Effects of feed intake level on the additivity of apparent and standardized ileal digestibility of amino acids in diets for growing pigs

Abstract The present study was conducted to evaluate the additivity of apparent (AID) and standardized (SID) ileal digestibility of AA in diets at two feed intake (FI) levels. A total of 28 growing barrows were used in this study with 7 treatments and two 10-d experimental periods (7 d adaptation and 3 d ileal digesta collection). The seven treatments contained 3 experimental diets (Corn, SBM, and Corn + SBM mixed diet) at 2 feeding levels (low and high, represented 3% of BW per day and ad libitum, respectively) in a 3 × 2 factorial arrangement and a nitrogen-free diet (NFD) fed at low feeding level. There were 8 replicates for each of the 7 treatments. The AID of AA determined in low FI was greater than the AID determined in high FI levels for nitrogen and all AA except for Leu, Met, Cys, and Tyr in corn, SBM, and the mixed diet (P