Chemical Composition and Digestion Kinetics of ... - icdd@uaf.edu.pk

Growth PerformanceDirect fed exogenous enzymes may improve the growth performance of ruminants byimproving the efficiency feed utilization, but the results are inconsistent. Iwaasa et al. (1997)applied an enzyme product (Xylanase B, Biovance Technologies Inc., Omaha, NE) to a 95%barley based finishing cattle diet and observed improved efficiency of feed utilization by 12%which was due to better digestibility that was 5% higher than control. Zahiroddini et al. (2004)observed 4.8% higher average daily gain (ADG) in steers fed enzyme-treated whole crop barleysilage. McAllister et al. (1999) reported 10% increase in ADG in response to the addition of anenzyme product (Finnfeeds Int. Ltd.,Marlborough, U.K.) @ 3.5 L/t of DM to both the forage(ryegrass silage; 30% of the diet) and grain (barley, 70% of the diet) portions of the diet.However, ZoBell et al. (2000) reported no effect on weight gain when the same enzyme product(Finnfeeds Int. Ltd., Marlborough, U.K.) was added to a high-grain barley-based feedlotfinishing diet containing 17% forage (DM basis). While, Zinn and Salinas (1999) reported 6%higher ADG in steers fed diets treated with fibrolytic enzymes. Addition of enzymes improvesthe NDF digestibility and thereby enhances the DM intake and growth performance (Zinn andSalinas, 1999).The variability in growth performance in response to direct fed enzymes might be relatedto differences in enzyme levels in the diets. Beauchemin et al. (1995) observed increased averagedaily gain (24-30%) and improved digestibility in beef cattle fed alfalfa hay with lower levels ofenzyme (0.25 to 1mL/Kg of DM) and reported that higher level of enzyme (2 and 4mL/Kg ofDM) were not that effective.Method and Level of Enzyme ApplicationCertain factors like level of enzyme used, method adopted for enzyme application andphysiological stage of the animal can determine the effect of enzyme application on the animalperformance. Excessive or insufficient supplementation of exogenous enzymes may result inunaltered responses. Nsereko et al. (2002) noticed a quadratic trend in total ruminal bacterialcounts in response to increasing level of an enzyme from Trichoderma longibrachiatum appliedto the dairy cattle ration. However, Jalilvand et al. (2008) concluded that responses towardsenzyme addition level are dependent upon forage type.31