EQUINE REPRODUCTION

TERMINOLOGY s BOOK s BOOKING FEES s STUD FEE s FOAL GUARANTEE sLive Foal sColor s WET/DRY CARE s BREEDER sThoroughbred sOther breeds s DEATH CLAUSE s CHUTE FEE

Stallion Physiology Onset of sexual maturity10-24 mo Life span of sperm in female tract 2-4 days Survival time with fertilizing capacity 1-2 days Sperm output Semen volume/ejaculate ml # sperm/ejaculate X

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

Mare Anatomy Vulva Vagina Cervix Uterus Oviducts Ovaries Left Ovary Oviduct Left Uterine Horn Uterine Body CervixVagina

TERMS Anestrus Diestrus Estrous Cycle Estrus MARE CLASSIFICATION Pregnant Open Barren Wet Dry MARES

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

Photoperiod Effect Reproductive activity in spring stimulated by an increasing photoperiod Mechanism –Altered hormone secretion by pineal gland – edu/hbooks/pathphys/end ocrine/otherendo/pineal.h tml

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

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

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

Estrous Cycle SunMonTueWedThuFriSat

Go to CSU site and discuss GONADOTROPINS What does LH and FSH stand for? hbooks/pathphys/endocrine/h ypopit/lhfsh.html

Estrus Follicular Development & Ovulation Anterior Pituitary – FSH - follicular growth Pituitary – LH – maturation of follicle & ovulation Follicles reach 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

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 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 –Elevated tail raise –Winking – Uv21Cwhttp:// Uv21Cw Other signs –Squatting –Urinating whitish –Video of mare interaction Z9JyEz4 Z9JyEz4

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

Light Stimulus 14.5 hrs daylight per day (also long days done for hair coat control) days

Progesterone or related compounds l Regumate – most common l Normalization of estrus l Estrus synchronization l Long-term suppression of estrus l Pregnancy maintenance

Lutalyse or Estrumate u Shorten interval between estrous periods u Break down the CL corpus luteum u Estrous synchronization with prostaglandins er.com/Content.plx?P=A& C=301&A=2720&S=0 er.com/Content.plx?P=A& C=301&A=2720&S=0

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

Cooled Shipped Semen ADVANTAGES Cost Genetics Disease DISADVANTAGES Cost Technology/mgmnt Stallion variability Common Problems Inability to obtain semen Poor quality semen Reordering semen Failure to predict ovulation

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

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

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

Gestation Length Normal: 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 –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 –Foaling video 7min com/watch?v=3RS Av_JIQMo com/watch?v=3RS Av_JIQMo

Foals and Immunity Colostrum (first milk) - antibodies 1-2 pts of high quality colostrum If adequate passive transfer occurs there will be over mg/dl IgG Immunoglobulin antibodies in foal’s blood Takes ~ 12 hours for all antibodies ingested in colostrum to show up in the blood