Hydrolysis and fermentation rate of glucose, sucrose and lactose in the rumen

The objective of this experiment was to estimate the rate of hydrolysis and fermentation of sugars in the rumen of cows either adapted or unadapted to sugar in the diet. The experimental design was a 3 x 3 Latin square with three rumen- and duodenal-fistulated dairy cows, given a basal diet with addition of zero (0), 0.6 kg sucrose (S) or 0.6 kg lactose (L). The concentration of individual soluble sugars and polyethylene glycol (PEG) in the rumen of cows was measured after introduction of a single dose of the sucrose, lactose or glucose through the rumen cannula. The rate of hydrolysis of sucrose varied from 1200 to 1404% h(-1) and was not affected by addition of sugars to the basal diet. The rate of hydrolysis of lactose was 248 and 204% h(-1) for treatment 0 and S, but was considerable higher (540% h(-1)) when lactose was added to the basal diet. The rate of glucose fermentation after glucose dosing varied from 422 to 738% h(-1), and increased with both sucrose and lactose addition to the diet. The rate of fermentation of monosaccharides originating from disaccharide hydrolysis was very high, from approximately 300 to 700% h(-1).