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Drug Actions-Progesterone

Drug Actions-Progesterone. Progesterone. Target Cells: Neurons of Hypothalamus. 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.

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Drug Actions-Progesterone

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

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

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

  4. 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 Hormone Management

  5. 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 Ovulation 12-24 hr PgF Estrus 2-4d Ovulation 7-9d PgF Follicle regresses Ovulation of new In 9 d PgF Long estrus Ovulation 10 d

  6. 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.

  7. 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.

  8. 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%

  9. Poor Perineal Conformation • Common in older mares • Associated with endometritis • Management • Caslick’s procedure

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

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

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

  13. Reasons Why A Mare May Not Come In To Heat • Abortion after day 35 of pregnancy • Recent anabolic steroid administration • Granulosa cell tumor • Winter anestrus & spring transition

  14. Reduced pregnancy rates, higher EED Fewer oocytes/embryos collected Oviductal embryos smaller & of reduced quality Uterine embryos - reduced collection rates and quality, delayed development 15-20 years shorter follicular phase smaller follicles more double ovulation's 20+ years longer follicular phase intermittent ovulation's failure to ovulate Old vs Young

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

  16. Uterus • Inflammation • Infection • Fibrosis (scar tissue) • Poor environment • Mechanical

  17. 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) Endometritis

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

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

  20. Cervix • Tears • Adhesions • Fibrosis • Inflammation

  21. Vagina, vulva, vestibule • Urine pooling • Air • Vaginitis • Foreign material

  22. 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 Urine Pooling

  23. Infectious Infertility in Mares • Signs • Irregular estrus cycles • Anestrus • Matted tail hair & crusty hair on hindquarters • Failure to conceive • Visible, slimy milky or creamy white exudate on vulva, tail, inner thighs, vaginal floor • Red mucus membranes

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

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

  26. Incidence of multiple ovulation's

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