The nutrition of the early-weaned calf III. Protein solubility and amino acid composition as factors affecting protein utilisation

Abstract

SUMMARY1. Nitrogen balance studies have been conducted on 16 early-weaned calves given four diets containing groundnut meal or herring meal, the protein of which had been rendered soluble or insoluble by different methods processing.2. There were highly significant differences in nitrogen retention between ‘soluble’ and ‘insoluble’ herring meals but no differences between ‘soluble’ ‘insoluble’ groundnut meals.3. ‘Insoluble’ herring meal gave retention values which tended to be higher (significantly so, in one experiment), and ‘soluble’ herring meal gave values significantly lower, than either type of groundnut meal. Mean daily live-weight gains tended to follow the same pattern.4. Blood-urea concentration was significantly lower on the diets containing herring meal than on those containing groundnut meal but within each type meal did not differ according to solubility.5. These results are discussed in the light of in vitro studies on the effect of pH on protein solubility.6. It is concluded that solubility is of minor importance in groundnut meals but of major importance in fish meals when these are included in early weaning diets for calves.7. Under conditions of low or ‘potentially low’ solubility the amino acid content of the protein source appears to be of considerable significance.