The protein requirement of the ruminant calf. II. Further studies on the effect of protein content of the concentrate mixture on the performance of calves weaned at an early age

Abstract

1. Eighty-four Friesian heifer calves were used in two experiments (Experiments 4 and 5) to study the protein requirement of the ruminant calf to 12 weeks of age. The calves were weaned at 5 weeks of age and given a concentrate containing one of several protein levels, together with hay and water.2. In Experiment 4, the effect of changing the protein content of the concentrates at 8 weeks of age under ad libitum feeding conditions was studied. A concentrate containing 20·6% crude protein (air-dry basis) tended to promote more rapid weight gains in calves to 8 weeks than a similar concentrate with 12·1% crude protein. Following the change in diet at 8 weeks, both groups of calves given the low-protein diet gained weight at similar rates in the period 8–12 weeks, irrespective of the protein level to 8 weeks. During the period 8–12 weeks calves given the high-protein diet, after receiving a low-protein diet to 8 weeks, tended to gain weight at a faster rate than those given the high-protein concentrate throughout. After adjustment for differences between treatment groups in mean concentrate consumption and mean live-weight at 8 weeks, the live-weight gain from 8 to 12 weeks was significantly greater in calves given the high-protein diet after 8 weeks.3. In Experiment 5, a significantly lower growth rate was obtained when concentrate intake was restricted to a maximum of 2 kg./day than when given ad libitum. Calves given the concentrates containing 15·9% or 20·6% crude protein gained weight significantly faster than those given the concentrate containing 12·1% crude protein, at both levels of feeding, after live-weight gain was adjusted for differences between treatment groups in mean food consumption and live-weight at 1 week.4. It is concluded that no advantage is obtained by giving a concentrate containing more than 15·9% protein to Friesian heifer calves weaned at 5 weeks of age. The results indicate clearly the importance of an adequate supply of energy in the diet of the ruminant calf if maximum live-weight gain is to be achieved.