Hormonal Causes of Infertility in Animals

Hormonal or functional causes of infertility mostly affect individual animals within a herd. However, when a larger group of animals in a herd are affected, they frequently reflect some other problem such as inherited factors; nutritional deficiencies or excesses; social influences which may arise from modern husbandry methods.

Hormonal diseases may include cystic ovarian degeneration, failure of estrum or anestrum and repeat breeders.

Cystic Ovarian Degeneration

Cystic ovaries degeneration, one of the most common condition causing infertility in dairy cattle is characterized by follicular cysts, luteal cysts and cystic corpora lutea.

Follicular and luteal cysts are basically anovulatory cysts while cystic corpora lutea are ovulatory cysts.

Anestrum

Following puberty, the cow should cycle regularly at approximately 21-day intervals unless interrupted by pregnancy and for a short period in the puerperium. The occurrence of estrus signs is the only way to tell that the animal is cycling. It is possible that estrus signs are occurring but are not being observed which is purely a management problem.

True Anestrus

In true anestrus the ovaries are quiescent and nonfunctional. The reasons for the failure of cyclicity may be insufficient release or production of gonadotrophins to cause follicle development, or it may reflect the failure of the ovaries to respond, but the latter is unlikely.

Anestrum due to Subestrus or Silent Estrus

Subestrus or silent estrus most commonly occurs when the first and second ovulations postpartum are not preceded by behavioural signs of estrus.

The causes for silent estrus or subestrus could be due to:

• Improper heat detection
• Genetic predisposition
• Climates where incidence is more common in temperate climates and more common in the winter than in the summer months
• Nutritional deficiencies such as deficiency of ß-carotene, phosphorus, copper cobalt.
• Overweight

Anestrum due to Persistent Corpus Luteum

Persistent corpus luteum occurs when there is failure in the production or release of endogenous luteolysin. Conditions that result in persistence of corpus luteum are:

• Pregnancy
• Pyometra
• Mucometra or hydrometra
• Mummification
• Maceration

It is important to remember that persistent corpus luteum does not occur in the presence of a normal non-pregnant uterus. Many veterinarians tend to call wrongly a cyclic CL as persistent CL.

The condition, once diagnosed, can be readily treated with PGF2 α or a synthetic analogue, provided that the clinician is confident that the cow is not pregnant; estrus will occur in 3-5 days.