An assessment by progesterone assay of the accuracy of oestrus detection in dairy cows
McCaughey, W.J.; Cooper, R.J.
Veterinary Record 107(22): 508-510
1980
ISSN/ISBN: 0042-4900 PMID: 7445358 Document Number: 167636
The use of a milk progesterone assay in determining the extent to which dairy cows are presented for insemination at the wrong time is reported. Milk samples taken from cows at the time of insemination were subjected to plasma progesterone assay. In a preliminary study samples were obtained from 96 cows in an experimental herd at insemination. The calving rate of these cows was compared with the milk progesterone level at insemination. Eight cows with progesterone values well above the normal oestrous level (more than 0.3 ng per ml) failed to conceive. As the progesterone level at insemination rose, calving rate declined. A further 1177 milk samples taken from cows being inseminated in commercial dairy herds were also examined; 91 animals (7.7%) had milk progesterone values above those observed at normal oestrus. A negative correlation was confirmed between non-return rate and milk progesterone level at insemination. These investigations show that the proportion of cows from the national herd which have high progesterone levels when presented for insemination is similar to that found under experimental conditions and suggests that the problem of heat detection may be a relatively constant factor in reduced conception to artificial insemination.