In vitro fermentation of grain and enzymatic digestion of cereal starch

Fermentation of grain in the rumen and the digestion of starch in the small intestine are influenced by both animal and grain characteristics. Two assays were established to determine the importance of grain characteristics on fermentation and enzyme digestion. To simulate microbial fermentation in the rumen finely milled samples of grain were incubated in rumen fluid and the end products of fermentation and starch disappearance were measured. The second assay was based on amylase and amyloglucosidase and was established to simulate starch digestion in the small intestine. The assays identified large differences between and within grains with respect to both susceptibility of grain to microbial fermentation and enzyme digestibility of starch. Ranking grains on the basis of total acid production identified expected differences between grains. Lactic acid was positively correlated to total acid production, which implies that strategies aimed at increasing the rate of fermentation of grain inevitably increase the risk of rumen acidosis. The assays identified a sorghum cultivar with a higher rate of fermentation and enzyme digestibility compared to other sorghum varieties tested. Triticale was also identified as a grain with a high enzyme digestibility of starch.