[Effects of orally administered substances on rumen fermentation patterns in cattle (in vitro). 7. Effect of dried yeast in chronic ruminal acidosis].

The influence of dried yeast on the in-vitro-fermentation of chronic acidotic bovine rumen fluid was investigated using the longterm rumen simulation technique (RUSITEC). Five investigation periods keeping 21 days each were carried out. After a control period of eight days a five days lasting test phase followed. During this time 2 g of dried yeast were added to two reaction vessels and two reaction vessels remained as controls. The following effects of dried yeast during the investigation period on rumen fluid and rumen gas, respectively, could be noted: negligible increase of pH for 0.1 units (ns) increase of short volatile fatty acids concentrations up to 10% (p < 0.01), (acetate +1.5% [ns], propionate +6.0% [ns], i-butyrate up to +180% [p < 0.001], n-butyrate 0%, i-valerinate +39%, [p < 0.05], n-valerinate +17.6% [p < 0.001], hexanat +33% [p < 0.001]) increase of gas production up to 29% (p < 0.001) decrease of methane production up to 30% (ns) increase of hydrogen production up to 10% (ns) increase of protein concentrations up to 23% (p < 0.05) increase of ammonia concentrations up to 385% (p < 0.001). The fermentation patterns became normal during 6 days after withdrawal of the yeast.