The effect of high and low dietary crude protein and i finisher pigsn lin supplementation on nutrient digestibility, nitrogen excretion, intestinal microflora and manure ammonia emissions from

A 232 factorial experiment was performed to investigate the interaction between a high- and low-crude-protein (CP) diet (200 v. 140 g/kg) and inulin supplementation (0 v. 12.5 g/kg) on nutrient digestibility, nitrogen (N) excretion, intestinal microflora, volatile fatty acid (VFA) concentration and manure ammonia emissions from 24 boars (n56, 74.0 kg live weight). The diets were formulated to contain similar concentrations of digestible energy and lysine. Pigs offered the high-CP diets had a higher excretion of urinary N (P,0.001), faecal N (P,0.01) and total N (P,0.001) than the pigs offered the low-CP diets. Inulin supplementation increased faecal N excretion (P,0.05) and decreased the urine N : faeces N ratio (P,0.05) compared with the inulin-free diets. There was no effect (P.0.05) of dietary treatment on N retention. There was an interaction (P,0.05) between dietary CP concentration and inulin supplementation on caecal Enterobacteria spp. Pigs offered the diet containing 200 g/kg of CP plus inulin decreased the population of Enterobacteria spp. compared to those with the inulinsupplemented 140 g/kg CP diet. However, CP level had no significant effect on the population of Enterobacteria spp. in the unsupplemented diets. Inulin supplementation increased caecal Bifidobacteria (P,0.01) compared with the inulin-free diets. There was no effect of inulin supplementation on VFA concentration or intestinal pH (P.0.05). Pigs offered the 200 g/kg CP diets had higher (P,0.05) manure ammonia emissions from 0 to 240 h of storage than pigs offered the 140 g/kg CP. In conclusion, inulin supplementation resulted in an increase in Bifidobacteria concentration and a reduction in Enterobacteria spp. at the high CP level indicating that inulin has the ability to beneficially manipulate gut microflora in a proteolytic environment.