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-[2-13C]lactate fermented via the acrylate pathway and the percentage of DL-lactate fermented to butyrate can be measured with 13C-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.High-concentrate diets induce a rapid microbial fermentation in the rumen and the accumulation of intracellular (H) within the microbes leads to an increased formation of reduced end products and of lactic acid (4). This in itself should not lead to DL-lactate accumulation in the rumen, provided that the capacity to remove DL-lactate was high enough. DL-Lactate formed in the rumen may be removed in three ways: (i) by passage to the lower gastrointestinal tract, (ii) by absorption directly from the rumen, and (iii) by microbial fermentation.Megasphaera elsdenii, a predominant DL-lactate-fermenting organism, shows no catabolite repression by carbohydrates such as glucose and maltose, whereas Selenomonas ruminantium subsp. lactilytica, another predominant DL-lactate-fermenting organism, ferments glucose, sucrose, and xylose first before fermenting DL-lactate (7, 11).M. elsdenii is commonly considered to be associated with the fermentation of readily fermentable carbohydrates (9,14). Therefore, it is important to know the participation of M. elsdenii in the fermentation of DL-lactate under several feeding conditions, in different animals, and especially after feeding readily fermentable

No abstract

No abstract

Abstract. An empirical method for the calculation of the carbon chemical shifts of allene carbons is developed. The method is successful in predicting the chemical shifts in a wide variety of substituted allenes. The effect of the electronegativity of substituents, with respect to the chemical shift contributions, is discussed. Experimental chemical shift increment values show a linear correlation with both the calculated diamagnetic shielding effects and the Pauling electronegativities for first row elements of the periodic system directly ,attached to the allene For many years the synthesis and chemical properties of allenes have been a major area of interest in this laboratory*. In our NMR research group we have studied the 'H and

No abstract