Effects of age and rapeseed meal source on the ileal amino acid digestibility of broilers

Context Accurate prediction of amino acid (AA) digestibility in rapeseed meal (RSM) for broilers is critical for improving feed utilization and reducing nitrogen emissions. Aims To determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA of rapeseed meal (RSM) in 13- and 28-day-old broilers. Ten RSM-samples were obtained from different processing plants in China. Methods In total, 858 1-day-old Arbor Acres male broilers were used in the study. There were 11 treatment groups, including 10 RSM diet groups and 1 N-free diet group, to allow determination of endogenous AA loss. The diets were fed in two stages from Day 10 to Day 13 and from Day 25 to Day 28. Each diet was supplemented with 0.5% titanium dioxide as an indigestible marker. On Day 10, 528 broilers were randomly allotted to treatments with six replicate cages of eight birds per cage for each treatment. On Day 25, 330 broilers were randomly allotted to treatments with six replicate cages of five birds per cage for each treatment. Key results In 10 RSM samples, the mean values of crude protein (CP), total AA, indispensable AA and dispensable AA were 43.45% (CV 5.54%), 37.57% (CV 6.28%), 17.28% (CV 6.82%) and 20.29% (CV 6.27%) respectively. The interaction between the RSM source and broiler age significantly (P < 0.05) affected the AID and SID of all AA except for Asp and Pro. There were significant (P < 0.05) differences in the SID and AID of all AA among RSM samples. As the age of broilers increased, the AID and SID of most AA increased (P < 0.05). Conclusions The results from this study indicate that the AID and SID of AA differed among RSM sources. The AID and SID of most AA increased with increasing age independent of RSM source. Implications The data in this study are a reference for the efficient utilization of RSM in broiler diets.