Effects Of Exogenous Enzymes On Feed Nutrient Metabolic Rate In Roosters Under Different Force-feeding Amounts

Enzymic preparations, which are generally considered as green feed additives, canimprove diet digestibility, mitigate excreta pollution, promote animal growth, etc. Theefficiency of dietary enzymes is affected by many factors, such as diet types, processing andstorage conditions and supplemental dosages. Currently, researchers mainly focused on thebenificial effects of exogenous enzymes, but enzymes might function differently amongranging dry matter intake (DMI) levels, which was usually ignored. Therefore, anempting-force feeding method was used to evaluate the dietary nutrient metabolic rates ofcaecectomized roosters with different feed intake levels, and the relationship between DMIand enzyme supplementation was also investigated. Fifty-four roosters closed in weights wererandomly divided into9treatments with6replicates per treatment, and1rooster per replicate.One treatment acted as endogenous metabolic group, the remaining eight treatments werearranged to a4×2completely randomized design, in which four force-feeding levels (15,20,25and30g/kg BW, respectively) and two enzyme levels (0and500mg/kg) were performed.According to our results, the apparent metabolic rates of dry matter (DM), energy andcrude protein (CP) as well as apparent metabolizable energy (AME) were significantlyincreased with the increasing of force-feeding levels (P<0.001). However, the truemetabolizable energy (TME) and the true metabolic rates of DM, energy and CP were notaffected (P>0.05). In addition, dietary enzyme supplementation tended to improve feed AMEand TME (P=0.084and P=0.065), and30g/kg BW showed the best effect, where AME andTME were increased by2.30%and2.12%respectively. The percentage increments of feednutrient metabolic rates were gradually improved with the force-feeding level rised from20g/kg to30g/kg, while this regulation was not found at the15g/kg.These results indicated that the effect of enzyme was improved following the increase offorce-feeding amount, thereby feed intake should be considered in poultry industry tooptimize enzyme supplementation.