127 - Standardized Amino Acid Digestibility and Protein Quality of Extruded Canine Diets Containing Hydrolyzed Protein

Abstract: Hydrolyzed protein in companion animal diets has been of public interest because of itsdecreased susceptibility to elicit overreacting immune response and the potentially easier digestion. Thus, the objective of this study is to determine the chemical composition, standardized amino acid digestibility, and protein quality of 2 test protein hydrolysates, chicken liver hydrolysate (CLH) and chicken hydrolysate (CH), compared with a traditional chicken meal low ash (CM) in extruded canine diets. Five treatment diets were formulated to have similar ingredient compositions except for the main protein source, 1) CONd: CM diet; 2) 5%CLHd: 5% substitution of CLH of CM diet; 3) CLHd: CLH diet; 4) 5%CHd: 5% substitution of CH of CM diet; 5) CHd: CH diet. A precision-fed rooster assay using cecectomized roosters (n=4/treatment) was conducted to determine the standardized amino acid ileal digestibility and Digestible Indispensable Amino Acid Score (DIAAS) like values for the 3 protein ingredients and 5 extruded diets. The standardized ileal digestibility for the 10 indispensable amino acids was all equal or greatere than 80% in all protein sources and treatment diets. Tryptophan digestibility in 5%CLHd was less than CLHd (P < 0.05) but no difference was seen when compared with the other diets (P > 0.05). The DIAAS-like values of the diets according to AAFCO nutrient profile showed that tryptophan was the first limiting amino acid for CONd, 5%CLHd, and 5%CHd; the diets containing only protein hydrolysates had no limiting amino acid as their DIAAS-like values were greater than 100%. The DIAAS-like values were less in CONd (95.6%), 5%CLHd (94.9%), and 5%CHd (96.2%) compared with CLHd (104.5%) and CHd (116.9%) (P < 0.05). In conclusion, all test protein sources were well digested; however, substituting CM with protein hydrolysate could increase protein quality in canine extruded diets.