Enzymes, direct-fed microbials and plant extracts in ruminant nutrition

This preface outlines the reasons for the special issue, comments on the review process and provides a brief summary of the papers. Research on feed additives of ‘natural’ or biological origin was provided an impetus due to the European ban on growth-promoting antimicrobial feed additives. However, the potential of feed additive enzymes, direct-fed microbials and plant extracts as beneficial manipulators of ruminal fermentation extends beyond replacement of growth-promoting antimicrobial feed additives in ruminant livestock production to new functions and potential commercial roles.