PREWEANING PATTERNS OF GROWTH IN THREE BREED GROUPS OF ANGE BEEF CALVES

Abstract

Preweaning weight records of 2856 spring-born calves raised at the University of Alberta cattle ranch during a 15-yr period were used in this study. Calving occurred mainly in April and May every year. Calves from three breed groups: Hereford (HE), Beef Synthetic (SY) and Beef Crossbred (XB) were weighed at birth, and in late June, July and August and at weaning in mid-October. They were classified as early, mid-season and late-born according to their birth dates. Average daily gain (ADG) between two consecutive weighings and relative growth rate (RGR) at each interval were analyzed by the least squares method and the adjusted means were plotted against the mean ages of the calves classified at 2-wk intervals to determine the pattern of changes in ADG and RGR with the increase in age of the calf. The SY calves had the highest ADG and RGR followed by the XB and HE (P < 0.05). Bull calves exhibited significantly higher (P < 0.05) absolute growth rate than heifer calves but the sexes were not different in RGR. Preweaning ADG reached a peak when calves were between 110 and 120 d old and declined thereafter. The decline in RGR was linear during the preweaning period. The mean growth rates of the early and mid-season calves were significantly (P < 0.05) higher than that of the late-born calves, and early-born calves showed more consistent gain than the mid-season and late-born calves. A pronounced decline in gain was observed for mid-season and late-born calves in late summer when pasture condition deteriorated indicating that early weaning and supplementation of calves' diet at that stage might be beneficial in sustaining growth rate of the calves. Key words: Cattle (beef), preweaning growth, calf (beef)