Comparison of amino acid digestibility coefficients for corn, corn gluten meal, and corn distillers dried grains with solubles among 3 different bioassays

The objective of this study was to determine standardized AA digestibility of corn, corn gluten meal, and 3 distillers dried grains with solubles (DDGS) using the precision-fed cecectomized rooster assay (PFR), the standardized ileal AA broiler chicken assay (SIAAD), and a newly developed precision-fed ileal broiler chicken assay (PFC). For the PFR, cecectomized roosters were precision-fed approximately 30 g of feed sample, and excreta were collected 48 h postfeeding. For the SIAAD, 16-d-old broilers were ad libitum fed a semi-purified diet containing the feed samples as the sole source of protein from 17 to 21 d, with ileal digesta collected at 21 d. For the PFC, 22-d-old broiler chickens were precision-fed 10 g of feed and ileal digesta were collected at 4 h postfeeding. For corn, the PFC yielded significantly higher digestibilities than the SIAAD and PFR for several AA. For corn gluten meal, the PFR yielded significantly higher values than the PFC for the majority of the AA, with the SIAAD yielding intermediate values. When 3 DDGS samples were evaluated, the PFR produced higher digestibilities than the PFC for all 3 DDGS samples for most of the AA. When comparing the PFR and the SIAAD, the PFR yielded higher values than the SIAAD for one DDGS, whereas there was generally no significant difference between these 2 methods for the other 2 DDGS samples. The results of this study indicate there were differences among standardized AA digestibility values for the PFR, SIAAD, and PFC in some instances. The differences among methods were not consistent; however, the PFR yielded higher digestibility values than the PFC for 4 of the 5 ingredient samples.