Amino Acid Limitations of Yeast Single-Cell Protein for Growing Chickens1

ABSTRACT Four experiments were conducted to determine the amino acid limitations of yeast single-cell protein (YSCP) when fed as the only source of protein in semipurified diets for broiler chicks. The results of two experiments showed that methionine and arginine were the first and second most limiting amino acids, respectively, in YSCP for chick growth and feed efficiency. On a calculated basis, YSCP seemed to be deficient in leucine, but leucine supplementation of YSCP diets did not improve chick performance. Weight gain and feed efficiency of chicks fed YSCP diets supplemented with amino acids were inferior to those of chicks fed diets in which soy protein was used. When feed intake was equalized by pair-feeding the soy protein diet with the amino acid supplemented-YSCP diet, chick performance was similar irrespective of protein source. Also, the use of a granular form of YSCP in diets improved chick performance as compared with the use of YSCP in powder form. Data obtained from this research show that methionine and arginine are the most limiting amino acids in the YSCP tested. Also, these data suggest that, when the palatability factor associated with YSCP is alleviated and proper amino acid supplementation is used, YSCP can be fed successfully as the sole source of protein in semipurified diets for chicks. (Key words: yeast, protein, amino acids, broilers) 1982 Poultry Science61:337-34