Apparent digestibility (ileal and overall) of nutrients and endogenous nitrogen losses in growing pigs fed wheat (var. Soissons) or its by-products without or with xylanase supplementation

Abstract

The main aims of this experiment were: 1) to study the sites and extent of digestion of the nutrients in wheat (var. Soissons) and its by-products (bran, middlings) and in recombined wheat (flour+bran+middlings); 2) the contribution of microbial action (VFA apparent production) and endogenous secretion of N in the small intestine; and 3) interactions with an exogenous non-starch polysaccharide (NSP) degrading enzyme (xylanase). The post valve “T” caecal cannulae (PVTC, 12 pigs) and end-to-end ileo-rectal anastomosis (IRA, 30 pigs) ileal digesta collection methods with TiO 2 and Cr 2O 3 as the indigestible markers, and the 15N-isotope dilution technique were used in this study. Four diets, based on wheat (W), recombined wheat (WR), wheat plus bran (WB) or wheat plus middlings (WM) were used without or with xylanase addition. NSP content was highest in the diet based on wheat bran and lowest in the W and WR diets. Recombination of the milled fractions had no effect on digestibility values relative to the ground wheat. Negative correlations ( P<0.001) occurred for apparent overall and ileal digestibility of dry matter (DM), energy, crude protein (CP) and amino acids with NSP content. As shown in some previous studies, NSP contributed to a higher ileal flow of endogenous nitrogen ( P<0.001) and volatile fatty acids (VFA) ( P=0.021) and the proportion of DM fermented in the large intestine was increased ( P<0.001). Although statistically significant ( P<0.05), the improvements associated with enzyme addition in overall apparent digestibility of DM, CP and gross energy were only of the order of 1% and those at the ileal level were less than 2% ( P>0.05). However, with the WB diet the improvements for all three parameters were approximately 2% for overall apparent digestibility and 4% for ileal apparent digestibility.