An investigation into the influence of age on the standardized amino acid digestibility of wheat and sorghum in broilers

Standardized ileal digestibility coeffi-cients (SIDC) of nitrogen (N) and amino acids (AA) in wheat and sorghum at 6 different ages (d 7, 14, 21, 28, 35, and 42) of broilers were determined. Two assay diets were formulated to contain 93.8% of each grain as the sole source of AA in the diet. Titanium dioxide (0.5%) was added as an indigestible marker. Each assay diet was fed to 6 replicate cages housing 14 (d 7), 12 (d 14), 10 (d 21), 8 (d 28), 8 (d 35), and 6 (d 42) birds per cage for 4 d prior to ileal digesta collec-tion. The apparent ileal digestibility coefficients (AIDC) were standardized by using the age-appropri-ate basal endogenous AA losses. In the case of wheat, AIDC of N and all AA increased (linear or quadratic, P 0.05 to 0.001) with advancing age. No age effect was noticed on the SIDC of N, average of indispensable (IAA) and dispensable AA (DAA), though the average of total AA (TAA) tended (lin -ear, P = 0.09) to increase as birds grew older. In sor-ghum, the AIDC of N, average of IAA and DAA were unaffected (P 0.05) by age. The SIDC of N, average SIDC of IAA, DAA and TAA were higher at d 7, reduced at d 14 and then plateaued. Among the IAA, the SIDC of Arg, His, Ile, Leu, Lys, Thr, Val, and the SIDC of all individual DAA (except Cys) decreased with age (linear or quadratic, P < 0.05 to 0.001) with higher values at d 7. The higher SIDC values deter-mined at d 7 were due to higher EAA losses during wk 1. The results showed that broiler age influences AA digestibility and this may need be considered in prac-tical feed formulations. The age effect is variable depending on the grain type and specific AA.

Automated summary

The study found that the digestibility of nitrogen and amino acids in wheat increases with the age of broilers, while the digestibility in sorghum is less affected by age. The results also suggest that the digestibility of amino acids varies with age, highlighting the need to consider this factor in feed formulations.