Body Size of Calves from Holstein Dams and Sired by Holstein or Angus Bulls

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Abstract
The influence of breed of sire on birth size of calves was determined from measurements on 687 calves from Holstein dams. Ten Holsteins sired 491 (H-H) calves that averaged 93 lb, 308 in heart girth, and 5.1 in maximum width of head. Four Angus sired 196 (A-H) calves with comparable averages of 79 lb, 29.3 in, and 5.0 in, respectively. Analysis of covariance, adjusting size of calf for size of dam, revealed that H-H calves were significantly larger in body weight, heart girth, and head width than calves sired by Angus bulls (P< 0.01). Two Holstein bulls sired significantly larger calves than the other eight Holsteins and one Angus bull sired significantly smaller calves than the other 3 Angus. The average length of gestation was significantly different between breeds and between bulls within breeds (P < 0.01). Gestation length, age, and size of dam were significantly correlated with size of calves (P<0.01) but these coefficients were too small to be of much value in predicting birth size of calves. Calving difficulties occurred in 26 births, but the incidence (1.5% for A-H calves and 4.7% for H-H calves) seemed rather low and could not be attributed to particular sires within breeds.