Fibrolytic enzymes increase fiber digestibility and growth rate of steers fed dry forages

Seventy-two steers (289 kg) were offered ad libitum cubed alfalfa hay, cubed timothy hay, or barley silage supplemented with incremental levels of xylanase (IU) and cellulase (FPU), combined in a ratio of 1 IU:0.04 FPU. For alfalfa hay, low and moderate levels (900 to 4733 IU kg(-1) DM) increased weight gain by up to 30% (P < 0.10), whereas, for timothy hay, the highest level (12 000 IU kg(-1) DM) improved gain (P < 0.10) by 36%. No response to enzymes was observed for barley silage. Fibrolytic enzymes improve weight gain of cattle but optimal enzyme levels depend upon the type of forage.