Evaluating the Effect of Feed Mixing and Sampling Methodologies on Nutrient Analysis and the Inclusion of a Novel Protease in Broiler Diets

Abstract

Proper poultry feeding requires a homogenous mixture of macro and micro ingredients to ensure feed nutrients are being supplied to meet bird requirements. Samples of complete feed may be taken during manufacture and analyzed for nutrient content in order to estimate if nutrients are present in feed in accordance to diet formulation. However, variables associated with mixing and feed sampling may influence the results of nutrient analysis, thus over or under estimating the formula comparison. The objective of this study was to vary mix time, sample location, sample number, and sample blending technique on nutrient analysis. Ingredients were mixed in a single screw vertical mixer for either 30 seconds or 10 minutes. Samples were taken from either the pellet die or from the finished feed post cooling, conveyance, and bagging. Samples were blended together from two or 10 samples during manufacture. Blending occurred from either combining samples and mixing by hand or using a sample splitting device. Proximate analysis and free supplemental DL-methionine and L-lysine-HCl were determined on each blended sample and standardized for moisture content. A preliminary study was performed to determine mixer coefficient of variation and showed that ingredients were homogenous when a corn-salt mix was utilized and mixed for 10 minutes (P<0.05). In the primary study, crude fat and free supplemental DL-methionine were affected by mix time (P<0.05). The 10 minute mix time produced values for crude fat and free supplemental DL-methionine that were lower and higher, respectively, compared to the 30 sec mix time and agreed more with the calculated nutrient profile and diet formulation. Free supplemental DL-methionine was also affected by sampling location (P<0.05). Samples obtained at the pellet die were higher and agreed more with the calculated nutrient profile compared to finished feed samples obtained at the sack off bin. Total ash was affected by a sampling location and sampling technique interaction (P<0.05). Samples collected at the pellet die were in closer agreement regardless of sample number; whereas, finished feed samples obtained at the sack off bin were affected more by sample number. These data suggest that mixing and sampling variables can effect nutrient analysis and sampling protocols should be utilized to best estimate if nutrients present in feed are in agreement with diet formulation. The particular conditions of the study suggest that analysis of free supplemental DL-methionine from samples obtained at the pellet die may be the best metric for determining pelleted diet homogeneity and accordance relative to diet formulation. Exogenous enzymes added at the mixer should demonstrate activity post-pelleting and improve bird performance to justify use in the broiler industry. Past research has shown that diet substrate and the pelleting process can effect enzyme efficacy. The objective of the study was to evaluate the feeding value of a novel protease in unprocessed mash and pelleted diets that were composed of all v...