Basal ileal endogenous losses of amino acids in pigs determined by feeding nitrogen-free diet or low-casein diet or by regression analysis

Abstract

The aim of this study was to compare the basal ileal endogenous losses (BEL) of amino acids (AA) in pigs determined by feeding nitrogen-free diet (NFD) or low-casein diet (LCD) or by regression analysis. Barrows with an initial body weight (BW) of 50.5 ± 4.46 kg were surgically fitted with T-cannulas at the distal ileum prior to the experiment. A triplicate 6 × 3 incomplete Latin square design was applied with 3 blocks of BW, 6 pigs per block, 6 dietary treatments, and 3 experimental periods. Four of the 6 dietary treatments were used in the current study. The NFD was prepared based on cornstarch and dextrose, and casein was added at 0, 60, 100, or 140 g/kg to NFD at the expense of cornstarch. The diet containing 60 g/kg casein was considered as LCD in further analysis. In each experimental period, pigs were adapted to the experimental diets for 5 days followed by 2 days of ileal digesta collection. The BEL of AA in pigs fed NFD and LCD were estimated based on the assumption that the contents of AA in ileal digesta samples completely originated from pigs. The concentration of ileal apparent digestible AA in diets containing casein was determined and regressed against the concentration of AA in diets to estimate the BEL of AA as y-intercept. The BEL of isoleucine, glutamate, and serine in pigs fed LCD were greater (P < 0.05) than those in pigs fed NFD but were not different from the values estimated by regression analysis. There was no difference in the BEL of the other AA among the 3 methods. In conclusion, the BEL of AA, except isoleucine, glutamate, and serine, could be estimated by feeding NFD or LCD or by regression analysis.