Transcript Lecture 5 - Infertility in the Mare
Infertility in the Mare
L E C T U R E 5
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