EQUINE REPRODUCTION

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

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

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

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

Mare Anatomy Vulva Vagina Cervix Uterus Oviducts Ovaries Left Ovary Ovary – 2X1.5” in diameter. Located on pinched in face of ovary is ovulation fossa – unique anatomical feature of equine ovary. Oviducts = ~8-12”long. Uterus – Body & 2 horns. 8” wide X 3” wide Cervix – 2-3”. Longitudinal folds Vagina – 7-9” long & 4-5” diameter Left Uterine Horn Uterine Body

MARES TERMS Anestrus Pregnant Diestrus Open Estrous Barren Estrus MARE CLASSIFICATION Pregnant Open Barren Maiden Wet Dry TERMS Anestrus Diestrus Estrous Estrus Anestrus – The period when most mares show no signs of reproductive activity at all. Diestrus – The period when the mare is not receptive to the stallion (usually lasts 17-19 days) Estrous – Entire reproductive cycle. The average length of the estrous cycle is 21-23 days (from one ovulation to the next). Estrus – Refers to “heat”, the period when the mare is receptive to the stallion (usually lasts 5-6 days).

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

Mares Cycle Percent

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

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 Photoperiod Effect Reproductive activity in spring is stimulated by an increasing photoperiod Mechanism Alteration of hormone secretion by the pineal gland and hypothalamus Anterior pituitary Decreasing gonadotropins Increasing gonadotropins Ovaries

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

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 Increased photoperiod stimulates the hypothalamus and pituitary Pituitary hormones (especially FSH) induce follicular development Note – Multiple follicles on ovary.

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

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 Note: 5 days estrus. To estimate the next cycle, count 21 days from the 1st day of estrus or 15 days from the last day of estrus.

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

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 Ovulation normally occurs when follicle reaches 4-5 cm

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

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.

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

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

Light Stimulus 16 hrs daylight per day 30-60 days

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 Normalization of estrus in the early breeding season. Control of estrus in mares exposed to artificial light. Regulation of estrus in cycling mares. Appointment breeding. Estrus suppression in performance mares. Delaying foal heat. Pregnancy maintenance.

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

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

Cooled Shipped Semen ADVANTAGES Cost Genetics Disease DISADVANTAGES Technology/management Stallion variability Common Problems Inability to obtain semen Poor quality semen Reordering semen Failure to predict ovulation ADVANTAGES Cost No mare care or shipping expenses Genetics Potential access to higher quality Disease Decreased transmission of std’s DISADVANTAGES Cost & shipment Veterinary/technician expenses Technology/management Competent individuals Stallion variability DISADVANTAGES Stallion variability

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

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

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

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

Gestation Length Normal: 335-342 days Summer 7-10 days shorter Winter - longer

GROWTH CURVE CR in cm Gestation age in days

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

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

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

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

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