.
7. A mare the shows intense interest will practice
   winking, where she raises her tail, urinates, and
   exposes the clitoris as she assumes the mating
   position.

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E. Reasons for Manipulating Estrus

• Mares are seasonally polyestrous, that is, a) the
  go into heat several times a year, but b) they
  usually go into heat during specific seasons of
  the year.
• Most mares do not cycle naturally in the winter.
• Spring-type conditions of increased daylight,
  warmer temperatures and improved nutrition from
  better quality of forage have a indirect affect
  on the pituitary gland.

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E. Reasons for Manipulating Estrus

• The result is that the pituitary gland secretes
  FSH (Follicle Stimulating Hormone) and LH
  (Lutenizing Hormone) which are essential for the
  estrus cycle.
• The two major reasons for rearranging the heat
  cycles of the mare are
• For the convenience of the owner for showing and
  racing.
• Higher reproductive efficiency.

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E. Reasons for Manipulating Estrus

• Race and show equine ages are based on the
  calendar year. Therefore, they need to be bred
  earlier than the natural breeding period for
  equine.
• The common birthday for race and show horses is
  considered January 1st.
• Foals born closer to January 1st will be older
  relative to foals born later in the year and
  should have an advantage over other individuals
  in their age division.

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E. Reasons for Manipulating Estrus

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

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F. Two most common techniques used to manipulate
estrus

• Environmental stimulation is the simplest and
  most effective technique used.
• Extending day length to 16 hours of light with
  artificial lights has worked best.
• A 200-watt incandescent bulb or 2 40-watt
  florescent bulbs hung at a height from 7 to 8
  provides adequate light in the average stall.
• Artificial light increases shedding.
• Increased heat and improved nutrition are part of
  the increased lighting program.

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F. Two most common techniques used to manipulate
estrus.

• Three hormones have been used in conjunction to
  manipulate estrus
• Prostaglandin is the most widely used and has
  been used to induce estrus and control the
  lifespan of the corpus luteum. (mares must be
  cycling to work)
• HCG (Human Chorionic Gondotropin) is the most
  common gondotropin hormone and has been used to
  control ovulation.
• Progesterone and synthetic progestin such as
  Regumate are steroid hormones that keep mares
  out of estrus.

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F. Two most common techniques used to manipulate
estrus.

• Chemical hormone control has been used to
  stimulate cycling and control ovulation.
• Chemical control requires the synchronization of
  ovulation and estrus and works best when used
  along with rectal palpation and reproductive
  ultrasonography.

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A. Care of the mare.

• Classifications of mares affect the kind of
  management decisions.
• Maiden mares have never been bred nor had a foal.
  A maiden mare may be frightened or reject her
  foal when it tries to nurse.
• Rubbing some of her milk on the foal helps her
  identify the foal as hers.
• Avoid touching the foal, the mare and foal
  identifies one another by smell, the dam and the
  foal must bond or the foal may become attached to
  humans.

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A. Care of the mare.

• A barren mare is one that is not pregnant, but
  was bred in the previous or current season.
• Indicates there was a failure in conception or in
  maintaining pregnancy.

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A. Care of the mare.

• An open mare is one that was not pregnant and not
  bred in the previous or current season.
• Pregnant mare will foal in the current or
  following season

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A. Care of the mare.

1. Management involves discovering if there is a
   problem and correction it.
2. Uterine infections are a major cause of
   infertility and is most often caused by
   pnuemovagina, (windsucking), as a result of poor
   breeding conformation.
3. Age and poor nutrition may also contribute to
   breeding problems.

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A. Care of the mare.

• Wet mares are nursing a foal and need a ration to
  supply energy and protein for lactation.
• Energy needed increases by about 45, but is
  helped if the mare is in proper body condition.
• Protein needed for lactation increases by almost
  65 and is often more limited.

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A. Care for the mare.

• Importance's of proper body condition
• Body condition scoring is an excellent management
  tool.
• Numbers 1-9 are used to indicate the amount of
  body fat on an equine with higher scores meaning
  the animal is carrying more body fat.

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A. Care for the mare.

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

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A. Care for the mare.

• The second trimester is the best time to help a
  mare get in the correct body condition if she is
  not already there.
• Feed .4 to .6 pounds of grain per 100 pounds of
  body weight and supplement with hay if pasture is
  poor.

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A. Care for the mare.

• Pregnancy checking is important for all bred
  mares in the fall to ensure mare have maintained
  pregnancy, even though they were checked in the
  spring breeding season. Pregnancy checking can be
  accomplished by
• Palpation or using one hands to feel the form,
  size, position and consistency of the uterus.
  (usually done by veterinarians and trained horse
  people)

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A. Care for the mare.

• A mare must be 28 to 30 days into gestation
  (pregnancy) before palpation can be used to
  diagnose pregnancy.
• Is one of the quickest and most efficient methods
  of diagnosing pregnancy.

