Beauchemin et al. (2003b) reported overall increases
of 1.0 ± 1.3 kg/d in DMI and 1.1 ± 1.5 kg/d in milk
yield with the addition of fibrolytic exogenous enzymes
to dairy cow diets when combining data from 20 studies
and 41 treatments. It is clear from the standard
deviations that responses to adding fibrolytic enzymes
to ruminant diets have been variable. It is therefore not
surprising that the use of fibrolytic enzyme products in
commercial dairy operations has not yet been widely
adopted. However, continuing increases in feed costs
and consumer concerns about the use of growth promoters
and antibiotics in livestock production provide
ample incentive to revisit and refine the use of enzyme
feed additives in ruminant diets as a means of improving
feed conversion efficiency and lowering the cost of
milk production