Chemical composition and protein digestibility of poultry by-product meals for salmonid diets

Poultry by-product meal (PBM) is a potential substitute for a portion of the fish meal typically used in salmonid feeds. The nutritional value of commercial PBM as a fish meal replacement will depend primarily upon the quality and quantity of protein in a particular PBM batch. The purposes of this study were to quantitate the chemical variability in samples of PBM obtained from several manufacturers in North America, and to determine the digestibility of PBM protein by salmonids using one in vivo and three in vitro methods. The range in dry weight proximate composition among PBM samples was 55–74% for protein, 10–19% for lipid, and 11–23% for ash. Of the three in vitro methods for predicting in vivo protein digestibility, a method using trout pyloric ceca enzymes was the most sensitive and was more closely correlated to in vivo results than the other in vitro methods examined. We found significant differences in chemical composition and protein digestibility of PBM samples obtained from different manufacturers, illustrating the range of protein quality in PBM products that fish feed manufacturers will encounter in the marketplace.