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A. Care for the mare.

• Ultrasonography uses an ultrasound probe inserted
  into the equines rectum and moved across the
  reproductive tract to produce sound waves the
  either reflect from or propagate through various
  tissue materials to produce an image that
  determines and monitors pregnancy.
• Ultrasonography is very accurate, can diagnose
  pregnancy as early as 14 days, and is very useful
  in determining the length of pregnancy.

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A. Care for the mare.

• Ultrasonography can determine the sex of the
  animal between 60 to 70 days of the gestation
  period.
• . Ultrasound can diagnose reproductive problems
  in nonpregnant mares

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A. Care for the mare.

• Blood test to determine changes in hormone level
  can give an indication of the stage of pregnancy.
• The presence and levels of ECG (Equine Chorionic
  Gonadotrophin) in the mares blood between 40 and
  130 days of gestation indicate the mare has
  settled and high levels of estrogen sulfate (a
  form of estrogen) indicate a live embryo or
  fetus.

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A. Care for the mare.

• Feeding management means meeting the mares
  maintenance requirements for the first 8 months
  of gestation. If the mare is in correct body
  condition.
• It is important to say consistent, that is do not
  let her loose or gain weight.
• She probably will not need grain if pasture is
  adequate, but should have ample clean, fresh
  water and trace mineralized salt provided free
  choice.

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A. Care for the mare.

• Health care includes dental, hoof, deworming, and
  scheduled vaccinations.
• Do no give unnecessary drugs during the first 60
  days and the last 30 days of pregnancy.
• Vaccinations are common for rinopneumonitis,
  influenza, tetanus, equine encephalomyelitis.

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A. Care for the mare.

• Preparing for foaling
• While broodmares do not need shoes, if they are
  shod, shoes need to be removed prior to foaling
  to protect the foal at birth.
• The mare should be moved where she is going to
  foal 30 days prior to foaling so that she may
  produce protective antibodies for the environment
  to be included in colostrum.
• The foal has to obtain antibodies against
  infection from colostrum.

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A. Care for the mare.

• Foals intestines will absorb antibodies only
  during the first 24 hours after birth.
• The best prediction of foaling time is past
  foaling history and knowledge of gestation
  lengths.
• Normal gestation period is 342 days plus or minus
  20 days.
• Signs will vary but may include signs of
  restlessness and sweating.
• Wax beads (drops of colostrum) appear on the
  teats 3-4 days prior to foaling.

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A. Care for the mare.

• Foaling should occur in a clean place where the
  mare and foal can bond without unnecessary
  interruptions. If in a small paddock, no other
  horses should be around.
• In a normal birth presentation, the foals front
  feet (one slightly in front of the other) appear
  first with the heals down toward the mares hock.
  The foals nose should be lying on or about the
  knees.

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A. Care for the mare.

1. If foaling is in a stall, the preferred bedding
   is wheat, rye, or barley straw since shavings and
   sawdust cling to afterbirth and may lead to
   infections.
2. In the absence of dystocia (difficult foaling)
   due to abnormal presentation position, twinning,
   or other birthing problems, the foal and mare
   should be monitored but allowed to bond without
   human contact.

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A. Care for the mare.

• Foaling occurs in three stages
• Mare may be restless a few minutes to 24 hours
  prior to her water breaking.
• Hard labor should last from 20 to 30 minutes, if
  the foals front feet and head are not seen
  within 5 to 10 minutes of the onset of hard
  labor, the mare should be gotten up and walked
  until a veterinarian arrives.
• The uterus shrinks and the placenta (afterbirth)
  is expelled within 2 to 3 hrs of birth or a
  medical emergency exist that requires a
  veterinarians assistance.

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A. Care for the mare.

• Post foaling management includes
• Close monitoring for the first 48 to 72 hours.
• Allowing the foal and mare out in the paddock for
  exercise the day after birth, weather permitting,
  to assist the mare in uterine discharge and
  return to normal.
• Looking for signs of a swollen, feverish, udder
  that indicate the foal is not nursing.
• Providing the mare with slightly warm water, some
  form of wet-bran mash, and alfalfa hay to give a
  slightly laxative affect to assist and comfort
  her in defecating.

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A. Care for the mare.

• Foal heat occurs 3-12 days after foaling and
  sometimes an attempt is made to breed mares
  during this short estrus cycle.
• Conception rate is only 40 and increased risks
  are present.
• The advantage is that the next years foaling date
  is moved up when the mare successfully carries a
  foal consummated during foal heat.

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B. Care of the stallion.

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

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B. Care of the stallion.
Age of stallion Average number of mares settled when hand mated is used Average number of mares settled when pasture mating is used
Two year old 10 5
Three year old 30 15
Mature stallions 50 25
YEARLINGS SHOULD NOT BE DEPENDED ON FOR BREEDING PROGRAM
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B. Care of the stallion.

