An Evaluation of the Protein Quality of Various Protein Sources from Chicken, Whey, and Soy Concentrates Commonly Used in Pet Diets and Select Human Performance Foods

The objective of this experiment was to evaluate protein utilization and nutrient composition of various animal and vegetable proteins used in pet food manufacturing. All protein sources were analyzed for proximate, amino acid, and mineral composition. Experimental protein sources included spray dried egg (SDEG), and 4 spray dried chicken samples varying by process conditions (SDLF, SDLF1, SDLF2, and PDC), low temp and pressure fluid bed dried chicken (LTPC), powdered chicken broth (PCB), pea protein concentrate (PPCO), pea protein isolate (PPIS), soy protein concentrate (SPCO), soy protein isolate (SPIS), 2 whey protein concentrates (WPCO and WPCOA from previous experiment), and 2 whey protein isolates (WPIS and WPISA from previous experiment) were added to a nitrogen free basal diet to contribute 10% crude protein. The nitrogen free basal diet was used as a negative control while the SDEG was the positive control. Day old male broiler chicks (Cobb*Cobb) were allowed a 7-day acclimation period and fed a starter diet and water ad libitum. The experimental unit was pen containing 5 broiler chicks each.  Experimental diets were fed for 10 days with weights and feed intake recorded. The experiment was approved by the KSU IACUC. Differences in treatment were analyzed using the GLIMMIX procedure in SAS (v9.4). Protein efficiency ratio (PER) was calculated as weight gain per unit of protein intake. The PER of SDEG was 4.50 and was similar to SDLF, SDLF1, SDLF2, and PDC were 4.04, 3.96, 4.22, and 4.56, respectively. The PCB, PPCO, PPIS, SPCO, SPIS, WPCO, WPCOA, WPIS, and WPISA had much lower (P<0.0001) PER values of -1.82, -1.06, -0.32, 2.19, 1.65, -1.47, -2.55, -4.38, and -6.98, respectively. The negative PER values indicate that the birds lost weight when fed these protein sources due to critical limitations of one or more amino acids. Overall this work suggests that broiler chicks, as a model, work well when evaluating processing differences among protein sources of poultry origin; but, severely penalize plant and dairy protein sources and might not be the appropriate model when exploring process modifications in these non-poultry ingredients for use in pet food applications.