FEED INTAKE OF GROWING BULLS DURING SEVERE WINTERS

Abstract

Dry matter (DM) intake was recorded daily for 12 pens of young bulls for 140 d in each of eight winters. Monthly means for DM intake ranged from 1.94 to 2.62 kg 100 kg−1 body weight (BW) and average daily gains (ADG) ranged from 1.15 to 1.46 kg d−1. Stepwise multi-variable procedures indicated that days on test (age) accounted for most of the variation in feed intake (partial R2 = 0.380). Climatic variables provided little additional explanation. Dry matter intake was scaled to 100 kg BW to minimize the influence of increasing weight with time. The multi-variable model which described weight-scaled DM intake included age (partial R2 = 0.509) and daily temperature (partial R2 = 0.013). Weight-scaled intake declined with age; the temperature effect represented a 2% increase in response to a drop in temperature from 0 to −15 °C. Equivalent increases in weight-scaled DM intake of 4.5 and 6.5%, respectively, were calculated by simple linear regressions based on daily or monthly temperature and intake values. Temperatures below −20 °C had no greater effect on intake or weight-scaled intake than those in the −10 to −20 °C range. It was also concluded that silage was unlikely to reduce DM intake at low temperatures and that European breeds of bulls had a twofold greater (P < 0.01) increase in weight-scaled DM intake in response to cold than did British breeds. Key words: Cattle, cold, environment, feed intake, winter