Estimation of calving date in beef cattle with real-time ultrasound

The objective of this study was to evaluate the accuracy of predicting calving date using real-time ultrasound and determine factors that may increase accuracy. Ultrasonic scanning was performed on 207 Angus and 771 Angus × Simmental beef cows and heifers using a 5-MHz linear rectal transducer. Ultrasonic scanning was conducted 32 to 110 d of gestation. Calving date was recorded for 773 of the 978 cattle. Ultrasonic scanning was performed under field conditions, with the first image of crown rump (n = 18), head biparietal (n = 241), head length (n = 28), or trunk diameter (n = 486) frozen and measured for a total of 773 measurements. Regression analysis was performed for each measurement using calving date. The regression SE for crown rump, head biparietal, head length, and trunk diameter was 5.79, 8.75, 6.11, and 7.81, respectively. Multivariate regression determined breed, sire, sex, and first parity influenced the calving date prediction. Bias analysis was performed to compare regression lines from prior studies. Calving date was predicted within ±15 d with ultrasonic scanning in the present study.