EFFECTS OF ORALLY-ADMINISTERED SUBSTANCES ON RUMINAL FERMENTATION PATTERNS IN CATTLE (IN-VITRO) .7. COMMUNICATION - INFLUENCE OF DRIED YEAST DURING CHRONIC RUMINAL ACIDOSIS

The influence of dried yeast on the in-vitro-fermentation of chronic a cidotic bovine rumen fluid was investigated using the longterm rumen s imulation technique (RUSITEC). Five investigation periods keeping 21 d ays 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 investiga tion period on rumen fluid and rumen gas, respectively, could be noted :negligible increase of pH for 0.1 units (ns) increase of short volati le fatty acids concentrations up to 10 % (p < 0.01), (acetate + 1.5 % [ns], propionate + 5.0 % [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 t o 29 % (p < 0.001) decrease of methane production up to 30 % (ns) incr ease of hydrogen production up to 10 % (ns) increase of protein concen trations up to 23 % (p < 0.05) increase of ammonia concentrations up t o 385 % (p < 0.001). The fermentation patterns became normal during 6 days after withdrawal of the yeast.