Estrus detection with a progesterone biosensor

The objectives of this research were to demonstrate the ability of a biosensor to track the bovine estrous cycle by on–line measurement of milk progesterone and to evaluate the potential for detection of ovulatory events as compared with standard estrus detection methods. Daily measurements were made at the UC Davis research dairy on 11 nonpregnant cows, 17 to 57 days post–partum, over a period of 2 months. True ovulatory events were determined by radioimmunoassay and compared with biosensor classification, herd manager observation of estrus behavior, and activity monitor classification. The biosensor system correctly identified all 14 ovulatory events during its period of operation, but the variability at low progesterone concentrations caused 5 false positives. The herd manager identified 13 of 17 possible ovulatory events, and missed the other 4 events due to a lack of overt estrus behavior. The activity monitor detected fewer events than the herd manager (9 out of 16 possible events) and was more prone to false positives (12 vs. 4). Based on the analysis of progesterone profiles, a decision strategy to assist with reproductive management over an entire lactation is presented.