Effect of glucose on fermentation heat in sheep rumen fluid in vitro

Abstract

1. Heat production rate (H) of rumen fluid was measured in a direct calorimeter, Basal H of samples of 15 ml rumen fluid mixed with 45 ml buffer was 0.4 mW/ml rumen fluid.2. Addition of glucose (0.4–6.4 mg/sample) was followed by a dose-dependent increase in H. Maximal H was 1.1 rnW/ml and lasted up to 5 min, returning thereafter to the basal level.3. Expression of fermentation heat (Hf; kJ/mol substrate added) against glucose dose indicated an asymptotic dose response.4. Maximal Hf(at infinite dilution) agreed with stoichiometric calculations whereas minimal Hfsuggested a partial fermentation of the substrate at a high-glucose dose in the rumen environment.