• Breeding stallions should be fed like an equine
  at hard work
• Approximately 1.5 pounds of grain and 1 pound of
  hay per 100 pounds of body weight.
• Grazing good grass, if only for short time
  periods, is recommended

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B. Care of the stallion.

• Fencing should be tall and strong particularly
  when mares are in adjoining pastures, unless
  pasture mating is on a ready serve basis.
• Regular exercise usually results in increased
  sexual vigor and fertility.

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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.

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A. Newborn foal care.

• 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.
• The extra time allows about 30 of the foals
  blood to flow from the mare.
• NEVER cut the umbilical cord, because a clean cut
  causes excessive bleeding.

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A. Newborn foal care.

• Procedures for breaking the umbilical cord
• Find the narrowing of the umbilical cord located
  about 2 inches from the foals abdomen.
• Place the cord over the first and second fingers
  with narrow area between them.
• Press down with thumb until cord breaks.
• NEVER pull against the foals abdomen.

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A. Newborn foal care.

• 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.
• The glycerine causes the iodine to stick to the
  naval stump.
• Apply iodine 2 to 3 times a day during the first
  day at 6 to 8 hour intervals.

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A. Newborn foal care.

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

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A. New born foal care.

• 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.
• There is no placental transfer of antibodies from
  the mare to the foal during pregnancy,
• Foals rely on passive transfer of immunity from
  colostrum to protect them from disease.

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A. Newborn foal care.

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

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B. Foal observation.

• Observe the foal especially during the first 48
  to 72 hours after birth.
• A normal foal should be active when awake.
• A healthy foal will normally sleep on their side.
  

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B. Foal observation

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

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C. Weaning

• Weaning normally occurs at 4 to 6 months and is a
  stressful time for the foal and dam.
• Reduce stress by separating with a fence that
  allows the dam and foal to see, smell, and hear
  each other.
• 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.

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C. Weaning

1. 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.

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C. Weaning

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

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A. Pasture Mating is the Least Managed System of
Breeding

1. Mares and stallions are allowed in the same
   pasture.
2. Stallions breed any mare in heat.

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B. Hand mating

• Hand mating is a system of breeding where a
  handler restrains the mare to prevent injury to
  the stallion while allowing the stallion to
  pursue the breeding process.
• Most expensive horses are hand mated.
• Mares that are selected for hand mating are
  supposed to be in heat.

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C. Artificial Insemination

• Artificial Insemination (A.I) is a system of
  breeding where semen is collected from a stallion
  is deposited into the uterus of a mare without
  copulation.
• Semen is collected in an artificial vagina from a
  stallion that mounts a mare or phantom mare.
• A catheter is placed into the uterus of the mare
  in heat and a syringe is used to transfer the
  collected semen through the catheter.

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D. Embryo Transfer

• Embryo Transfer is the non-surgical removal of an
  embryo from the uterus of one mare and inserting
  it into the uterus of another mare.
• The recipient mare contributes nothing to the
  genetics of the foal.

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D. Embryo Transfer

• Consists of three phases
• Synchronization of the donor and recipient mares
  so that ovulation occurs in both within a 12 hour
  time period is done with hormone therapy
• Flushing the embryo in a sterile solution 7 to 8
  days after insemination
• Transferring the embryo in a nurturing solution
  through a uterine transfer catheter ( an extra
  recipient mare is usually used to insure use of
  the best synchronization.

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A. Pasture mating

• Advantages of pasture mating
• Pasture mating is convenient to the equine owner
  because very little labor and management are
  required.
• Pasture mating catches mares shy about breeding.
• Pasture mating results in a high settle
  percentage ( a high conception rate among mares
  that are bred)

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A. Pasture Mating

• Disadvantages of pasture mating
• A lower number of mares can be serviced by the
  stallion.
• Breeding dates are hard to determine.
• There is some risk to injury to the stallion in
  pasture mating. (Stallions shown for conformation
  cannot safely be pasture mated)

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B. Hand Mating

• Advantages of hand mating
• Hand mating prevents injury to the stallion
  during the breeding process.
• Breeding sanitation is preformed by the handler
  which protects both the mare and the stallion.

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B. Hand Mating

• Disadvantages of hand mating
• The settling percentage is not as high as pasture
  mating.
• Hand mating requires additional labor to have a
  handler present during the breeding process.

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C. Artificial Insemination (A.I)

• Advantages of artificial insemination
• Venereal disease control is possible by diluting
  collected semen with antibodies prior to
  depositing in the mare.
• Chances of injury to handler and equine are less
  than with other mating systems.
• Overuse of the stallion is less likely since one
  collection of semen may be enough to breed
  several mares.

