Protein Nutritive Quality of Commercial Fish Meals as Assessed by Biological and Chemical Methods

Various chemical characteristics of fish meals pertaining to the protein and lipid components were determined and their relation to different biological estimates of protein quality were studied. The results demonstrated the practical importance of selecting appropriate biological assays in order to avoid underestimating or overestimating protein quality. Pepsin digestibility of the crude protein remaining in the meals after chloroform–methanol extraction was significantly correlated with biological estimates of protein quality. Meals of initially high supplementary protein value declined in value to a greater extent than did meals of lower quality. The level of available lysine present in the meals declined with storage but biological tests indicated that a combination of several amino acids rather than any single amino acid was limiting to supplementary protein value.