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 commercial cellulase and xylanase preparations, or the enzymes were introduced directly into the rumen, in a digestibility study (replicated incomplete 3 x 3 Latin square) using 10 sheep. Apparent digestibilities of dry matter (DM) and neutral detergent fibre (NDF) were lower (P < 0.05) when enzymes were dosed intraruminally than when applied to silage, but enzymes by either route did not affect (P > 0.05) intake of DM, organic matter or digestible organic matter, or digestibilities of DM or NDF, ruminal pH, xylanase activity, endoglucanase activity or ruminal cellulolytic bacterial populations. Treating 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 days 0 to 56, but not overall (days 0 to 120). In contrast, treatment of both portions (forage and concentrate) of a 70% barley-ryegrass silage finishing diet at 3.5 L t(-1) DM increased (P < 0.01) the average daily gain of finishing feedlot cattle by 10%. Carcass weights and traits were not affected (P > 0.1) by enzyme supplementation. In this study, treating the total mixed ration improved feedlot cattle performance more than treating the silage component alone.