Propionate Production in the Rumen of Cows Fed Either a Control or High-Grain, Low-Fiber Diet

Rumen propionate production is cows fed either a control diet or a high-grain, low-fiber diet was measured by isotope dilution technique. The high-grain, low-fiber diet resulted in the characteristic decrease in milk fat per cent (50% reduction) and a decreased molar ratio of acetate:propionate. Propionate production on the two diets was 13.3 and 31.0 moles/day for the control and high-grain, low-fiber diets. These results coupled with our previous studies (3) indicate the change in the molar ratio of rumen volatile fatty acids for cows fed a high-grain, low-fiber diet is the result of an increase in propionate production rather than a decrease in acetate production.