Hormonal Causes of Infertility in Cattle

Study Notes

Infertility can have various causes including congenital, pathological, and hormonal factors.
Hormonal causes include cystic ovarian disease, delayed ovulation, silent heat, and anestrus.

Anestrus (absence of estrus) is not a disease in cattle but a symptom of many reproductive disorders.
Anestrus can be physiological or pathological.
Physiological anestrus includes occurrences during pregnancy, postpartum, before puberty, and when out of breeding season in seasonal breeders or when heat is not observed.
Pathological anestrus has primary and secondary forms.
Primary anestrus includes: bilateral ovarian aplasia, bilateral complete ovarian hypoplasia, freemartinism, hermaphrodite, and male pseudo hermaphrodites.
Secondary anestrus includes: persistent cystic CL, inactive ovary, and silent heat.

Pregnancy inhibits estrus through progesterone production, which prevents FSH secretion by the ovary.
The presense of an embryo can prevent the uterine release of PG and helps maintain corpus luteum.
The presence of the CL prevents the uterus from releasing PGE and PGE2, which helps maintain the CL as luteotropic action.
Silent heat (sub-estrus): affected female fails to express behavioral signs of estrus.
Silent heat still contains typical cyclical changes in the ovaries.
It accounts for most of the cases of anestrus, especially in hot climates
Silent heat causes economic losses due to additional open days for breeding.
The physiological basis for silent heat is not fully known. Possible causes for silent heat include inheritance of poor regulatory mechanisms in some animals, a required higher threshold of estrogen levels in some animals to display heat symptoms, lactation, imbalanced feed quality/quantity, hot climates, pain-related diseases, hard work, and lack of exercise among others.
Common causes include pain, diseases (such as footrot), or other stress factors.
Buffaloes experience silent heat more commonly than cows.

Retained CL is the continuous presence of the CL beyond its normal lifespan, without regular cyclical changes in the ovary or uterus.
True persistent CL means the presence of the CL in the ovary without changes in the genital tract.
False persistent CL is the presence of an existing CL in the ovary after breeding, with uterine changes.
True or false persistent CL is often associated with anestrus.
Cyclic CL usually regresses at day 18, while pregnancy CL regresses approximately 3–4 weeks after parturition.
Retained/persistent CL is generally associated with high lactation cows who may have high prolactin levels, which helps to maintain the CL.
High prolactin levels can suppress FSH secretion, thereby preventing ovulation.
False Persistent CL can occur due to uterine distension, White heifer disease, embryo/fetal death which can lead to the abortion of a pregnancy.
Other factors causing false persistent include: mucus/pus in the uterus, dead fetus, closed/open pyometra, hydrometra, Segmental aplasia, uterus unicornis and other related issues.
Days of pregnancy are categorized into stages ranging from early embryonic death to full-term.

Clinical observation of Anestrus
Exclusion of pregnancy using rectal examinations
Detection of abnormal uterine conditions through rectal examination
If CL is present on the same side of the ovary and does not change, it might be a retained CL.
Re-examination of the animals between days 7 and 10 is necessary.

Exclude pregnancy before any treatment.
Common treatment is injection of PGF2α (luteolytic factor) which induces estrus within 3-5 days.
If treatment does not work repeat dose after 10 days.
Medication doses may vary depending on the species (e.g., 500 µg cloprestenol for cows).

Maintain accurate records and good herd management of the entire breeding stock.
Improvement of management practices like nutrition/housing/medical care is necessary
Close observation to detect heat by clever stockmen and laymen should occur.
Additional training in the identification of symptoms can assist in this detection.
Encourage workers participation in the diagnosis process.
Long-term observation of the entire herd is helpful.

Avoid enucleation of the CL.
Treat condition specifically if the uterus contains pus, mucus, or dead fetus.
Treat condition with uterine regression of the CL via hyperemia induction treatment (e.g. canthradine, lugols, warm water.).