Title of article :
Effects of a dietary organic acid mixture and of dietary fibre levels on ileal and faecal nutrient apparent digestibility, bacterial nitrogen flow, microbial metabolite concentrations and rate of passage in the digestive tract of pigs
Abstract :
Six 34-kg barrows were fitted with a post-valve T-caecum cannula and assigned to six dietary treatments according to a 6 £ 5
change-over design to study how a mixture of formic acid, sorbate, and benzoate (0 or 8.4 g/kg feed) influences apparent ileal
and faecal digestibility coefficients, bacterial nitrogen (N) flow, microbial metabolite concentrations, and passage rate in pigs fed
isoenergetic diets with medium, high, or very high fibre content (neutral-detergent fibre (NDF): 199, 224, and 248 g/kg dry matter,
respectively). These barley and soya-bean meal based diets contained 0, 75, and 150 g/kg barley fibre (NDF: 577 g/kg) and 0, 8,
and 16 g/kg rapeseed oil, respectively. The dietary organic acid mixture improved the apparent ileal digestibility of 14 of the 17
amino acids analysed (P , 0.05). Increasing levels of dietary fibre linearly decreased the apparent ileal digestibility of six of the
17 amino acids analysed (P , 0.05). Ileal flows of bacterial N and amino acids as assessed on the basis of purine flow were
decreased by the dietary organic acid mixture (P , 0.05) but were not affected by dietary fibre level (P . 0.05). As assessed on
the basis of diaminopimelic acid flow, bacterial N flow was increased by both the dietary organic acid mixture and increased
dietary fibre levels (P , 0.05). The dietary organic acid mixture reduced the concentration of lactic acid and increased that of
acetic acid in ileal digesta (P , 0.05), while dietary fibre levels had a quadratic effect on concentrations of acetic, propionic, and
butyric acid (P , 0.05). The mean retention time of Co (solute marker) and Yb (particle marker) in the large intestine decreased in
a linear manner by increasing dietary fibre levels (P , 0.05) but was not affected by the dietary organic acid mixture (P . 0.05).
The results show that a dietary organic acid mixture has a positive effect on the apparent ileal digestibility of most amino acids
irrespective of dietary fibre levels. This could be at least partly related to changes in bacterial N flow in the ileum. However,
different bacterial markers showed opposite effects on bacterial N flow, which makes it questionable to use a constant bacterial
marker / bacterial N ratio to estimate bacterial N flow. Increasing levels of dietary fibre had negative effects on the apparent ileal
amino acid digestibilities and shortened the mean retention time of digesta in the large intestine.
Keywords :
bacterial protein , Digestibility , retention time , pigs, , organic acids