The use ofn‐paraffin‐grown yeast as the main source of protein in diets for chicks

Abstract

1. n‐Paraffin‐grown yeast and a mixture of soyabean meal and fish meal were compared in the net protein utilisation (NPU) test, and as protein supplements in diets for broilers up to 4 weeks of age. 2. The difference between the NPU values, 0.66 for yeast and 0.80 for the soyabean meal and fish meal mixture, could largely be attributed to the high nucleic acid content of the yeast. 3. Chicks given the diet containing yeast (190 g/kg) did not grow as rapidly as those given the soyabean meal and fish meal reference diet, and the reduced growth could only partly be explained by a marginal deficiency of methionine. 4. Food conversion efficiency with the yeast diet was improved by maize oil while responses to α‐tocopheryl acetate and sodium selenite were inconsistent. 5. Chicks grew well when yeast replaced fish meal in the mixture of soyabean meal and fish meal, and when fish meal (194 g/kg diet) was the sole protein supplement.