LECTURE 5 Infertility in the Mare

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

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

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

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

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

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

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

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

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

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

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

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

Opportunistic Bacteria Staphylococcus aureus  Less common  May invade reproductive tract under stress

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:  Taylorella equigenitalis  Klebsiella pneumoniae  Pseudomonas aeroginosa

Venereal Bacteria Taylorella equigenitalis  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

Venereal Bacteria Klebsiella pneumoniae 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