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C. Artificial Insemination (A.I)

• Semen is evaluated for quality at periodic
  intervals during the use of A.I.
• Disadvantages of Artificial Insemination
• A higher number of mares fail to settle or
  conceive than with pasture mating.
• A.I. requires trained personnel to collect and
  deposit semen at the appropriate time for
  conception.
• A.I. is labor intensive.

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D. Embryo Transfer

• Advantages of Embryo Transfer
• Increased production of foals from genetically
  superior mares.
• Reproduction from older, less fertile mares that
  are great mares.
• Reproduction by 2-yr old mares.
• Allows a valuable sport donor mare to reproduce
  without incurring term of pregnancy.

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D. Embryo Transfer

• Disadvantages of Embryo Transfer
• Very expensive.
• Yield is low.

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A. Genetics

• The study of heredity and variation.

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A. Genetics

• Heredity- is the resemblance among individuals
  that is passed on, or capable of being passed on,
  genetically from parents to offspring.
• Genes are the basic unit of inheritance and are
  passed to the next generation in gamete (sex
  cell) formation on chromosomes.

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A. Genetics

1. Different forms of the same gene at the same
   location on the chromosome are called alleles.
2. Genes are made of DNA (deoxyribonucleic acid) in
   specific sequence (DNA sequence) that gives an
   organism its own unique traits.
3. Genes are carried on chromosomes and must occur
   in distinct pairs for normal body growth and
   development.

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A. Genetics

1. 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)

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A. Genetics

• Variation is the occurrence of differences among
  individuals of the same species due to genetic
  variation.
• Chromosomes and gene numbers change during gamete
  (sex cell) formation
• 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.

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A. Genetics

1. The random transfer of chromosomes and their
   genes to forming gametes is the major cause of
   genetic differences among related individuals.
2. The newly formed gamete now contains only one
   member of each original chromosome pair.
3. When egg and sperm unite at fertilization, the
   chromosome number is restored to its original
   value.

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A. Genetics

• The new cell formed is the zygote that develops
  into a fetus.
• The zygote has one member of each chromosome pair
  from its sire and the other member from its dam.
• The resulting offspring is genetically different
  from either parent, but carries genetic traits of
  both.

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B. Genetics and traits

• The genetic make-up (specific genes that reside
  in the gene pairs which control a trait) is the
  animals genotype.
• Each cell contains a duplicate set of genes
  derived from the single gene sets received at
  conception by both the mother and father.

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B. Genetics and traits

1. 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.

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B. Genetics and traits

• 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.

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B. Genetics and traits

• 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.
• the dominant allele of a gene is expressed with a
  capital letter such as A,B,C,D..W,X,Y,Z
• The recessive allele of a gene is expressed as a
  lower case letter such as a,b,c,d,w,x,y,z.

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B. Genetics and traits

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

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B. Genetics and traits

• There are two categories of traits
• Qualitative traits are
• Controlled by one or very few gene pairs that can
  be easily identified
• Little impacted by the environment
• Easily broken into distinct categories that look
  the same.

80
B. Genetics and traits

• Quantitative traits are controlled by hundreds or
  thousands of gene pairs.
• The environment does affect the expression of the
  gene pairs controlling quantitative traits.
• Most economically important traits are
  quantitative traits.
• Phenotypes of quantitative traits are not able to
  be classified into distinct categories.

81
B. Genetics and traits

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

82
B. Genetics and traits

1. 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
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A. Genetics and Sex Determination

• Chromosomes determine the sex of an equine.
• Females carry XX chromosomes and every egg
  possesses one X chromosome.
• Males carry XY chromosomes and half the sperm
  carry the X chromosome and the other half carries
  the Y chromosome.
• When the eggs and sperm unite, half the zygotes
  will be female (XX) and the other half will be
  male (XY).

84
B. Genetics and Color

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

85
B. Genetics and Color

• Dominant alleles are represented by a capital
  letter. They are never hidden by their related
  recessive alleles.
• When present, W (white) or G (grey) gene alleles
  will hide other coat-color genes.
• You cannot determine by looking at an animal if
  the second allele is dominant or recessive.

86
B. Genetics and Color

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

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B. Genetics and Color

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

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C. Mules and Hinnies

• Mules are a genetic abnormality in that they have
  an uneven number of chromosomes. (63 chromosomes)
• Sire is a male donkey (jack) which has 62
  chromosomes (31 pairs).
• Dam is a female horse (mare) which has 64
  chromosomes (32 pairs).
• 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.
• Mules are usually infertile.

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C. Mules and Hinnies

• The hinny or jennet is the reverse cross between
  a stallion and a female donkey.
• Similar to the mule in appearance, but smaller
  and more horse like, with shorter ears and a
  longer head
• Hinnies are more difficult to produce than mules,
  and rarely will a female mule or hinny come into
  heat and produce a foal.

90
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.

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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