Effect of exogenous enzymes on digestibility of barley silage and growth performance of feedlot cattle

Barley silage was sprayed with water or with a 2:1 combination of commercia l cellulase and xylanase preparations, or the enzymes were introduced direc tly into the rumen, in a digestibility study (replicated incomplete 3 x 3 L atin square) using 10 sheep. Apparent digestibilities of dry matter (DM) an d neutral detergent fibre (NDF) were lower (P < 0.05) when enzymes were dos ed intraruminally than when applied to silage, but enzymes by either route did not affect (P > 0.05) intake of DM, organic matter or digestible organi c matter, or digestibilities of DM or NDF, ruminal pH, xylanase activity, e ndoglucanase activity or ruminal cellulolytic bacterial populations. Treati ng the silage portion of an 82.5% barley silage backgrounding diet with the enzyme mix at 0, 1.25, 3.5 or 5.0 L t(-1) DM tended to linearly increase ( P = 0,08) final weights of steers (n = 24). Average daily gain tended to be (P = 0.06) and feed intake and feed efficiency were (P = 0.04 and P = 0.03 , respectively) quadratically related to these enzyme concentrations from d ays 0 to 56, but not overall (days 0 to 120). In contrast, treatment of bot h portions (forage and concentrate) of a 70% barley-ryegrass silage finishi ng diet at 3.5 L t(-1) DM increased (P < 0.01) the average daily gain of fi nishing feedlot cattle by 10%. Carcass weights and traits were not affected (P > 0.1) by enzyme supplementation. In this study, treating the total mix ed ration improved feedlot cattle performance more than treating the silage component alone.