Determination and prediction of standardized ileal amino acid digestibility of wheat for pullets during the brooding and growing phases

Wheat serves as a major alternative to corn in layer diets. However, the assessment and predictive models for standardized ileal digestibility of amino acids (SIDAA) from wheat in pullets have not yet been fully established, limiting precision formulation. This study aimed to evaluate the physical properties, conventional nutritional components, amino acid profiles and SIDAA in 10 wheat samples from different sources when fed to pullets during brooding (d 28-31) and growing (d 92-95) periods, and to develop SIDAA prediction equations base on physical properties, chemical components of wheats. A total of 594 and 396 Jingfen No.8 pullets, during brooding and growing periods respectively, were randomly assigned to one of 11 dietary groups. The diets included a nitrogen-free diet for measuring the basal endogenous losses of amino acids, and 10 test diets containing 92.53 % wheat as the sole source of amino acids. Moreover, all diets contained 0.5 % of titanium dioxide as indigestible indicator. The chemical components of the 10 wheat samples from different sources showed considerable variation. In particular, the coefficients of variation for ether extract (EE), crude fiber, neutral detergent fiber, calcium (Ca), and total phosphorus (TP) all exceeded 10 %. The SID values of the 15 analyzed amino acids differed significantly among 10 wheat samples (P < 0.05). During the brooding period, the SID of most amino acids were significantly correlated with gross energy (GE), crude ash, EE, Ca, methionine (Met), histidine (His), and tryptophane (Trp) (P < 0.05). During the growing period, the SID of most amino acids exhibited correlations with GE, crude ash, acid detergent fiber, TP, and essential amino acids, including Met, His and Trp (P < 0.05). Seventeen prediction equations were developed for each period: the serine equation showed the optimal model fit during brooding period (R² = 0.869), while four equations with R² > 0.80 were identified for the growing period. In conclusion, this experiment demonstrates that the chemical properties of wheat can be used to establish accurate equations for predicting the SID of most amino acids in pullets, serving as a reliable tool for rapid and accurate evaluation of amino acid nutritional value of wheat in pullets during both the brooding and growing periods.