Comparison of estrus detection techniques in dairy heifers.

Detection of estrus was by twice daily heat checks, heat mount detectors, and pedometers. Changes of progesterone concentrations in blood plasma were monitored three times weekly. Method of detection did not affect observed cycle length. Efficiency of estrous cycle detection (as defined by changes of progesterone concentration in plasma) ranged from 67% to 74%. Combinations of two techniques ranged in efficiency from 84% to 93%. Accuracy of estrus detection (based on changes in progesterone concentration) varied widely, from 29% to 95%. Accuracy of twice daily heat checks and pedometer activity detection at two standard deviations greatly exceeded the other techniques. Heat checks and pedometer detection combined gave both high efficiency and high accuracy of detection.