Calving date prediction based on transrectal ultrasonography determination of gestational age in beef cattle

Abstract

In cattle, accurate gestation length determination during pregnancy diagnosis helps to determine calving date. This aids beef cattle producers to estimate length of calving season, labor availability and labor cost and to make nutritional management decisions. The objective of the study was to determine the error rates for projected calving date based on ultrasound determined gestational age in comparison to actual gestational age (derived as the number of days from artificial insemination [AI] date). Reproductive tract ultrasound examinations were performed in 8887 Angus cross beef females that were artificially inseminated in 12 spring calving herds between 2011 and 2016 to determine gestational age of the embryo or fetus. Only pregnancies estimated to be between 30 and 120 days (n = 6355 heifers and n = 2532 cows) were used in this study. The projected calving dates for actual and ultrasonography based gestational ages were determined using gestational length for beef cattle breed. Actual calving date, number of calves delivered at birth, gender of calf born, calf weight, and incidence of assisted birth were recorded. In heifers, the error rates for calving date prediction for actual and ultrasonography gestational ages were 22.1 and 9.9% respectively (P<0.0001); whereas in cows the error rates for actual and ultrasonography gestational ages were 13.5 and 9.1% respectively (P<0.01). The results of the multivariate analysis revealed dam’s age and sire’s calving ease estimated progeny difference (EPD) score influenced the accuracy of calving date prediction based on ultrasound determined gestational age (P<0.01). In conclusion, ultrasound determination of calving prediction was more accurate than traditional breeding date based calving prediction.