Oestrus every 21 days
If the cow is ready for mating, she is in oestrus. She is in oestrus at regular intervals of 21 days throughout the year. Over a period of one to three days her behavior changes as do her reproductive organs as the concentration of the oestrus hormone oestrogen increases in her blood. This is formed from the maturing follicle on the ovary. It triggers the typical oestrus signals in the cow.
In this chapter on oestrus you will find information on:
- the signals during the different phases of oestrus
- for the time-based connection between oestrus and insemination
- and tips for oestrus monitoring
- Which factors have a positive or negative influence on a clear oestrus
Over a period of one to three days the behavior and reproductive organs of your cow change when the concentration of the oestrus hormone oestrogen increases in her blood. This hormone is formed from the maturing follicle on the ovary. It triggers the typical oestrus signals in the cow. During oestrus these signals become increasingly stronger or change in their manifestation.
Therefore a differentiation between the different oestrus phases is made as follows:
Agitation in pre-oestrus
Two to three days before the main oestrus period the cow about to go into oestrus attracts attention because she increases her step count, becomes more agitated and forms small groups with other cows in the herd. She smells the vulva area of other cows, curls the upper lip upwards and shows the flehmen response. Via scents she can perceive the cycle status of others. In many animals milk yield falls. The vulva appears swollen and reddens since it its blood supply has increased. Oestrus mucus is initially watery and then thin. It would still be too early to inseminate.
These cow signals are typical indications for a cow in pre-oestrus.
- Head laying
Standing reflex in main oestrus
The bigger the follicle becomes in progressive oestrus on the ovary, the more oestrogen it produces and the oestrus signs become all the clearer. Via the blood the oestrus hormones are distributed around the whole body and trigger the corresponding changes. The cow acquires a fixed gaze, raises her ears and arches her back downwards. She mounts the other animals from behind and on the head. The most important signal for a cow coming into oestrus is the standing reflex which signals the start of oestrus. At this time the cow does not resist when other animals mount her. She “stands”.
These cow signals are typical indications for a cow in oestrus.
- Standing reflex
- Oestrus mucus
Post-oestrus occurs after ovulation
In the third oestrus phase of “post-oestrus” the cow no longer stands when she is mounted. She walks away or turns away. The standing reflex has ended. Also her remaining behavior has returned to normal, the indications of oestrus have subsided and the cow becomes calm. At this time some animals manifest bloody mucus on and around the vulva or on the tail. These animals “bleed”.