No abstract

In vitro fermentations containing a mixed culture of ruminal bacteria (ruminal fluid from a hay-fed steer), buffer, and primarily rapidly degradable substrates (starch, glucose, cellulose, cellobiose, and trypticase) were inoculated with an overnight culture of Megasphaera elsdenii B159. Triplicate flasks were either uninoculated or inoculated to obtain a final concentration of 8.7 x 10(5) and 8.7 x 10(6) colony forming units of M. elsdenii per milliliter of culture fluid. Inoculation with M. elsdenii prevented an accumulation of lactic acid and excessive drop in pH. Lactate peaked at more than 40 mM in untreated cultures. In cultures inoculated with a low dose of M. elsdenii, lactate concentration peaked at approximately 25 mM at 5 h of fermentation but decreased rapidly to less than 5 mM by 7 h of fermentation. With the addition of the high dose of M. elsdenii, lactate was never greater than 2 mM (P < .05) throughout fermentation. Cultures treated with M. elsdenii had greater amounts (P < .05) of isobutyrate, butyrate, isovalerate, and valerate than untreated cultures. After 24 h of fermentation, one-half of the culture fluid was transferred to an equal volume of fresh buffer with substrate but was not inoculated with further quantities of M. elsdenii. Six hours after transfer, cultures that had been originally treated with M. elsdenii had lower (P < .05) amounts of lactate than untreated cultures. Inoculation with M. elsdenii has potential to prevent lactate accumulation in diets containing readily fermentable carbohydrates.

Live yeast culture (Saccharomyces cerevisiae) grew best on malt extract agar and required incubation under aerobic conditions to maximize the number of viable cells. In sterile, anaerobic ruminal fluid that had been supplemented with malt extract, yeast cells remained viable and metabolically active for up to 48 h, as indicated by the production of ethanol. A supplement containing live yeast and enzymes was fed twice daily with a diet of 50:50 (wt/wt) forage to concentrate (dry matter basis) to continuous fermentors inoculated with mixed ruminal microorganisms. The supplement had no effect on major fermentation acids or pH. After the last supplement with yeast was fed, numbers of yeast immediately decreased in the fermentors and were not detectable after 24 h. In the first of two lactation experiments, Holstein cows in midlactation were offered a diet with corn silage as the primary forage source. Half of the cows received a top-dressing based on corn that contained 10 g/d of the yeast and enzyme supplement. The supplement had no effect on milk production, milk composition, or dry matter intake. In a second lactation experiment, high producing cows in early lactation were fed 0, 10, and 20 g/d of the supplement. Cows fed the control diet produced 36.4 kg of milk/d, and milk production was 39.3 and 38.0 kg/d from cows fed 10 and 20 g of yeast/d, respectively.

N-Acetylglutamate (NAG) and N-acetylaspartate (NAA) are amino acid derivatives with reported activities in a number of biological processes. However, there is no published information on the presence of either substance in foodstuffs. We developed a method for extracting and quantifying NAG and NAA from soybean seeds and maize grain using ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). The lower limit of quantification for both NAG and NAA was 1 ng/mL. The method was then utilized to quantify NAG and NAA in other foodstuffs (fruits, vegetables, meats, grains, milk, coffee, tea, cocoa, and others). Both NAG and NAA were present in all of the materials analyzed. The highest concentration of NAG was found in cocoa powder. The highest concentration of NAA was found in roasted coffee beans. Both NAG and NAA were found at quantifiable concentrations in all foods tested indicating that these two acetylated amino acids are common components of the human diet.