Establishment of cellulolytic bacteria and development of fermentative activities in the rumen of gnotobiotically-reared lambs receiving the microbial additive Saccharomyces cerevisiae CNCM I-1077

We studied the effects of a yeast additive used in ruminant nutrition on th e establishment of cellulolytic bacteria, on plant cell wall degradation an d on digestive functions in the rumen of gnotobiotically-reared lambs. Cell ulolytic bacteria inoculated to the lambs tended to become established earl ier in the presence of Saccharomyces cerevisiae CNCM I-1077 (SC). In additi on, their population was maintained at a higher level, when the physico-che mical conditions of the biotope were altered. In these lambs, specific acti vities of fibrolytic enzymes were greater, and in sacco degradation of whea t straw tended to increase. In the presence of SC there was a decrease in r uminal ammonia concentration and a higher volatile fatty acid (VFA) concent ration when lambs were 20 to 50 days old. These data suggest that this yeas t strain may stimulate the development of cellulolytic microflora and enhan ce microbial activity in the rumen of young ruminants. Such activity could be beneficial in preventing microbial imbalance and a reduction of rumen fu nction efficiency in the case of nutritional transitions. Further studies w ith conventional animals will soon be performed in order to verify these fi ndings.