MANAGEMENT CHANGES TO REDUCE DYSTOCIA IN VIRGIN BEEF HEIFERS

A program to reduce the incidence of dystocia in heifers consisted of estrous synchronization followed by insemination with semen from sires with a low Expected Progeny Difference (EPD) for birthweight (calving-ease) bulls. The program was applied to replacement heifers from five beef herds were subjected to the program. Artificial insemination programs resulted in pregnancy rates ranging from 41 to 56%, with an across-herd mean of 50.7%. Parturition from matings to calving-ease sires was associated with lower calf birthweights and dystocia rates but similar weaning rates. Heifers that attempted to deliver calves with greater than the calculated Predicted Deliverable Pounds (PDP), when compared with deliveries where the calves were the same to 10 lbs less, 11 to 20 lbs less, or more than 20 lbs less, experienced higher rates of dystocia (calving-ease scores of 1.82, 1.23, 1.07, and 1.11; p < 0.05). Knowing the pelvic area (PA) and PDP did not provide a reliable prediction of which heifers would experience dystocia. Practitioners recommending artificial insemination programs should expect differences in results. This report suggests average results that might be expected.