Oestrus during pregnancy in the cow

Abstract

Oestrus during pregnancy has several important practical implications for herd management: in the absence of accurate pregnancy diagnosis, animals which show oestrus may be thought to be repeat breeders and sold as infertile. Alternatively, the insemination of already pregnant cows may result in the loss of the embryo or fetus, and the consequent lengthening of the calving interval.

The mechanism responsible for the exhibition of oestrus during pregnancy is not known. In the oestrus cycle in non-pregnant cows, hormonal changes are responsible for the manifestation of oestrus behavior, but no information is available on the hormonal status of the pregnant cows showing oestrus. A method for the diagnosis of oestrus during pregnancy is desirable; the present study was designed to examine the potential use of the characteristics of the cervical mucus, in particular the ferning pattern, and the concentration of progesterone in milk. The characteristics of the behavior of cows showing oestrus during pregnancy, especially their interactions with other cows and the bull, were also studied.