Microbial thiamin metabolism in the rumen simulating fermenter (RUSITEC): the effect of acidogenic conditions, a high sulfur level and added thiamin

Abstract

The effects of acidogenic conditions, a high S level and the addition of thiamin on the rumen microbial metabolism of thiamin were investigated in vitro in a semi-continuous fermenter (RUSITEC), using a factorial design. Acidogenic conditions were obtained by simultaneously increasing the starch : cellulose ratio and the amount of solid substrate fed, and by decreasing the buffering capacity of the liquid phase of the fermenter. S in the form of sulfate was supplied at two levels, one corresponding to a control amount of S (2 g/kg dietary DM), the second to an excess (5 g/ kg DM) which is sufficient to trigger cerebrocortical necrosis (CCN) when used in vivo. Acidogenic conditions decreased the pH of the fermenters, CH4 production and cellulose digestibility, increased the short-chain fatty acid production, but had no effect on thiamin production. The high S level enhanced the production of sulfide considerably, had no effect on the microbial metabolism of energy and N, and decreased thiamin production (326 Y. 266nmoYd). The added thiamin was rapidly converted into phosphorylated compounds which largely decreased the apparent synthesis of this vitamin by the rumen microflora. The total thiamin flow was increased by added thiamin. In no case was thiaminase activity in the fermenter liquid phase significantly modified. The high level of S induced only a limited decrease of total thiamin flow. Consequently, it is unlikely that the investigated factors could be considered to be high risk factors for the thiamin-dependent CCN.

Effect of dietary supplementation with treated amaranth seeds on fermentation parameters in an artificial rumen

“…The stoichiometric parameters of rumen fermentation (organic matter fermented (OMF) (Van Nevel and Demeyer, 1977), amount of microbial nitrogen (N M ), efficiency of microbial synthesis (EMS)) were calculated according to Alves de Oliveira et al (1997). …”

Effect of microbial oil, monensin and fumarate on rumen fermentation in artificial rumen

“…Dry matter, ash and nitrogen were determined according to the methods of the Association of Official Analytical Chemists (AOAC, 1980). Nitrogen (N) incorporated by the microflora (N M ) was estimated as the difference between total nitrogen N T (nitrogen in the effluent + bag feed residue) and NH 3 -N (N M = N T -NH 3 -N) in mg/g (Alves de Oliveira et al, 1997). The other fermentation variables -fermentation efficiency (Orskov et al, 1968), organic matter fermented OMF (Demeyer and Van Nevel, 1979), production, utilization and recovery of metabolic hydrogen (Demeyer, 1991) were calculated according to the stoichiometry of rumen fermentation.…”

Effects of different dietary concentrate to forage ratio and thiamine supplementation on the rumen fermentation and ruminal bacterial community in dairy cows

“…However, none of these approaches has consistently maintained higher and stable ruminal pH. De Oliveira et al (1997) and Tafaj et al (2006) observed that the adequate status of thiamine in ruminants can be altered by SARA conditions and this can lead to cerebrocortical necrosis, which is particularly associated with intensive feeding systems and high-concentrate diets in dairy cattle. Our previous research found some evidence that adding 180 mg thiamine/kg could alleviate SARA by increasing the rumen pH and decreasing the lactate concentration by regulating the structure of rumen microbial community in vitro (Pan et al 2013).…”