Role of Megasphaera elsdenii in the Fermentation of dl -[2- 13 C]lactate in the Rumen of Dairy Cattle

Abstract

Since Megasphaera elsdenii ferments a variable part of dl -lactate to butyrate, measurement of the percentage of dl -lactate fermented to propionate via the acrylate pathway in rumen contents will underestimate the participation of M. elsdenii in the dl -lactate fermentation. The percentage of dl -[2- 13 C]lactate fermented via the acrylate pathway and the percentage of dl -lactate fermented to butyrate can be measured with 13 C-FT (Fourier transform)-nuclear magnetic resonance. On the average, the contribution of M. elsdenii to dl -lactate fermentation in the rumen of dairy cattle was found to be 74% (standard deviation, 13%), but differed with animal or diet. After feeding a cow readily fermentable carbohydrates, the contribution of M. elsdenii to the fermentation of dl -lactate increased as a consequence of catabolite repression in other dl -lactate-fermenting bacteria.