In Vitro Fermentation of Sugars, Grains, and By-Product Feeds in Relation to Initiation of Ruminal Lactate Production

In vitro fermentations of various sugars, grains, and by-products were conducted to investigate the relationships between soluble carbohydrates and initiation of ruminal lactate production. Fermentation of hexose sugars, both monosaccharides and disaccharides, resulted in greater accumulation of lactate than did fermentation of pentoses. Results of fermentation of grains and by-products, in order of greatest to least potential to produce lactic acid, were steam-flaked barley = barley = wheat > citrus pulp > beet pulp = corn > high moisture corn = sorghum grain. Water-soluble fractions of the grains and by-products were more rapidly fermented to lactate than the insoluble fractions. Combining 10% soluble fractions from wheat, barley, and steam-flaked barley with 90% insoluble fractions from corn resulted in significant increases in lactate concentration. Analysis of sugar composition of these water soluble materials indicated that monosaccharides and disaccharides constitute 23 to 46% by weight. Data suggest that water-soluble materials play a role in initiation of lactate production from grains, and further production is dependent on starch fermentability.