Effect of fumaric acid supplementation and dietary buffering capacity on the concentration of microbial metabolites in ileal digesta of young pigs

Experiments were conducted to determine the effect of different levels of f umaric acid supplementation to diets with a low or high buffer capacity on the concentrations of microbial metabolites and lipopolysaccharides, as an indicator of gram negative bacteria in ileal digesta of young pigs. In two experiments, 12 pigs each were weaned at 14 d of age and fitted with a simp le T-cannula at the distal ileum between 15 and 17 d of age. In experiment 1, the pigs were fed wheat-soybean meal diets without or with inclusion of 1, 2 or 3% fumaric acid according to a balanced two-period changeover desig n. In experiment 2, the same diets were fed, except that the dietary buffer ing capacity was increased by inclusion of 3% sodium bicarbonate to all die ts. The pigs were fed three times daily, equal amounts at 8 h intervals. Th e diets were supplied at a rate of 5% (wt/wt) of body weight. The inclusion of fumaric acid to the diet with a low buffering capacity (exp. 1) decreas ed (P < 0.05) the concentrations of lactic acid, ammonia, spermidine and li popolysaccharides in ileal digesta. Supplementation of fumaric acid to a di et with a high buffering capacity (exp. 2) did not affect (P > 0.05) the co ncentrations of fermentation products in ileal digesta, but there was a dec rease (P < 0.05) in the concentration of lipopolysaccharides. Furthermore, in both experiments, the concentration of most fermentation products decrea sed (P < 0.05) with increasing age after weaning. These results give furthe r evidence that supplementation of fumaric acid to diets for young pigs dur ing the first 3 - 4 wk after weaning reduces the metabolic activity and the concentrations of bacteria in the gastrointestinal tract. The magnitude of this effect, however, is dependent on the buffering capacity and the inclu sion level of fumaric acid in the diets.