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EQUINE REPRODUCTION

EQUINE REPRODUCTION. BOOK BOOKING FEES STUD FEE FOAL GUARANTEE Live Foal Return Color. WET/DRY CARE BREEDER Thoroughbred Other breeds DEATH & SALES CLAUSE CHUTE FEE. TERMINOLOGY. Stallion Physiology. Sperm Production. Sperm Output and Production is influenced by: Season

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EQUINE REPRODUCTION

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  1. EQUINE REPRODUCTION

  2. BOOK BOOKING FEES STUD FEE FOAL GUARANTEE Live Foal Return Color WET/DRY CARE BREEDER Thoroughbred Other breeds DEATH & SALES CLAUSE CHUTE FEE TERMINOLOGY

  3. Stallion Physiology

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

  5. 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

  6. Mare Anatomy • Vulva • Vagina • Cervix • Uterus • Oviducts • Ovaries Left Ovary Cervix Vagina Oviduct Left Uterine Horn Uterine Body

  7. TERMS Anestrus Diestrus Estrous Estrus MARE CLASSIFICATION Pregnant Open Barren Maiden Wet Dry MARES

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

  9. Mares Cycle Percent

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

  11. 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

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

  13. 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

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

  15. Estrous Cycle

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

  17. 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

  18. 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

  19. 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.

  20. Signs of Estrus • Most consistent • Elevated tail raise • Winking • Other supporting signs • Leaning • Squatting • Standing still • Urinating

  21. Manipulation Methods • Artificial lighting • Shortening Late Transition • Inducing Ovulation • Estrus synchronization • Estrus Synchronization & Ovulation Induction

  22. 16 hrs daylight per day 30-60 days Light Stimulus

  23. 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

  24. PGF2Lutalayse or Estrumate • Shorten the interval between estrous periods • Treatment of a maintained corpus luteum • After foal heat • Estrous synchronization with prostaglandins

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

  26. 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 Cooled Shipped Semen

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

  28. Embryo Transfer • Synchronization of donor and recipient mare • Embryo flushing • Embryo transfer procedure

  29. 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

  30. Ultrasound, 14-18 days ID twins ID placental development Re-evaluate, 40 days Monitor Placental function & fetal growth Pregnancy Evaluation

  31. Gestation Length • Normal: 335-342 days

  32. GROWTH CURVE CR in cm Gestation age in days

  33. 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

  34. 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

  35. Stages of Parturition • Stage 3 (< 3 hrs) • Onset: delivery of fetus • End: passage of the fetal membranes

  36. 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 foal’s blood • Takes ~ 12 hours for all antibodies ingested in colostrum to show up in the blood

  37. 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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