Timing the insemination of beef cattle

Abstract Calving rates of beef cows were determined from first inseminations at various intervals of time after estrus was first observed. For 1326 calves resulting from first inseminations between 12 and 29 hr after the detection of estrus, the actual calving rate was 63.4% for 2091 cows. As determined from a prediction equation, 68.8% was the optimum calving rate for inseminations at 20 through 21 hr after estrus detection. The ranges in predicted calving rates were 65.9 to 68.8% for inseminations at 16 through 25 hr, 57.0 to 62.2% for inseminations at 12 through 15 hr, and 57.0 to 62.2% for inseminations at 26 through 29 hr after estrus detection.