Large intestinal fermentation capacity of fattening pigs on organic farms as measured in vitro using contrasting substrates.

BACKGROUND: In accordance with the EU regulations, organic farms require pigs to be fed diets high in fibre, which may impact on the pigs' large intestinal fermentation capacity. The ability of pigs to ferment non-starch polysaccharides (NSP) depends on characteristics of the dietary NSP source and microbes present in the large intestine of pigs. Little information exists on the fibre fermentation capacity of organically raised pigs. The aim of this study was to determine the variation in fibre fermentation capacity of fattening pigs within and between organic farms using an in vitro batch culture method and three contrasting substrates: oligofructose, soy pectin and cellulose. RESULTS: Pigs from different organic farms showed varying fermentation capacities as assessed by gas production, kinetics and fermentation end-products formed (P < 0.01). Coefficients of variation between inocula within farms varied by up to 40% for gas production and kinetics, in particular for incubation with cellulose. No relationship between on-farm feeding practice and the pigs' fermentation capacity could be established. CONCLUSION: The fermentation capacity of pigs reared under organic conditions varies considerable between farms. Finishing pigs reared under organic farming conditions are fast fermenters of oligofructose and soy pectin. More than four donor animals should be used per inoculum to accurately assess in vitro fermentation capacity. Fermentation results could not be related to dietary management under on-farm conditions.

Repeated measurements of in vitro fermentation of fibre-rich substrates using large intestinal microbiota of sows.

BACKGROUND: Fibrous ingredients for pig diets can be characterized by in vitro fermentation. In vitro fermentation methods often use a one-time measurement of gas production during the incubation of test substrates with one faecal inoculum. The representativeness of this approach can be questioned as measuring time and number of animals from which inoculum originates may influence fermentation results. An in vitro fermentation trial was conducted incubating three fibrous substrates with three inocula in five replicates (different fermentation runs) to test the influence of run and origin of inocula. RESULTS: Total gas production and maximal rate of gas production differed (P < 0.05) between fermentation runs, but less than substrates (P < 0.01). The ranking order between substrates remained similar for each run. Fermentation of cellulose led to higher coefficients of variation between inocula compared to the fast fermentable substrates oligofructose and soy pectin. Differences ranged from 2% for total gas production up to 25% for maximal rate of gas production. CONCLUSION: One fermentation run can provide representative results for substrate ranking. Using multiple inocula mixed from four faecal samples each leads to high coefficients of variation for slow fermentable substrates like cellulose. Future studies should examine the optimal number of animals for inocula preparation to decrease variation.