Relationship of Body Measurements, Weight, Age and Fatness to Size and Performance in Beef Cattle

Abstract

Data on 318 Hereford and 516 Angus cows and their progeny were studied for the effects of cow weight, cow wither height, cow fat thickness, calf fat thickness and cow size and shape indexes on 205-day weaning weight, adjusted wither height and principal component size and shape indexes of calves. Principal component analysis was used as a method of defining animal size and shape. The first component for both cows and calves contrasted animals according to general size and accounted for 56.2 and 46.9% of the variation in the correlation matrices for cows and calves, respectively. The second component contrasted animals according to body shape. Total variation explained by the first two principal components was 72.5 and 67.2% for cows and calves, respectively. Stepwise multiple regression analysis indicated that calf fat thickness and cow weight were the most important effects on calf 205-day weaning weight. Variables exhibiting the most important effects on calf wither height were calf fat thickness and cow wither height. Coefficients of determination (R2) for calf weight and wither height were 10.7 and 6.5%, respectively. Variables with the greatest effect on calf size index were calf fat thickness, cow weight and cow shape index. Calf fat thickness and cow height were significant effects in the equation describing the regression of calf shape index on the cow variables. Coefficients of determination from analyses of calf size and shape indexes were 26.7 and 8.9%, respectively.