Animal Nutrition and Feed Technology

Two experiments were carried out to investigate the effect of adding exogenous cellulase enzymes (CE) to a diet for growing lambs on in vitro gas production (GP) kinetics and animal performance. In the first experiment, exogenous CE were added to the diet with rumen fluid 24 h before incubation or at the start of incubation. Compared to the control, CE addition significantly (P<0.05) affected lag time, asymptotic gas production (P=0.05), but the rate of gas production was not affected. The application time of exogenous CE had no significant effect on all the variables studied. In the second experiment, the exogenous CE were sprinkled on the total mixed ration 24 h before morning feeding. Twenty-one Pelibuey lambs (mean BW 15.9±1.6 kg) assigned to two dietary treatments during a 45 d feeding trial in a completely randomized design namely, control or exogenous CE. Total BW and average daily gain were increased (P<0.01) by supplemental exogenous CE, but no effects were observed on lamb's nutrient intake. Supplemental exogenous CE improved (P<0.05) the digestibility of DM, OM, NDF and ADF, but no differences were observed in CP digestibility. Under the conditions of this experiment, the supplementation of exogenous CE has the potential to alter the kinetics of gas production of diets for growing lambs regardless of application time. Further, the supplemental exogenous CE can improve BW gain, nutrient digestibility, and feed conversion efficiency without affecting nutrient intake in Pelibuey lambs.