The end-products of dietary carbohydrate fermen-tation catalysed by rumen microflora can serve as the primarysource of energy for ruminants. However, ruminants providedwith continuous carbohydrate-containing feed can develop ametabolic disorder called“acidosis”. We have evaluated thefermentation pattern of both soluble monomeric and non-soluble polymeric carbohydrates in the rumen in in vitro fer-mentation trials. We found that acidosis could occur within 6 hof incubation in the rumen culture fermenting sugars andstarch. The formation of lactic acid and acetic acid, eitheralone or in mixture with ethanol, accounted for high build-up of acid in the rumen. Acidosis resulted even when only20% of a normal daily feed load for all soluble and non-soluble carbohydrates was provided. DNA-based microbialanalysis revealed thatPrevotellawas the dominant microbialspecies present in the rumen fluid

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• In vitro rumen fermentation of soluble and non-soluble polymericcarbohydrates in relation to ruminal acidosis