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ME-equivalent value of feed enzymes varies with dietary nutrient concentrations for broilers . Keying

ME-equivalent value(MEV) of feed enzymes is important for the formulation of diets supplemented with enzymes. Whether MEV of an enzyme product is constant or varies with dietary nutrient concentrations(DNC) is not yet known. In this study, a two-factor D-saturated optimization regression design with six treatments was used to measure MEV of a complex feed enzyme product (CFE) in the diets of various DNC for broilers. CFE consisted of amylase (2400U/g), beta-amylase (20000U/g), beta-glucanase (5800U/g), protease (3800U/g), cellulase (1700U/g), xylanase (4600U/g) and pectinase (55000U/g). Basal diet was formulated with corn, soybean meal and extruded soybean to contain on as-fed basis (DM86.9%) ME 12.55 MJ/kg, CP 20%. Ground rice hull was used to dilute the basal diet to formulate diets with 5.0%, 8.0% and 11.5% lower in ME,CP and amino acid contents than basal diet. The doses of CFE in diets ranged from 0% up to 0.23%. 360 1d-old Avian male broilers were randomly allotted into the 6 treatments with 4 replicates of 15 birds each, and were fed ad libitum until 42 days old. Then 8 birds per treatment were selected for a 4-d metabolism trial, during which excreta were completely collected for measuring nutrient utilizations. Bodyweight gain and feed efficiency were improved quadratically (P<0.01) as DNC increased, and so did the utilizations of dietary energy, protein and dry matter. Performance and nutrient utilizations responded quadratically (P<0.01) to the doses of CFE, and reached peak when CFE dose was 0.1%. ME-equivalent value(MEV) of CFE was calculated by the difference of measured ME of diets with vs. without CFE supplementation at the same DNC. When CFE was included in diets at 0.1%, its MEV was 173, 343, 451 and 586 MJ/kg respectively for the diets of control, and 5%, 8% and 11.5% lower in DNC compared to control. It is concluded that MEV of feed enzymes varies with dietary nutrient concentrations.