In vitro gas production and dry matter degradability of a high concentrate diet: influence of exogenous enzymes level

Abstract Text: This study was conducted to evaluate the influence of an exogenous enzyme mixture on <i>in vitro</i> gas production (GP), <i>in vitro</i> dry matter degradability (DMD), metabolizable energy (ME) and short chain fatty acid (SCFA) production in growing lambs fed a high concentrate diet (219 g/kg CP), made with ground sorghum (550 g/kg), alfalfa hay (150 g/kg), soybean meal (220 g/kg), fishmeal (35 g/kg), salt (20 g/kg) and a mineral/vitamins premix (25 g/kg). ZADO® (ENZ) is a powdered, commercially available multi-enzyme feed additive produced from <i>Ruminococcus flavefaciens</i>. Four levels of ENZ (i.e., 0, 5, 10 and 20 mg/g DM; or E0, E5, E10 and E20, respectively) were applied directly to the substrate inside the incubation bottles before addition of buffer medium and rumen fluid, and the treatments were assayed by triplicate in three runs for different weeks. Bottles were incubated at 39 °C for 96 h. The volume of gas produced was recorded at 2, 4, 6, 8, 10, 12, 24, 48, 72 and 96 h after inoculation. A mathematical model was used for estimate lag time, asymptotic gas production and rate of gas production. DMD was determined at end of incubation by filtration of the residue. ME and SCFA were calculated. Data were analyzed as a randomized design and linear and quadratic effects were calculated at P< 0.05. Addition of ENZ linearly increased (P< 0.05) GP at 6 (74.5, 81.1, 83.7 and 87.5 ml/g DM) and 96 h (334.1, 336.1, 338.5 and 346.8 ml/g DM) of incubation and tended (P= 0.08) to linearly increase GP at 12, 48 and 72 h of incubation. Asymptotic GP (334.7, 336.6, 339.1 and 347.3 ml/g DM) was increased linearly (P= 0.05) as the level of ENZ increased and the lag time decreased linearly (2.34, 2.12, 1.78 and 1.73 h) (P= 0.003). Concurrently, DMD (709, 809, 820, 843 g/kg, repectively) increased linearly (P< 0.001) as the level of ENZ increased, but level of ENZ had no effect on SCFA and ME. Finally, level of ENZ had no influence on rate of gas production. Results suggest that this enzyme preparation has potential to improve efficiency of utilization of high concentrate diets fed to growing lambs.

Keywords: Enzymes, degradability, gas production.