PSXIII-27 - Evaluation of protein quality of select chicken-based protein sources using the precision-fed cecectomized rooster assay

Abstract: The objective of this experiment was to determine and compare the standardized amino acid (AA) digestibility of chicken-based protein sources using the precision-fed cecectomized rooster assay. Four ingredients were tested: spray-dried chicken protein hydrolysate (CPH), spray-dried chicken meat (CC), spray-dried chicken broth (CB), and chicken meal (CM). All animal care procedures were approved by the University of Illinois Institutional Animal Care and Use Committee prior to experimentation. Sixteen cecectomized roosters (4 roosters per substrate) were randomly assigned to the four test substrates. After 24h of feed withdrawal, roosters were tube-fed 12g of test substrates and 12g of corn. Following crop intubation, excreta (urine and feces) were collected for 48h. Endogenous corrections for AA were made using 5 additional cecectomized roosters. All data were analyzed using the Mixed Models procedure of SAS version 9.4. Generally, CC had the highest (P < 0.05) standardized digestibility for AA, followed by CPH. Methionine, phenylalanine, and valine had higher (P < 0.05) digestibility in CC and CPH compared to CB and CM. Digestibility of isoleucine and leucine were higher (P < 0.05) in roosters fed CC, followed by CPH, CM, and CB. Higher digestibility (P < 0.05) of lysine was observed in rooster fed CC and CPH, followed by CM and CB. Histidine and threonine had the lowest digestibility (P < 0.05) in CB compared to all other ingredients. In contrast, digestibility of tryptophan was highest (P < 0.05) in CC, followed by CPH and CB, while CM had similar (P >0.05) digestibility to CC and CPH. Amino acid digestibility for most indispensable AA was above 80% for all ingredients, except for histidine, lysine, and threonine, which were exceptions only for CB (68%, 73%, and 74%, respectively). For selected dispensable AA, amino acid digestibility was above 60% for all ingredients, except for aspartic acid in CB and CM, and serine in CB, which were exceptions (43, 68% and 66%, respectively). In general, the lowest DIAAS values were observed in roosters fed CB, followed by CPH, CM, and highest in CC. Overall, CC and CPH have comparable indispensable AA digestibility, and tryptophan or phenylalanine+tyrosine were, generally, the first limiting AA.