Factors Affecting Oestrous Cycle
Several factors influence the oestrous cycle in animals, affecting its duration, frequency, and regularity.
These factors affecting oestrous cycle are:
- Nutrition
- Seasonal influences and light
- Temperature
- Age
- Systematic diseases
- Pathology of uterus and cervix
- Endocrine disturbances
- Miscellaneous causes
- Stress
- Character of Work
Nutrition
Inanition or starvation caused by lack of energy or nutritional deficiency impairs or prevents secretions of gonadotrpoic hormones from pituitary gland.
Seasonal Influences and Light
Seasonal breeding is regulated by light through the medium of eyes on the hypothalamus and anterior pituitary gland. The total daily amount of light is important in control of the onset of oestrous cycle. This is called as sexual photoperiodicity. In sheep and goat decreased day light influences onset of estrous. In mares increased total daily hours of light will hasten the onset of oestrous cycle.
Temperature
Excessive heat during summer months causes decreased thyroid activity which is directly reduces reproductive efficiency. In cattle under hot conditions length of the oestrous cycle is increased to 25 days as compared to 20-22 days in cool weather. Excessive exposure to cold may cause failure of oestrous cycle in young growing animals.
Age
In cattle and swine the young female usually has a slightly shorter length of oestrous cycle than the adult animals. Similarly causes cessation of oestrous cycle.
Systematic Diseases
Severe chronic wasting diseases like TB, Johne disease, Mange, Actinomycosis, severe parasitism and other diseases cause debility and emaciation resulting in cessation of estrous cycle.
Pathology of Uterus and Cervix
In cattle, Pathological conditions of Uterus and Cervix like pyometra, foetal maceration, mummification causes persistence of corpus luteum and cessation of oestrous cycle.
Endocrine Disturbances
Endocrine regulation by various hormones is essential for a timely oestrous. Endocrine disturbances leading to cystic ovaries or pituitary, ovarian and adrenal tumors affect the length of the oestrous cycle.
Miscellaneous Causes
Pregnancy causes physiological cessation of oestrous cycle. The presence of males hastens onset of estrous, infusion of iodine compounds into the uterus shortens the oestrous cycle.
Stress
Transport stress induce follicular growth and ovulation in large animals 4-6 days after moving.
Character of Work
Work or race horses under severe work do not develop regular oestrous cycle. Cows under heavy milk production may not have oestrous cycle for 3-4 months due to negative energy balance.
