Clinical application of milk progesterone in the diagnosis of subfertility in suckled cows.

The potential value of milk progesterone profiles in conjunction with rectal examination in the diagnosis of subfertility in beef suckler cows was investigated. Ten of 20 cows suckled their calves three times per day and the other 10 suckled their calves continuously. Milk samples were collected twice weekly during the 21 days prior to first service and up to day 50 post mating in cows confirmed pregnant. The uterine and ovarian states of the cows were examined per rectum weekly between calving and first service. Progesterone profiles of cows conceiving to first service showed a typical smooth curve, while those of cows failing to conceive were irregular and indicated disturbances in the normal functioning of the corpus luteum.