Implications
Our main conclusion regarding enzyme feed additives is that a direct ruminal effect of the enzymes is improbable at the suggested application rates with these diets:
gas responses were too low, and the enzyme activities added were insignificant in comparison with the enzymes already present in the feedstuffs or ruminal microorganisms. This does not eliminate adaptive, or pre or postruminal effects. More experiments need to be carried out to focus on these aspects, particularly prefeeding storage times and conditions. Finally, the results demonstrate that microbial enzyme activity limits the rate of fiber digestion by ruminal microorganisms.
The plant fiber itself does not limit the fermentation rate, at least when presented in the small particulate form used here, and direct stimulation of cellulolytic
ruminal microbes and their enzyme activities would be expected to benefit the nutrition of ruminants receiving corn or grass silage-containing diets.