Factors Influencing Growth of Ayrshire Bulls Tested at Station

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Abstract
Data on 385 Ayrshire bulls tested at station were analysed to study the effect of 39 external variables concerning the bull, its dam, herd of birth and sire on 10 growth traits. Birth year-season subclass had a significant effect on all growth traits. Average daily gain in the testing period (from 60 to 365 days of age) was poorest for bulls born in the spring. Estimates of heritability for total gain and final weight were of the order of 0.30. An increase in a bull's birth weight resulted also in increased average daily gain in the testing period. Variability for daily gain in the period from 270 to 365 days of age was large implying that substantial differences existed in the growth pattern of bulls at this age.