Amino acid availability values for several protein sources for yellowtail ( Seriola quinqueradiata)

Abstract

Amino acid availability and protein digestibility values for brown fish meal, casein, meat meal, soy protein concentrate, corn gluten meal and full-fat soybean meal were determined in yellowtail. These proteins were incorporated at 40–72% of the diet as the only source of protein to yield 30–36% crude protein diets. The apparent average amino acid availability and apparent protein digestibility values were similar: 89.3 and 88.7%, 96.7 and 95.4%, 78.4 and 80.3%, 87.5 and 87.3%, 46.8 and 49.7%, 78.1 and 83.2% for brown fish meal, casein, meat meal, soy protein concentrate, corn gluten meal and full-fat soybean meal, respectively. True average amino acid availability and true protein digestibility values were also similar: 92.7 and 94.2%, 100.0 and 99.0%, 82.0 and 85.7%, 90.8 and 92.9%, 50.9 and 55.1%, 82.4 and 90.2%. All essential amino acid availability values were not significantly different from comparable values based on protein digestibility data ( P < 0.05) except for histidine in full-fat soybean meal. Protein digestibility values can be used to approximate available amino acid values in diets. However, precaution should be taken because some amino acids may have lower availability than predicted based on protein digestibility values, such as histidine in full-fat soybean meal found in the present study.