Effects of an exogenous enzyme, Roxazyme® G2 Liquid, on digestion and utilisation of barley and sorghum grain-based diets by ewe lambs

A study was conducted to determine effects of a predominantly xylanase/endoglucanase exogenous enzyme (EE) product on digestion and production characteristics of growing lambs (25.3 kg) fed barley or sorghum grain-based diets. Dorset cross ewe lambs were allocated within four liveweight (LW) block groups to one of eight treatments (2 × 4 factorial design) comprising either whole barley or cracked sorghum grain diets (630 g/kg, DM basis) treated with one of four levels of a concentrate applied EE (0, 1.22, 4.88 and 9.76 ml/kg ration DM). Dietary digestibility was determined 4 and 8 weeks after EE treatments commenced and the lambs were fed for 84 d (until average LW > 40 kg). Compared with lambs fed barley-based diets, the lambs fed sorghum-based diets had superior (P<0.05) feed conversion to LW (7.13 and 5.80 kg as fed/kg, respectively) and daily wool growth, although average daily LW gain (172 g) was not affected by diet. Supplementing lambs with EE did not change voluntary feed intakes or total tract digestibility of NDF and starch compared to the lambs fed EE untreated diets. Lambs fed the sorghum diet exhibited a linear increase in total tract ADF digestibility with increasing rate of EE treatment and N balance also increased linearly, potentially due to improved ruminal protein availability. However EE supplementation did not improve lamb performance in terms of LW gain, feed conversion efficiency or wool growth.