Composition and protein fractions of different meat by-products used for petfood compared with mechanically separated chicken (MSC).

Pork by-products (lung lobes, kidneys), chicken viscera (head, feet and viscera) and mechanically separated chicken (MSC) were evaluated for proximate composition, protein distribution and connective tissue. Proximate composition varied among meat by-products and MSC. Pork by-products contained the most crude protein (p<0.05). Low levels of high ionic strength soluble (HIS) proteins were obtained from meat by-products. Pork lungs and chicken viscera contained the greatest amounts of insoluble (IN) proteins (p<0.05). Total collagen values were positively correlated to IN proteins, intramuscular collagen (IMC) and elastin. Types I and III collagen could not be detected by SDS-PAGE for the different meat by-products though collagen solubility appeared to be significant. These results suggest functional property differences between specific by-products are likely when used in petfood product formulations.