Influence of mouldy grass on fermentation and thiamine metabolism in bovine rumen fluid (in-vitro).

The influence of mouldy grass (kind of moulds: Fusarium sp., Epicoccum oryzae, Ulocladium spp., Mucor spp.) on the in-vitro-fermentation especially the thiamine-metabolism of bovine rumen fluid was investigated using the longterm rumen simulation technique (RUSITEC). Four investigation periods keeping 23 days each were carried out. After a control period of nine days (normal hay) an eight days lasting testphase followed. During this time two reaction vessels (KF) were charged with normal hay, two vessels (VF II) with mouldy grass and two (VF I) with a 50:50-mixture of normal hay and mouldy grass. During the last five days of the testperiod 0.3 mg thiamine/reaction vessel were added daily. In the last six days all reaction vessels were fed with normal hay. The following effects of mouldy grass during the investigation period on the rumen fluid and rumen gas, respectively, could be noted: changes of short volatile fatty acids concentrations (acetate -9.9% [p < 0.05] propionate up to -12.2% [ns], i-butyrate up to +39.9% [p < 0.001], n-butyrate up to +25% [p < 0.011]) increase of ammonia concentrations up to 68% (p < 0.01) small increase of pH for 0.08 units (p < 0.01) decrease of the methane production up to 16.6% (p < 0.001) increase of thiamine input due to the mouldy grass up to 310% (p < 0.05) increased breakdown of substituted thiamine for 44%.