The use of live microorganisms as feed supplements for ruminants is not a new concept.
The use of microbial preparations has been largely based on empirical observations that suggest that some types of live microorganisms in feeds may beneficially influence animal performance in many types of production systems.
Relatively speaking, large-scale applications of live microorganisms in feeds were not common historically.
However, in the two last decades, the potential roles of specific microbial supplements have been better defined and there has been considerable interest in using preparations containing live microorganisms as feed supplements for ruminants (Dawson, 2002).