Standardized Ileal Amino Acid Digestibilities of Sorghums from Different Sources in Yellow-Feathered Chickens and...

Prediction models for standardized ileal amino acid digestibilities (SIAADs) of sorghums in yellow-feathered chickens have not been previously reported. This study characterized the chemical composition of 10 sorghum samples from different sources, assessed their SIAADs in medium-growing yellow-feathered chickens, and subsequently developed and validated prediction models based on chemical composition and amino acid profiles. A total of 276 Tianluma roosters (60 d of age) were randomly assigned by body weight (average 1.32 kg per bird) to 11 dietary treatments, including a nitrogen-free diet (NFD) group and 10 sorghum-based diet groups. Each treatment included 6 replicate cages, with 4 birds per replicate cage for the sorghum-based diet groups and 6 birds per replicate cage for the NFD. Birds were fed the experimental diets from d 63 to 67, after which ileal digesta were collected to determine SIAADs of 10 sorghum samples. Data from 9 sorghum samples were used to establish prediction equations using stepwise regression, while the remaining sample was used for model validation. Sorghum source significantly influenced (p ≤ 0.002) the SIAADs of most amino acids. Arginine (Arg) exhibited the highest standardized ileal digestibility (SID) (68.2%), whereas tyrosine (Tyr) showed the lowest value (49.0%). Eighteen preliminary prediction models were developed for the SIDs of valine (Val, R² = 0.981, p = 0.001), methionine (Met, R² = 0.978, p < 0.001), isoleucine (Ile, R² = 0.983, p < 0.001), leucine (Leu, R² = 0.981, p < 0.001), threonine (Thr, R² = 0.748, p = 0.016), phenylalanine (Phe, R² = 0.981, p < 0.001), lysine (Lys, R² = 0.988, p < 0.001), histidine (His, R² = 0.988, p = 0.004), Arg (R² = 0.986, p < 0.001), tryptophan (Trp, R² = 0.934, p < 0.001), aspartic acid (Asp, R² = 0.986, p < 0.001), serine (Ser, R² = 0.980, p < 0.001), glutamic acid (Glu, R² = 0.988, p < 0.001), glycine (Gly, R² = 0.898, p = 0.007), alanine (Ala, R² = 0.983, p < 0.001), cysteine (Cys, R² = 0.968, p = 0.003), Tyr (R² = 0.898, p = 0.001), and proline (Pro, R² = 0.944, p = 0.002). The models for the SIDs of Lys, His, and Glu exhibited the highest coefficients of determination (R² = 0.988, p ≤ 0.004), whereas the model for the Thr SID exhibited the lowest fit (R² = 0.748, p = 0.016). Except for Leu and Tyr, the predicted values of the remaining amino acids were generally consistent with the determined values in the validation sample. These preliminary models provide a basis for estimating amino acid digestibilities in sorghums for medium-growing yellow-feathered chickens.