Standardized Ileal Amino Acid Digestibilities in Different Corn Sources for Medium-Growing Yellow-Feathered Broilers and Their Prediction Models

The present study first aimed to analyze the chemical compositions and amino acid (AA) profiles in 10 different sources of corn samples, then determine the SIAADs of these corn samples in medium-growing yellow-feathered broilers and establish rapid prediction equations for SIAADs based on their chemical compositions and AA profiles, and finally preliminarily assess their predictive performance. Broilers (n = 276; medium-growing yellow-feathered broilers; 63 days of age) were randomly allocated to 11 dietary treatments based on initial body weight. The experimental groups consisted of one nitrogen-free diet (NFD) control and 10 corn diet groups, and each experimental group consisted of 6 replicates, with 6 chickens per replicate in the control group and 4 chickens per replicate in each corn diet group. The experimental period was 5 days. At 67 days of age, ileal digesta samples were collected. Both apparent ileal amino acid digestibilities (AIAADs) and SIAADs in corn were evaluated. Predictive equations for corn SIAAD values were constructed via stepwise regression based on 9 corn samples. One independent corn sample was randomly selected to provide a preliminary assessment of predictive performance of the SIAAD models. The results showed that corn sources affected (p < 0.05) the AIAADs and SIAADs in yellow-feathered broilers. Among all assayed AAs, leucine (Leu) showed the highest apparent ileal digestibility (AID) (84.9%) and tryptophan (Trp) the lowest (52.8%), whereas glutamic acid (Glu) demonstrated the highest standardized ileal digestibility (SID) (94.6%) and Trp the lowest (64.5%). Equations predicting SID values for 6 AAs, including methionine (Met), phenylalanine (Phe), histidine (His), Trp, Glu, and proline (Pro), in corn samples for yellow-feathered broilers were constructed (R2 = 0.559 to 0.883, p ≤ 0.021). Among the established prediction models, the model for the SID of Trp showed the best fit (R2 = 0.883, p < 0.002), whereas the model for His SID showed the weakest goodness of fit (R2 = 0.559, p = 0.021). Except for the SID prediction model for Trp, which showed poor predictive accuracy, the other 5 SIAAD prediction models provided preliminary evidence supporting the potential applicability of these models. Therefore, these established prediction equations can provide an important reference for the rapid prediction of the SIDs of these AAs in corn samples for medium-growing yellow-feathered broilers in the future. Owing to the small sample size in this study, further independent external validation is necessary to verify the accuracy of the derived SIAAD prediction equations.