The objective of the present experiment was to quantify the gas production parameters, methane emission and microbial nitrogen production of a conventional total mixed ration including corn silage, alfalfa hay, wheat straw and concentrate (390, 110, 22 and 478 g/kg of diet DM, respectively) treated with different levels of Natuzyme® and pre-incubation time after enzyme administration. Two hundred fifty mg of milled and dried basal diet (n=4) was weighed into a 125 mL serum bottles for an in vitro gas production trial. A solution of a commercial enzyme blend (Natuzyme®) was added at 0, 12 and 24 h prior to starting the in- cubation (96 h) to make treatments of 0.84, 1.68 and 2. 52 g/kg, respectively. No added enzyme bottles were considered as control. Half time of gas production (t 1/2 ) was calculated. Then, another gas test was run for each treatment and terminated at t 1/2 to measure gas volume, methane emission and solid residues. Dose rate of Natuzyme® did not make any significant differences in gas production parameters and fermentation responses except for microbial nitrogen production. Pre-treatment of the basal diet at 24 h incubation sig- nificantly (P<0.05) lowered dry matter degradability and accumulated gas, but percentage and amount of produced methane, produced methane by mg degraded dry matter and microbial nitrogen production was significantly increased. Twelve and twenty four h pre-tr eatment of the basal diet significantly (P<0.05) in- creased accumulated gas by 16% and 8%, respectively. However, fractional constant rate was significantly (P<0.05) decreased by 31% and 13%, respectively, usi ng twelve and twenty four h pre-treatment of the basal diet. However, a specific pre-treatment time must be taken into consideration to allow the enzyme mixture to bind to the feed particles.

Keywords