Prediction of the concentration of standardized ileal digestible amino acids in distillers dried grains with solubles for poultry: A meta-analysisr Poultry: A Meta-Analysis

High variability in amino acid (AA) content and digestibility among sources of corn and wheat distillers dried grains with solubles (DDGS) creates challenges for nutritionists when using it in precision nutrition feeding programs. A meta-analysis based on 86 observations from 19 publications was conducted to develop equations for predicting standardized ileal digestible content (SIDC) of AA based on variable chemical composition among DDGS sources (75 corn DDGS, 9 wheat DDGS, 1 wheat-corn DDGS blend, and 1 undefined DDGS source). A mixed model was used to develop prediction equations for SIDC of AA, and a backward selection of variables was conducted based on chemical composition of DDGS sources. Crude protein, NDF, and ADF content were greater (P < 0.05) in wheat-DDGS than in corn-DDGS. Wheat DDGS had greater (P < 0.05) concentrations of Arg, His, Ile, Phe, Thr, Trp, and Val, but less (P < 0.05) Leu content than corn-DDGS. The standardized ileal digestibility (SID) of AA in DDGS from all sources ranged from 61.9% (Lys) to 84.5% (Trp). Except for Phe, all indispensable AA had different SID between corn- and wheat-DDGS (P < 0.01). The AA content in DDGS source was the best predictor of SIDC for all AA. The prediction equations for SIDC of Met, Lys, Thr, and Trp were: y(%) = - 0.12 + 1.05 × Met (%, R² = 0.90), y(%) = - 0.22 + 0.91 × Lys (%, R² = 0.87), y(%) = - 0.17 + 0.88 × Thr (%, R² = 0.84), and y(%) = - 0.03 + 1.00 × Trp (%, R² = 0.99), respectively. Prediction equations were developed for SIDC of Met and Lys using data from broiler chick assays (y(%) = - 0.16 + 1.12 × Met(%) and y(%) = - 0.24 + 0.90 × Lys(%), respectively), and rooster assays (y(%) = - 0.05 + 0.97× Met(%) and y(%) = - 0.20 + 0.97 × Lys(%), respectively). For all the prediction equations, the intercept (= 0) and slope (= 1) were not different between predicted and observed SID AA values, indicating high accuracy of the models. In conclusion, equations for predicting SIDC of AA in DDGS were developed and showed that total AA concentration was the best predictor of SIDC. These prediction equations can be used by animal nutritionists to more accurately estimate SIDC of AA among DDGS sources in diet formulations for precision poultry nutrition feeding programs.