EVALUATION OF MILK VARIABLES AS MEASURES OF MILK EFFECT ON PREWEANING PERFORMANCE OF BEEF CATTLE

Abstract

A study with 176 (1966) and 201 (1967) cows from the University of Alberta beef herd was conducted to investigate the effectiveness of a number of milk variables for explaining variance in preweaning gain of beef calves. The seven milk variables calculated over 24 hours were yield of milk, total energy, total protein and total solids, and percentages of butterfat, protein and solids-not-fat. These variables were measured for two periods, August and October, and averages for the two periods were calculated. Mean 24-hour milk yield ranged from 3.8 to 6.1 kilograms. Percentage of butterfat, protein and solids-not-fat, respectively, ranged from 4.10 to 5.77, 3.28 to 3.93, and 8.67 to 9.50. The intercorrelations among yield of milk, energy, protein and total solids were high and positive, ranging between 0.85 and 0.99. Correlations of milk yield with percent milk components were small and predominantly negative. Intercorrelations of percent milk components ranged from 0.09 to 0.55. Correlations of mean milk yield variables and average daily gain (ADG) of calf to weaning for the two periods ranged from 0.73 to 0.78. In most instances, total milk yield was equally or more highly correlated with ADG than the other milk yield variables. Correlations of percent milk components with ADG were low, and in most instances not significant. In 1966 data, little additional variation in ADG was explained by the inclusion of other milk variables over that explained by milk yield alone. In 1967, the inclusion of milk percent components accounted for from 2 to 7% of variance in ADG over milk yield alone. Average milk yield for the two periods of milking was more consistent than a single milking in explaining variance in ADG over both years. The response of ADG of calf to milk yield was essentially a linear relationship, but there were indications that the curvilinear relationship of ADG and milk yield should not be ignored in beef herds of relatively high milk production.