EQUINE REPRODUCTION

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EQUINE REPRODUCTION
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TERMINOLOGY

• BOOK
• BOOKING FEES
• STUD FEE
• FOAL GUARANTEE
• Live Foal
• Return
• Color

• WET/DRY CARE
• BREEDER
• Thoroughbred
• Other breeds
• DEATH SALES CLAUSE
• CHUTE FEE

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Stallion Physiology
Onset of sexual maturity 10-24 mo
Life span of sperm in female tract 2-4 days
Survival time with fertilizing capacity 1-2 days
Sperm output
Semen volume/ejaculate 20-100 ml
Sperm concentration X 106 30-800 ml
sperm/ejaculate X 109 6
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Sperm Production

• Sperm Output and Production is influenced by
• Season
• Testicular size
• Age
• Frequency of ejaculation
• Behavior

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Number of Sperm Depends On

• Seasonal Influences (Photoperiod)
• Effected Areas
• Ejaculate volume
• Sperm numbers
• Total sperm/ejaculate
• Sperm motility
• Willingness to breed
• Mounts before breeding
• Scrotal size
• Testosterone production

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Mare Anatomy

• Vulva
• Vagina
• Cervix
• Uterus
• Oviducts
• Ovaries

Left Ovary
Cervix
Vagina
Oviduct
Left Uterine Horn
Uterine Body
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MARES

• MARE CLASSIFICATION
• Pregnant
• Open
• Barren
• Maiden
• Wet
• Dry

• TERMS
• Anestrus
• Diestrus
• Estrous
• Estrus

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The Open Mare

• Evaluate reproductive history
• Establish the time of year to breed
• Mare Plan
• Diagnose possible problems
• Implement problem management
• Establish estrus calendar

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Mares Cycle
Percent
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Photoperiod Effect

• Reproductive activity in spring is stimulated by
  an increasing photoperiod
• Mechanism
• Alteration of hormone secretion by the pineal
  gland and hypothalamus

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J F M A M J J A
S O N D
Increasing day length
Decreasing day length
Receptors in eye
Neuropathway
Neuropathway
Pineal gland
Decreasing melatonin
Increasing melatonin
Hypothalamus
Increasing GnRH
Decreasing GnRH
Anterior pituitary
Decreasing gonadotropins
Increasing gonadotropins
Ovaries
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Transition Period

• Increased photoperiod stimulates the hypothalamus
  and pituitary
• Pituitary hormones (especially FSH) induce
  follicular development

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Transition

• 1-3 waves of follicles develop regress
• Estrogens produced by developing follicles
• Irregular/prolonged estrus exhibited
• 1 follicle eventually ovulates
• Thereafter, mares ovulate at 21-day intervals

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• 21-day estrous cycle
• Estrus 5-7 d
• Diestrus 14-16 d

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Estrous Cycle
Sun Mon Tue Wed Thu Fri Sat
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
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Estrus

• Follicular Development
• Ovulation
• Anterior Pituitary FSH - follicular growth
• Pituitary LH maturation of follicle
  ovulation
• Follicles reach 20-25 mm in diameter, secrete
  estrogen.

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Prediction of Ovulation

• Number of days in heat
• Growth rate of largest follicle
• Average 3-5 mm/day
• Size of largest follicle
• Softness of preovulatory follicle
• Ultrasound image

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Diestrus

• Corpus Luteum Formation
• Corpus luteum - secretion of progesterone.
• Progesterone - responsible for keeping the mare
  out of heat and for maintaining pregnancy.
• Prostaglandin Release
• Prostaglandin (PGF) - released from the uterus of
  a non-pregnant mare 14-16 days after ovulation

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Postpartum Estrus

• Foal Heat
• Fertile as compared to other species.
• Breeding may be necessary to maintain the 12 mo.
  Foaling interval.
• May be necessary to back up foaling.

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Signs of Estrus

• Most consistent
• Elevated tail raise
• Winking
• Other supporting signs
• Leaning
• Squatting
• Standing still
• Urinating

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Manipulation Methods

• Artificial lighting
• Shortening Late Transition
• Inducing Ovulation
• Estrus synchronization
• Estrus Synchronization Ovulation Induction

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Light Stimulus

• 16 hrs daylight per day
• 30-60 days

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Progesterone or related compounds

• Regumate most common
• Normalization of estrus
• Regulation of estrus
• Estrus synchronization
• Long-term suppression of estrus
• Delay foal heat
• Pregnancy maintenance

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PGF2? Lutalayse or Estrumate

• Shorten the interval between estrous periods
• Treatment of a maintained corpus luteum
• After foal heat
• Estrous synchronization with prostaglandins

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Breeding Methods

• Pasture Breeding
• Hand Breeding
• Artificial Insemination
• Fresh semen
• Cooled, shipped semen
• Frozen semen

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Cooled Shipped Semen

• ADVANTAGES
• Cost
• Genetics
• Disease
• DISADVANTAGES
• Cost
• Technology/management
• Stallion variability

• Common Problems
• Inability to obtain semen
• Poor quality semen
• Reordering semen
• Failure to predict ovulation

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Frozen Semen

• Success of Frozen Semen
• Fertility of stallions semen
• Fertility of the mare
• Skill of the veterinarian/technician
• Maximum Success
• Client communication
• Choose ideal candidate
• History of stallion

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Embryo Transfer

• Synchronization of donor and recipient mare
• Embryo flushing
• Embryo transfer procedure

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TEN FACTORS INFLUENCING PREGNANCY PREGNANCY
LOSS PER CYCLE

• MARE AGE
• BARREN REPRODUCTIVE STATUS
• EARLY BREEDING DATE
• LATE BREEDING DATE
• BREEDING FREQUENCY
• PROSTAGLANDIN FACTOR
• UTERINE CULTURE CYTOLOGY
• EFFECT OF SEMEN EXTENDER
• POST-BREEDING ANTIBIOTIC INFUSIONS
• TWINS

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Pregnancy Evaluation

• Ultrasound, 14-18 days
• ID twins
• ID placental development
• Re-evaluate, 40 days
• Monitor Placental function fetal growth

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Gestation Length

• Normal 335-342 days

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GROWTH CURVE
CR in cm
Gestation age in days
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Late Pregnancy

• Abdomen greatly enlarged
• Ventral edema
• Mammary gland enlargement 2-4 wk
• Gluteal muscles relax 7-10 d
• Teats fill with milk 4-7 d
• Waxing of teat ends 1-4 d
• Vulva soft relaxed 1-2 d

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Stages of Parturition

• Stage 1
• Onset initial uterine contractions
• End rupture of chorioallantois (water bag)
• Stage 2
• Onset rupture of chorioallantois
• End delivery of fetus

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Stages of Parturition

• Stage 3 (lt 3 hrs)
• Onset delivery of fetus
• End passage of the fetal membranes

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Foals and Immunity

• Colostrum (first milk) - antibodies
• 1-2 pts of high quality colostrum
• If adequate passive transfer occurs there will be
  over 400-800 mg/dl IgG in foals blood
• Takes 12 hours for all antibodies ingested in
  colostrum to show up in the blood

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Key points

• First two weeks- lay the groundwork by ensuring
  adequate colostrum
• Preventative health program in place
• Appropriate nutrition
• Problems must be addressed rapidly when they
  arise. No time for a wait and see attitude

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