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PubMed1995

Rumen fermentation and metabolic profile in conventional and gnotobiotic lambs.

Observations were carried out of actual acidity, volatile fatty acid (VFA) concentrations, enzyme activity in the rumen, total protein, urea, total lipid and glucose in the serum of conventional (CL) and gnotobiotic lambs (GL) in the period of milk nutrition. The inoculum of gnotobiotic lambs contained Streptococcus bovis, Prevoxella ruminicola, Butyrivibrio fibrisolvens and Selenomonas ruminantium at a concentration of 1.10(6) each. Throughout the observation period the pH of the rumen contents of gnotobiotic lambs ranged within 6.5-6.8 with a significant difference at an age of 7 weeks. Total VFA concentrations in the rumen contents were increased in the CL throughout milk nutrition: the differences at 4 and 5 weeks of age were significant. Total VFA in the conventional lambs revealed an increasing tendency between weeks 4 and 7, reaching higher levels at 7 weeks of age (57.1 mmol.l-1), whereas in the gnotobiotic animals the range (24.3-30.1 mmol.l-1) was narrow and the peak occurred at 6 weeks of age. In GL significantly increased molar proportions of acetic acid were observed whereas in CL the molar proportions of propionic acid proved to be significant increased. The molar proportions of butyric and valeric acids were increased in CL but the group differences were not significant. In GL no isoacids were found. Alpha amylase (E.C.3.2.1.1.) activity of the rumen contents was significantly increased in GL between weeks 2 and 6 of age whereas cellulase (endoglucanase E.C.3.2.1.4. and cellobiohydrolase E.C.3.2.1.91.) activity was significantly increased in 4-week-old CL. Over the whole period of milk nutrition no significant differences were observed in urease (E.C.3.5.1.5.) activity of the rumen contents in the examined groups. At 5 weeks of age significantly increased total protein levels were observed in the conventional animals with maximum levels occurring at 4 weeks of age (CL-59.5 g.l-1 GL-55.3 g.l-1). Urea levels in 6-week old conventional lambs were significantly higher than in the gnotobiotic animals (CL-6.4 mmol.l-1 vs. GL-1.9 mmol.l-1). As to glycaemia no significant group differences were recorded. In the conventional animals total lipid levels were significantly increased at 1 and 6 weeks of age with a peak occurring in the first week of life (7.5 g.l-1) whereas in the gnotobiotic lambs a significant increase was observed at 3 weeks of age, the peak being recorded in 4 week-old animals (4.3 g.l-1). Throughout the period of interest the mean daily weight gains in the conventional and gnotobiotic lambs presented 0.164 and 0.162 kg, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1981

Volatile Fatty acids and hydrogen as substrates for sulfate-reducing bacteria in anaerobic marine sediment.

The addition of 20 mM MoO(4) (molybdate) to a reduced marine sediment completely inhibited the SO(4) reduction activity by about 50 nmol g h (wet sediment). Acetate accumulated at a constant rate of about 25 nmol g h immediately after MoO(4) addition and gave a measure of the preceding utilization rate of acetate by the SO(4)-reducing bacteria. Similarly, propionate and butyrate (including isobutyrate) accumulated at constant rates of 3 to 7 and 2 to 4 nmol g h, respectively. The rate of H(2) accumulation was variable, and a range of 0 to 16 nmol g h was recorded. An immediate increase of the methanogenic activity by 2 to 3 nmol g h was apparently due to a release of the competition for H(2) by the absence of SO(4) reduction. If propionate and butyrate were completely oxidized by the SO(4)-reducing bacteria, the stoichiometry of the reactions would indicate that H(2), acetate, propionate, and butyrate account for 5 to 10, 40 to 50, 10 to 20, and 10 to 20%, respectively, of the electron donors for the SO(4)-reducing bacteria. If the oxidations were incomplete, however, the contributions by propionate and butyrate would only be 5 to 10% each, and the acetate could account for as much as two-thirds of the SO(4) reduction. The presence of MoO(4) seemed not to affect the fermentative and methanogenic activities; an MoO(4) inhibition technique seems promising in the search for the natural substrates of SO(4) reduction in sediments.

Journal Article↗
PubMed1966

Conversion of C-labeled substrates to volatile Fatty acids by the rumen microbiota.

The fermentation of uniformly labeled glucose-C, glucose-1-C, -2-C, and -6-C, xylose-1-C, cellulose-1-C, -2-C, and -6-C, and lactate-2-C by rumen fluids from cows fed all-hay, hay and concentrate (50:50), and all-concentrate diets was investigated. The results obtained suggested that the Embden-Meyerhof glycolytic pathway is the major pathway of hexose utilization, that the major pathway of xylose fermentation involves hexose synthesis, and that the contributions of the nonrandomizing (acrylate) pathway of propionate formation during glucose, xylose, and cellulose fermentations are 4.5, 8.0, and 10.5%, and 24.6, 25.8, and 17.2%, respectively, by rumen fluids from the cows fed all-hay and all-concentrate rations.

Journal Article↗