No abstract

In previous studies, dietary nucleotides have been shown to improve performance in single-stomached animals by promoting the renewal of small intestine epithelial cells and by influencing the activity and composition of the microbial community in the digestive tract. The present experiment was carried out with 12 barrows weaned at the age of 18 days and fitted with a simple T-cannula at the distal ileum. To determine short-term effects of dietary yeast nucleotides, the piglets received a grain-soybean meal-based basal diet with or without supplementation of 1 g/kg of a dried yeast product containing free nucleotides. Dietary supplementation with yeast did not affect bacterial numbers in the ileum as well as ileal concentrations of individual short-chain fatty acids (SCFA), total SCFA and total lactic acid (p > 0.05). Moreover, there was no effect of supplemental yeast nucleotides on ileal α-amylase, leucine amino peptidase, maltase and lactase activities (p > 0.05), as well as on ileal dry matter, crude protein and crude fibre digestibilities (p > 0.05). In conclusion, short-term supplementation with dietary yeast nucleotides did not affect microbial metabolite concentrations, bacterial numbers and enzyme activities in the ileal digesta as well as ileal nutrient digestibilities of newly weaned pigs.

The bacteria of the intestine have to cope with varying osmotic conditions in their ecosystem. In this in vitro study, the modified Hohenheim gas test (HGT) was used to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum, when fermenting different carbohydrates (inulin, corn starch, potato starch, cellulose, pectin), under normal buffered and osmotic stress conditions (elevated medium salinity). After 24 h of fermentation, gas, ammonia and short-chain fatty acid (SCFA) production was measured, and the cell numbers of total eubacteria, Lactobacillus spp., Bifidobacterium spp. and enterobacteria were analysed, using real-time polymerase chain reaction. There was a significant reduction in gas production after 24 h when comparing osmotic stress conditions with normal buffered conditions, and there were also differences among carbohydrates under both conditions. The content of SCFA was significantly lower when comparing osmotic stress with normal buffered conditions. Under osmotic stress, inulin and corn starch increased (p < 0.05) cell numbers of total eubacteria, while Bifidobacterium spp. and enterobacteria were higher (p < 0.05) when corn starch and pectin were fermented, respectively, in comparison to the other carbohydrates. The in vitro system of the modified HGT appears to be suitable to scrutinise effects of carbohydrates on the metabolic activity and composition of the microbial community under osmotic stress conditions, as they might occur during situations of osmotic diarrhoea.

These results suggest that only supplementation of a native betaine source but not of pure betaine products affects microbial fermentation under osmotic stress. Furthermore, both the carbohydrate and protein source play an important role in modifying microbial activity under osmotic stress conditions. It can also be concluded that the modified Hohenheim gas test is suitable to scrutinise fermentation activity of different assay substrates under osmotic stress.

In this in vitro study, the modified Hohenheim gas test was used to determine fermentation activity and bacterial composition of pig's faecal microbial inoculum, when fermenting a standard pig diet with varying levels of crude protein (CP; 20, 24 and 28% CP), and supplemented with one of three fibre sources manufactured by micronization treatment. These were wheat envelopes (MWE), pea fibre (MPF) and lupine fibre (MLF). For comparison, inulin was used. As intestinal bacteria have to cope with varying osmotic conditions in their ecosystem, fermentation was performed under normal buffered and osmotic stress conditions. After 24 h of fermentation, total gas production and ammonia production were measured. In addition, the effect of MWE and inulin on short-chain fatty acid (SCFA) production and numbers of total eubacteria, Lactobacillus spp., Bifidobacterium spp., Enterobacteriaceae, Enterococcus spp., Clostridium cluster XIVa and Clostridium cluster IV, were determined using quantitative real-time PCR. Under normal buffered conditions, supplementation of MWE resulted in increased (p < 0.05) SCFA, acetic, propionic and valerianic acid production at CP levels of 20 and 28%. There was an increase (p < 0.05) in ammonia production for the micronized supplements, and for MWE an increased (p < 0.05) branched-chain proportion was observed, possibly due to higher availability of protein for fermentation which was released during the micronization process. Osmotic stress conditions reduced (p < 0.05) total gas as well as total SCFA, acetic and propionic acid production for all treatments, while cell counts were increased (p < 0.05) for Bifidobacterium spp., Enterococcus spp. and Lactobacillus spp. Under normal buffered conditions in combination with 24 and 28% CP levels, lactobacilli were increased for MWE, compared to inulin (p < 0.05). In conclusion, micronized supplements such as MWE may beneficially modulate pigs' intestinal microbiota by increasing SCFA production in addition to a selective proliferation of lactobacilli.