Plasma progesterone levels as an early pregnancy test in beef cattle

Abstract

The accuracy of an early pregnancy test based on plasma progesterone concentrations was examined in a herd of 153 beef cows in which pregnancy status was confirmed by rectal examination three months after the end of an artificial insemination programme. At threshold progesterone levels of 1.50, 1.75 or 2.00 ng/ml the percentages of correct diagnoses in pregnant cows were 93.8, 93.8 and 90.1 and for non pregnant cows were 77.8, 79.2 and 84.7 respectively. At a threshold level of 1.50 ng/ml sixteen (22.2%) non pregnant cows were incorrectly diagnosed as pregnant, and on the basis of oestrus records could be classified into: 1. 1. Cows with cycle lengths (24 days) longer than the average. (Mean progesterone concentration 2.55 ± 0.64 ng/ml). 2. 2. Cows with mean cycle lengths of 39 days, in which apparent embryonic mortality had occurred (Mean progesterone concentration 3.47 ± 0.84 ng/ml). 3. 3. Cows not exhibiting oestrus during the remainder of the observation period, in which late embryonic or foetal mortality had apparently occurred (Mean progesterone concentration 4.89 ± 0.70 ng/ml).