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Primary Audience: Feed Manufacturers, nutritionists, Researchers SUMMARYThe prices of fat and diet formulations with exogenous enzymes have caused a reduction in the amount of fat added to broiler diets. Although diets may be cheaper to produce, there is potential for nutrient and exogenous enzyme destruction with low inclusions of fat (0.5 to 1%) because of frictional heat and shear forces produced in the pellet die. Additionally, much of the added fat may be applied by using postpellet spray application, and the amount of fat added in the mixer may become negligible. Thermal inactivation of exogenous enzymes and the occurrence of unfavorable reactions (e.g., Maillard reaction, protein cross-linking) may be abated by increased levels of fat included at the mixer before pelleting [i.e., mixer-added fat (MAF)]. in this study, we evaluated the effects of MAF (1, 2.5, or 4%) with or without the addition exogenous enzymes (carbohydrase, protease, and phytase), and at different conditioning temperatures (82 or 85°C), on finisher phase feed manufacture, broiler performance variables, and processing yields. increasing MAF reduced the electrical energy usage required to manufacture broiler feed (P < 0.02). Feed intake during the grower and finisher phases and live weight gain during the finisher phase were increased with enzyme addition (P < 0.001). Enzyme addition, conditioning temperature and MAF interacted in their effects on FCR from 23 to 38 d of age (P = 0.009). Overall, enzyme addition decreased FCR, but the effect was greatest with 1% MAF and 82°C or 4% MAF and 85°C. increasing the MAF and conditioning temperature reduced abdominal fat pad yield (P < 0.03). no difference in breast or leg yield was due to any of the factors (P > 0.05). it is likely that increased MAF improved exogenous enzyme retention and nutrient utilization by broilers. Subject to current fat prices, increasing MAF may reduce the total cost of broiler production, particularly when the reduction of electrical energy usage is considered.

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In response to the impending ban on synthetic methionine in organic poultry diets, researchers have focused on finding alternative strategies to supply this amino acid. The objectives of this study were to assess performance and carcass characteristics of broilers fed diets devoid of synthetic methionine by using 1) a slow-growing and a fast-growing genotype, 2) choicefeeding management (supplying grain and a complementary premix in 2 separate feeders), and 3) pasture access and seasonal variation. Inclusion of fish meal and high percentages of soybean meal enabled the specific genotype methionine requirement to be met. All diets were certified organic. The experiment was conducted during the grower and finisher phases in 4 different seasons: late fall, spring, summer, and early fall. Pasture access was assessed either by housing broilers on the West Virginia University Organic farm and giving them outdoor access, or by housing broilers on the West Virginia University Animal Sciences farm and giving them no outdoor access. Fast-growing genotypes were superior in performance and carcass characteristics compared with slow-growing genotypes, and choice-feeding management did not improve performance or carcass characteristics. Pasture access tended to have no effect on slow-growing broilers and decreased the performance of fast-growing broilers. Performance was decreased in late fall, likely because of cold ambient temperatures.

Feed ingredient price has influenced nutritionists to maximize diet nutrient availability through use of exogenous enzymes. Poultry are almost exclusively fed pelleted diets that entails feed being subjected to conditions of high moisture, temperature and pressure that could partially denature added enzymes. Exogenous enzyme efficacy may be decreased or completely lost if enzymes are not able to survive the pelleting process. The objective of the current studies was to properly assess the efficacy of a commercially available exogenous enzyme cocktail subjected to increasing steam conditioning temperatures during pelleting (82, 88, 93 o C). Dietary treatments consisted of nutritionally adequate diets or Positive Control (PC), diets reduced in metabolizable energy (ME) and available phosphorous (AP) or Negative Control (NC), and NC diets with the exogenous enzyme. Study 1 established significant differences between the PC and NC diets (P<0.05). However, the exogenous enzyme cocktail did not improve performance. Study 2 was designed to improve the opportunity for the exogenous enzyme cocktail to demonstrate a benefit. This study utilized increased mixer-added fat addition in the diet formulation that may decrease frictional heat production in the pellet die, and a decreased metabolizable energy difference between the positive and negative control. Again, performance differences were observed between the PC and NC (P<0.05), with no beneficial effect demonstrated for the exogenous enzyme at any temperature (P>0.05). In Study 3, diet formulations were similar to Study 2; however, conditioning temperatures were decreased (71, 77, 82 o C), a thinner die was used for pelleting and an additional unconditioned mash (UCM) treatment was added. Enzyme efficacy was demonstrated for live weight gain and feed conversion ratio (FCR) for UCM (P<0.05) as well as FCR for the 82 o C diets (P=0.07). Performance observations in Study 3 were supported by nitrogen corrected apparent metabolizable energy (AMEn) data. Overall, these studies suggest that future evaluations of enzyme cocktail thermostability and subsequent efficacy should consider several manufacturing variables.

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