[en] Increasing attention has been paid to dietary fibre (DF) fermentation in the large
intestine of pigs during the past years in pig nutrition. The bacterial growth supported
by DF intestinal fermentation induces a shift of N excretion from urea in urine to
bacterial protein in faeces that reduces NH3 emission from the manure. The objective of
this thesis was to investigate the relationship between DF fermentability, intestinal
bacteria growth and the N excretion.
In the first part, an in vitro gas-test method using a living bacterial inoculum developed
for ruminants was adapted to the pig. The use of pig colonic content was compared to
faeces for the preparation of the inoculum and it was concluded that faeces could
replace intestinal content, avoiding the use of cannulated animals. Secondly, the
influence of a pespin-pancreatin hydrolysis prior to the fermentation in order to
simulate digestion in the stomach and the small intestine was demonstrated. Finally, the
influence of the faeces donnor bodyweight and the dietary fibre content of its diet on
the gas production kinetics was shown. When studying a topic related to a specific
category of pig, it is recommended to use animals from the same category as faeces
donors to prepare the inoculum.
In the second part of the thesis, the amount of protein synthesis (PS) by faecal microbes
fermenting different sources of purified carbohydrates, or ingredients differing in DF
content, was measured using 15N-labelled NH4Cl in the inoculum. PS ranged between
9.8 and 22.9 mg N g-1 fermented carbohydrate according to the rate of fermentation of
the carbohydrate and its soluble fibre content. These in vitro observations were
confirmed through in vivo experiments with diets containing increasing levels of
soluble DF: in vitro PS passed from 1.51 to 2.35 mg N g-1 diet while in vivo urinary-
N:fecal–N excretion ratio decreased from 2.171 to 1.177.
