The ban on antibiotics has stimulated renewed interest in non-antibiotic alternatives to manipulate rumen fermentation. Yeast cultures, mainly from strains of Saccharomyces cerevisiae (SC), have been the alternatives most studied and used in ruminants. Some consistent effects were observed at animal level (e.g. increase in DM intake and milk production), which seems to be related to the stimulation of cellulolytic bacteria (Newbold et al., 1996) and, thereby, increasing the potential to digest fibre in the rumen.
Such benefits in microbial population arise from the ability of SC to prevent a decline in rumen pH by decreasing lactate production and/or increasing utilization of lactic acid by some bacteria, oxygen scavenging and supply of growth factors (Jouany, 2006). Experimental support for the effects of SC on rumen fibre degradation, regardless of the digestibility of the basal diet, is inconsistent (Roa et al., 1997; Krehbiel et al., 2006).
The two experiments (Exp) described here were designed to examine the effects of a live yeast strain of SC (CNCM I-1077) on in situ ruminal degradation of 40 maize (MS; Exp. 1) and 66 grass silages (GS; Exp. 2). Within each type of silage, silages differed in chemical composition and in situ ruminal degradation. In both Exp, ruminal activity was also assessed through pH, volatile fatty acids (VFA), lactate and ammonia N (NH3-N) measurements.
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Article made possible through the contribution of Lallemand Animal Nutrition.