Date of this Version
Growth records of 504 pedigree selected Holstein-Friesian bulls by 120 sires collected for progeny testing at the American Breeders Service, Inc., DeForest, Wisconsin from 1964 to 1971, were studied to determine the shape of the growth curve, relationships among body weights and growth rates at various ages and to estimate heritability of growth. Body weight and average/daily gain were consistently higher than the previous growth standards for Holstein-Friesian bulls. Bulls weighed about 480 kg at 15 months, which was 46% of average mature weight. Average daily gain ranged from 1.3 to 0.8 kg between 6 and 18 months of age. A sustained high rate of gain was observed even beyond recommended slaughter age which clearly shows that Holstein-Friesian bulls with potentially high milk production levels also have a good capacity to produce beef. Body weights, expressed as deviations from contemporary group averages, at successive ages were positively correlated but the relationships declined as intervals between ages increased, indicating that using earlier weights to predict later weights would be effective only at shorter age intervals. There were no definite relationships between growth rates at subsequent ages, implying that growth rates obtained for a certain age range should be applied only for that particular age range. Correlations between body weight and growth rates were largely negative, suggesting that heavier animals at certain ages tended to gain less in subsequent periods. Within group heritabilities for body weight increased with age from 6 to 30 months of age but gradually declined thereafter. The trends for average daily gain (ADG) and daily gain per 100 kg body weight (DG/100) were almost the opposite for body weight. The overall average heritability estimates for body weight, ADG and DG/100 were 0.83, 0.44 and 0.46, respectively. Since the majority of the Holstein-Friesians being born are progeny of AI sires, the values for growth rate will serve as a standard for Holstein-Friesian males.