A Comparison of Six Protein Quality Assays Using Commercially Available Protein Meals , ,

Abstract

The protein quality of 20 commercially available animal by-product meals (9 meat and bone meals, 6 feather meals, 3 fish meals, and 2 hair meals) was evaluated using chick protein efficiency ratio (PER), net protein utilization (NPU), pepsin digestibility, Tetrahymena furgasoni bioassay, dye-binding, and chemical score. The first limiting amino acid(s) in the animal proteins for chick weight gain were the total sulfur amino acids (TSAA) for both meat and bone meal and fish meals; however, methionine was the first limiting amino acid for the keratin proteins, feather, and hair meals. Each protein quality test produced different rankings for the animal proteins; however, the correlation coefficients between PER and NPU, relative nutrient value (RNV), pepsin digestibility, dye-binding, and chemical score were r = .922, .856, .910, .628, and .883, respectively, for the 20 animal proteins. The pepsin digestibility values correlated the highest with the chick growth assays, (PER and (NPU) suggesting the pepsin test may be a quick reliable method to evaluate protein quality in animal by-products.