COMPARATIVE GROWTH RATES OF SHORTHORN AND CROSSBRED BEEF CALVES FROM BIRTH TO 1 YEAR OF AGE

During the 3 years 1959, 1960, and 1961 the purebred Shorthorn herds at the Experimental Farms at Ottawa, Lennoxville, and Kapuskasing were randomly bred to Shorthorn, Angus, Hereford, and Charolais bulls. Three bulls per breed were used each year. Birth weights and rate of gain from birth to 1 year of age were measured in the 254 calves produced. Breed of sire, sex, year of birth, and age of dam were found to be significant sources of variation contributing to weight at birth, but only breed of sire was a significant source of variation in the rate of gain from birth to 1 year of age. Charolais-sired calves were heaviest at all ages, and Hereford next heaviest at all ages. Angus-sired calves were lightest at birth two years of three, but at weaning they were heavier than the purebred Shorthorn calves. The purebred Shorthorns were lightest at weaning and at 1 year of age.

GROWTH RELATIONSHIPS FROM BIRTH TO 240 DAYS OF AGE AND THEIR ASSOCIATIONS WITH FEED EFFICIENCYIN DAIRY CALVES

Weights at birth, 180 days, and 240 days of age as well as the gains and live weights from birth to 180 days and from 180 to 240 days on Jersey, Ayrshire and Holstein heifer calves were utilized in an attempt to predict pounds of TDN required per pound of gain during the interval 180 to 240 days. The variable most highly associated with feed efficiency was the gain from 180 to 240 days, and the simple regression indicated that 60 to 75 per cent of the variation in feed efficiency could thus be accounted for. The regression coefficient was of the order of −0.05 for the Jersey and the Holstein, and −0.06 for the Ayrshire. The other variables considered did not increase the accuracy of the simple regression equation in the prediction of feed efficiency.