Arieli, A., Faculty of Agriculture, Rehovot, Israel.
Aharoni, Y., Faculty of Agriculture, Rehovot, Israel.
Zamwel, S., Faculty of Agriculture, Rehovot, Israel.
Tagari, H., Faculty of Agriculture, Rehovot, Israel.

The effect of ration on heat of glucose fermentation in sheep rumen fluid was investigated. Heat production was measured in a semiadiabatic calorimeter. In trial 1, the effect of glucose (.4 to 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25 or 100% roughage diet. Heat of glucose fermentation decreased with increase in glucose dose in both diets. Maximal heat of glucose fermentation in both diets agreed with stoichiometric calculations. However, at 6.4 mg glucose, maximal heat was 18 kcal/mol in the 25% roughage diet and 14 kcal/mol in the 100% roughage diet. Purine N and maximal rate of heat production were not affected by diet type. In trial 2, the effect of glucose (1.6 and 6.4 mg) on fermentative heat production was determined in rumen fluid from sheep fed 25, 50, 75, and 100% roughage. In addition, fermentation pattern was measured in donors of the rumen fluid. Heat of glucose fermentation was positively correlated with organic matter digestibility and negatively correlated with rumen pH and acetate concentration. These observations indicate that in addition to the effect of roughage on the fermentation pattern, supplemental adaptation may occur, as indicated by the reduction in the heat of glucose fermentation.