The Use of Milk Progesterone Analysis in the Study of Oestrus Detection, Herd Fertility and Embryonic Mortality in Dairy Cows

Abstract

SUMMARY A milk progesterone radioimmunoassay was used for three studies on fertility in seven dairy herds. Daily sampling of 29 cows in one herd over a 30-day period revealed peaks of progesterone around the time of oestrus with 54% of the animals having a progesterone concentration in whole milk > 3 ng/ml on the day of insemination. The conception rate was 83%; cows conceiving and not conceiving had mean progesterone levels of 5.6 ± 1.18 ng/ml, n = 20 and 4.35 ± 2.22 ng/ml, n = 4 respectively. These peaks were not apparent at oestrus in animals of five other herds. Progesterone samples were collected at 10-day intervals from a 37 cow herd during the post-partum period and early pregnancy. This type of trial, which proved adequate to distinguish cyclic from acyclic cows and to assess the oestrus detection rate, could be used by veterinary surgeons to assist their treatment of infertile herds. Twice weekly sampling of 535 cows during early pregnancy indicated that embryonic mortality occurred in 12% of animals between 31 to 59 days after insemination. During the first 30 days of pregnancy no difference was found in the mean progesterone levels of 57 normal cows and 23 in which embryonic mortality occurred. Following this, progesterone levels remained in the normal range in the latter group until a steep decline to basal values indicated that embryonic mortality had occurred.