Apparent and standardized ileal amino acid digestibility of corn and wheat in 10- to 14-day-old Japanese quail using the nitrogen-free diet method.

Accurate age-specific information on amino acid digestibility is needed for precision formulation of diets for young Japanese quail. Following our previous evaluation of corn and wheat in older quail, this study determined the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids in corn and wheat during the 10-14-day post-hatch period, representing an earlier starter phase than that evaluated previously. A total of 300 quail chicks were assigned to three treatments in a completely randomized design with five replicates of 20 birds each. Treatments consisted of a nitrogen-free diet (NFD) to estimate basal endogenous losses and corn- or wheat-based diets in which the test ingredient served as the sole source of protein and amino acids. Titanium dioxide (5 g/kg) was included as an indigestible marker. After a 5-d feeding period, ileal digesta were collected and amino acid concentrations in feed and digesta were determined by HPLC following acid hydrolysis. Basal endogenous amino acid losses ranged from 97.20 mg/kg dry matter intake (DMI) for aspartic acid to 802.78 mg/kg DMI for proline, with substantial variation among amino acids. In corn, AID and SID values ranged from 70.21 to 94.30% and from 83.96 to 97.53%, respectively, whereas corresponding values for wheat ranged from 77.96 to 90.81% and from 84.15 to 95.48%. The magnitude and direction of differences between ingredients varied among amino acids. Corn exhibited higher SID values for lysine, valine, threonine, and arginine, whereas wheat showed higher SID values for glutamic acid, glycine, leucine, histidine, alanine, and serine (P < 0.05). Although the magnitude of differences varied among amino acids, methionine exhibited relatively small differences between ingredients, whereas aspartic acid showed only moderate variation. These findings demonstrate substantial ingredient-specific variation in amino acid digestibility and emphasize the importance of using species-specific digestibility coefficients when formulating diets for growing Japanese quail.