Oestrous cycle


Animals could be categorized based on the occurrence of estrous cycle as:
o Monoestrus: Only one estrous cycle per year. eg. Wild animals.
o Polyestrus: Periodic estrous cycles throughout the year. eg. cow and sow.
o Seasonally polyestrus: Periodic estrous cycles only during a particular season.
eg. Sheep and mare.

Depending on the ovarian activity again estrous cycle is classified as:
o Regular estrous cycle: Characterised by ovulation and formation of corpus
luteum. eg. Cow, sheep, mare, bitch and sow
o Spontaneous ovulators: Ovulations are spontaneous but the corpus
luteum formed will not be functional until mating has occurred. eg., rat or mouse
o Induced ovulators: Ovulation and corpus luteum formation depends on whether
mating has occurred or not. eg. Cat, rabbit, mink.