Estrous cycle refers to the sexual cycle in all female mammals. It is characterized by periodical changes in the female reproductive organs manifested by behavioral, gross and microscopic changes.
The cycle is divided into 4 distinct yet continuous stages as follows:
1) Proestrus - active preparatory changes,
2) Estrus - ovulation and increase sexual desire,
3) Metestrus - fruitless preparation for pregnancy,
4) Diestrus - period of rest.