Autoclaving time-related reduction in metabolizable energy of poultry meal is greater in growing pigs compared with broiler chickens

The objective of this study was to determine the energy utilization responses of growing pigs and broiler chickens to poultry meal that was autoclaved at 134 degrees C for 0 to 180 min. Poultry meal from the same batch was autoclaved at 134 degrees C for 7 autoclaving times of 0, 30, 60, 90, 120, 150, or 180 min to generate 7 samples. Eight experimental diets consisting of a basal diet based on corn and soybean meal, and seven test diets in which 15% of energy-contributing ingredients in the basal diet were replaced with each of the seven poultry meal samples were used. In experiment 1, there were 64 barrows (initial body weight = 19.4 +/- 1.0 kg) allotted to 8 experimental diets in a randomized complete block design with body weight as a blocking factor. Each pig received an experimental diet during 5 d of adaptation followed by 5 d of quantitative total, but separate, collection of urine and feces. In experiment 2, a total of 512 male broiler chickens at day 17 post-hatching (initial body weight = 660 +/- 80 g) in 8 replicate cages were allotted to 8 experimental diets in a randomized complete block design with body weight as a blocking factor. Excreta were collected from days 20 to 22 post-hatching, and birds were euthanized by CO2 asphyxiation for ileal digesta collection. Data from experiments 1 and 2 were pooled together for statistical analysis as a 2 x 7 factorial treatment arrangement with the effect of species (pigs or broiler chickens) and autoclaving time of poultry meal (7 autoclaving times between 0 and 180 min). An interaction between species and their linear effect of autoclaving time was observed (P < 0.05) in metabolizable energy (ME) of poultry meal. Specifically, linear decrease in ME values in poultry meal with increasing autoclaving time was greater (P < 0.05) in growing pigs (4,792 to 3,897 kcal/kg dry matter) compared with broiler chickens (3,591 to 3,306 kcal/kg dry matter). The ME value of unautoclaved poultry meal was greater (P < 0.01) for pigs than broiler chickens at 4,792 vs. 3,591 kcal/kg dry matter. Although decrease in ME values with autoclaving time of poultry meal was greater in growing pigs than in broiler chickens, the ME in autoclaved poultry meal fed to pigs was greater than ME in non-autoclaved poultry meal fed to broiler chickens. Furthermore, the ratio of cysteine to crude protein concentration is a potential indicator for estimating the ratio of ME to gross energy in poultry meal for growing pigs (r(2) = 0.81) and broiler chickens (r(2) = 0.84). Given the species differences in energy utilization response to severity of heat damage, target species should be considered when using metabolizable energy value of poultry meal in feed formulation. Lay Summary Poultry meal is a rendered product that consists of clean flesh and skin-derived from the parts of whole carcasses of slaughtered poultry. Because poultry meal has a highly digestible protein concentration and optimal amino acid profile, it is widely used in swine and poultry diets. During the rendering process, poultry meal is heated, which may affect energy utilization. In the current study, poultry meal was autoclaved at 134 degrees C for 0, 30, 60, 90, 120, 150, or 180 min to mimic heating of poultry meal. These seven poultry meal samples were fed to growing pigs and broiler chickens. Reduction in energy utilization with autoclaving time of poultry meal was greater in growing pigs compared with broiler chickens. However, despite a larger decrease in energy utilization in poultry meal by autoclaving in growing pigs, metabolizable energy values were still greater in growing pigs compared with broiler chickens.

Automated summary

The objective of this study was to determine the energy utilization responses of growing pigs and broiler chickens to autoclaved poultry meal. The results showed that autoclaving time had a significant effect on the metabolizable energy of poultry meal, and the decrease in energy utilization was greater in growing pigs compared to broiler chickens. However, even with a larger decrease in energy utilization, the metabolizable energy in autoclaved poultry meal fed to growing pigs was still higher than in non-autoclaved poultry meal fed to broiler chickens. The ratio of cysteine to crude protein concentration could be used as a potential indicator for estimating the energy utilization in poultry meal.