Evaluation of reproductive performance using milk progesterone assay

Dairy herds (472) in the northeastern United States of America were surveyed to evaluate reproductive performance. Error of oestrus detection (>> 1 ng/mL of milk progesterone) on the day of insemination was 5.1% for 4558 cows. 'Standing' and 'riding other cows' were the most accurate signs of oestrus. Of cows in or near oestrus when inseminated, 28.1% were open three weeks later, 12.9% were probably open, and 59% were probably pregnant according to milk progesterone analysis. Post-partum days to first insemination and conception rates showed positive correlation. Concentrations of progesterone in milk samples collected 21 to 24 days after service allowed prediction with 88.6% accuracy that a cow was pregnant and with 93.9% accuracy that she was not. By rectal palpation, veterinarians predicted with 92.5% accuracy that a cow was pregnant. (author). 12 refs, 4 tabs