Infertility in the Mare

1. Infertility in the Mare Lecture 5

2. Introduction • Extrinsic Factors • Lack of Use • Sub-fertile Stallion • Poor management • Intrinsic Factors • Many, many, many

3. Age • Reported to have the most significant bearing on reproductive performance • Decrease in fertility may be in part due to • An increase in transit time for sperm to reach the oviduct • Anovulatory estrus is greater in mares over 20 • Placental development and blood supply are also adversely effected

4. Chromosomal Abnormalities • Normal Chromosomal Number? • 64 or 32 pairs • Female = 64XX • Variations of a normal compliment include • 63XO – female with single X chromosome • Turner’s syndrome – common chromosomal abnormality • Characterized by small ovaries • Poorly developed uterus • Permanent anestrous

5. Hormonal Abnormalities • Hypothalamic – pituitary – ovarian homeostasis • Majority of hormonal deficiencies are associated with: • Pituitary abnormalities • Can cause: • Prolonged estrus • Prolonged di-estrus • Silent ovulations • Can eventually lead to reproductive failure • Synthetic Progesterone has proved successful in treatment

6. Follicular Atresia • Defined: • Break-down of the ovarian follicles • Group of follicles will develop normally to • ~3 cm in diameter • Failure in the emergence of a dominant follicle • Causes may include • Ovarian hypoplasia(underdevelopment or incomplete development) • Ovarian cysts • Infections, and malnutrition • Time appears to be best cure

7. Corporal Lutea Persistence Creating long or short estrous cycles Normal lifespan of CL is 14d In the absence of pregnancy, PGF2α is secreted A persistent CL is presumably present due to the failure of the release of PGF2α Could be due to uterine infection Treatment with exogenous PGF2α is normally successful

8. Anovulatory Follicles • Can be a cause of anestrous • Commonly occur in transition periods into and out of breeding seasons • Anovulatory follicles are characterized as • Large follicles which fail to rupture and ovulate • Fill with blood and persist as hematomas over a number of cycles • Presence is further complicated with their ability to secret progesterone

9. Granulosa (theca) cell Tumors • Most common tumor within the equine ovary • Important cause of anestrous • Normally effect mares between the ages of 5 and 7 • Usually associated with one ovary • Ovaries are usually polycystic or large solid structures • May weigh up to 18 pounds • Symptoms may cause • Prolonged Estrus • Testosterone producing cysts may cause: • Stallion Like Behavior • Muscular development • Removal of ovary may lead to normal reproduction

10. Ovarian Abnormalities • Ovarian Teratomas • Arising from germ cells • Contain hair, teeth, bone, etc. • Very rare • Hypoplasia • Underdevelopment • Small, immature ovaries • Often associated with chromosomal or hormonal abnormalities

11. Ovarian Abnormalities • Multiple Ovulations • Results in multiple pregnancies • Major cause of abortion • Mare is typically unable to carry twins to term

12. Infectious Infertility • Endometritis • Major cause for infertility in the mare • Inflammation of the uterine endometrium • May be caused by: • Opportunistic Bacteria • Venereal bacteria • Non-Infectious Agent • Major problem with infection is • Often undetected for long periods of time • Difficult to treat

13. Opportunistic Bacteria • Streptococcus zooepidemicus • Implicated in 75% of acute endometritis • Cause destruction of RBC • Major role in initiating infection of cervix and uterus • May promote proliferation of other bacteria • Hemolytic Escherichia coli • Second most common cause of uterine infection • Can cause acute endometritis but also severe systemic infection

14. Opportunistic Bacteria • Staphylococcus aureus • Less common • May invade reproductive tract under stress

15. Venereal Bacteria • Transferred solely via venereal route • Present within the semen and reproductive tract of both mare and stallion • Some horses may be asymptomatic • Three main type: • Taylorellaequigenitalis • Klebsiellapneumoniae • Pseudomonas aeroginosa

16. Venereal Bacteria • Taylorellaequigenitalis • Extremely Contagious • First isolated in England • Stallion is not effected but • Prime means by which it is spread • In mare • Acute endometritis • Discharge within 2 – 5 d of infection • May appear to recover but remains carrier • May also be asymptomatic

17. Venereal Bacteria • Klebsiellapneumoniae • Acute and chronic endometritis • Little to no clinical signs present • Relatively insensitive to antibiotics • Pseudomonas aeroginosa • Can be found in stallion’s semen • Clinical symptoms rare • In mares • Yellow to green discharge • Relatively resistant to antibiotics