Drug Actions-Progesterone Target Cells: Neurons of Hypothalamus Progesterone Mode of Action: Steroid Pathway Feedback Mechanism: Negative Feedback

Drug Action-Human Chorionic Gonadotropin (HCG) HCG Target Cells: Ovary Mode of Cellular Pathway: 2 nd Messenger-cAMP Feedback: Positive (increase P4)

Percentage of mares ovulating at various time intervals after administration of hCG.

Hormone Management Prostglandins –Only works on mature corpus luteum (~ 5 d after ovulation) –Mare will come into heat 2-5 days later. –The time to estrus varies depending on follicular development on the ovary. Lutalyse –Dose is 5-10 mg (1-2 cc/mare) IM. –Side effects Estrumate –Dose is 200 mcg/mare IM. –Fewer side effects

Single Prostaglandin Injection Prostaglandin during luteal phase results in heat ~3 days, ovulation in 3-16 days Response rate of ~50% Mares with excessive side effects can get same results w/ 1/10 dose PgF Long estrus Ovulation 10 d PgF Estrus 2-4d Ovulation 7-9d PgF Ovulation hr PgF Follicle regresses Ovulation of new In 9 d

Mare Evaluation Diagnostic tests & things to consider Age, physical condition, & history of mare. Examination of the mares external reproductive conformation. Palpation of uterus. Speculum exam of the cervix. Culture of uterus.

Mare Evaluation Diagnostic tests & things to consider Examination of uterine cells (Cytology). Endometrial biopsy. Ultrasonography –Diagnosis of delayed uterine clearance. Endoscopy: visually inspecting inside the uterus. Oviduct blockage exams.

Uterine Biopsy Category I – No pathological changes and should be of normal fertility. Estimated foaling rate = 80-90% Category IIA & IIB -Inflammatory changes severe enough to decrease fertility and may be accompanied by fibrosis. Estimated foaling rate = 50-80% Category III-Drastically reduced fertility. Uteri may be incapable of supporting fetal development. Estimated foaling rate = <10%

Poor Perineal Conformation Common in older mares Associated with endometritis Management –Caslick’s procedure

Reasons Why A Mare May Not Come In To Heat Lactation anestrus Silent heat Multiple ovulations

Reasons Why A Mare May Not Come In To Heat Diestrous ovulations

Reasons Why A Mare May Not Come In To Heat Persistent corpora lutea,

Reasons Why A Mare May Not Come In To Heat lAbortion after day 35 of pregnancy lRecent anabolic steroid administration lGranulosa cell tumor lWinter anestrus & spring transition

Old vs Young Reduced pregnancy rates, higher EED Fewer oocytes/embryos collected Oviductal embryos smaller & of reduced quality Uterine embryos - reduced collection rates and quality, delayed development years –shorter follicular phase –smaller follicles –more double ovulation's 20+ years –longer follicular phase –intermittent ovulation's –failure to ovulate

Mare Infertility Ovary –No follicular growth –Ovulatory failure –Oocyte quality –Chromosomal abnormalities Oviduct –Blockage –Infection/inflammati on –Failure to pickup oocyte –Poor environment Cystic Ovary Ovarian hematoma

Uterus Inflammation Infection Fibrosis (scar tissue) Poor environment Mechanical

Endometritis Inflammation of the tissue lining the uterus Usually associated with infection Predisposing Factors: –Poor perineal anatomy –Trauma (parturition or breeding) –Inadequate hygiene –Failure of uterine defense mechanisms (especially uterine motility/clearance)

Inflamed cervix of a young, nulliparous mare 5 hours after intrauterine infusion of bacteria. Donated by Dr John Hughes

Endometrial Cysts Obstructed/dilated lymphatics Common in older mares Risk to pregnancy is low Confused with pregnancy on ultrasound

Cervix Tears Adhesions Fibrosis Inflammation

Vagina, vulva, vestibule Urine pooling Air Vaginitis Foreign material

Urine Pooling Most common in older mares Urine refluxes forward into vagina Urine enters cervix during estrus and may pass into uterus Results in endometritis and infertility Treatment –Correct predisposing factors –Uterine lavage –Urethral extension surgery

Infectious Infertility in Mares lSigns lIrregular estrus cycles lAnestrus lMatted tail hair & crusty hair on hindquarters lFailure to conceive lVisible, slimy milky or creamy white exudate on vulva, tail, inner thighs, vaginal floor lRed mucus membranes

Primary Causes of Abortion Twins –Abortion generally occurs in late pregnancy (7 months to term) Equine herpes virus Placentitis

Factors affecting incidence of twins Breed Reproductive status –lower incidence in lactating mares Age –higher incidence in older mares Repeatability Heredity

Incidence of multiple ovulation's