Similarly to other domestic animals the oestrus cycle in the cow can be divided into four phases:
In late proestrus, the influence of oestrogens on the reproductive tract and behaviour of the cow can be observed.
Traditionally considered as day 0 of a new cycle
The dominant follicle reaches its maximum growth, matures and ovulates.
Ovulation takes place approximately 30h after the onset of oestrus and after the behavioural signs of oestrus have ceased.
Ovulation is induced by high LH concentrations (preovulatory LH peak).
Oestrus is also called heat and lasts on average 4-24 hours. During oestrus the cow/heifer is receptive to a bull and stands for mating (standing heat).
Behavioural signs of oestrus are due to the influence of oestrogens:
During this time a phenomenon known as “metoestrus bleeding” occurs in approx. 90% of heifers and not more than 45% of cows. Patches and streaks of blood are seen in the vaginal mucus staining the tail and perineum.
Remember: the presence of blood in the mucus is not an indication of conception or a failure to conceive.