Poultry meal, a rendered byproduct of poultry slaughter, is a valuable protein source in swine and poultry diets because of its highly digestible protein content and balanced amino acid (AA) profile. Rendering of poultry meal may reduce its AA digestibility because of heat damage to the byproduct. The effect of heat damage on AA digestibility of poultry meal may be different between broiler chickens and growing pigs. For this reason, the objective of this study was to determine the effect of autoclaving time on standardized ileal digestibility (SID) of AA in poultry meal fed to broiler chickens and growing pigs. Poultry meal from the same batch was autoclaved at 134 °C for 0, 30, 60, 90, 120, 150, or 180 min to produce seven heat-treated samples. Eight experimental diets were formulated. Poultry meal served as the sole source of nitrogen in seven diets that each contained one of the heat-treated byproducts and a nitrogen-free diet was formulated to assess basal ileal endogenous losses of AA. In experiment 1, 656 male broiler chickens (initial body weight = 719 ± 97 g) at day 18 post hatching were assigned to the eight diets in a randomized complete block design with body weight as a blocking factor. On day 23, birds were euthanized by CO2 asphyxiation and dissected for the collection of ileal digesta. In experiment 2, 16 barrows (initial body weight = 23.3 ± 0.7 kg) were surgically fitted with T-cannulas at the distal ileum and allotted to a duplicate 8 × 4 incomplete Latin square design with the eight diets and four periods. Each experimental period consisted of 5-day adaptation and 2-day ileal digesta collection periods. Data for experiments 1 and 2 were pooled and analyzed as a 2 × 7 factorial treatment arrangement with the effects of species (i.e., pigs and broiler chickens) and autoclaving time (i.e., 0 to 180 min) as the two factors. Increasing autoclaving time decreased SID of nitrogen and all AA in both species, but the decrease in SID values except for leucine was greater (interaction, P < 0.05) or tended to be greater in pigs compared with broiler chickens. Given the species differences in AA utilization response to the severity of heat damage, target species should be considered when using SID of AA values of poultry meal in diet formulation.
Keywords: amino acid; autoclaving; broiler; digestibility; poultry meal; swine.
Poultry meal, a rendered byproduct of poultry slaughter, is a valuable protein source in swine and poultry diets. Rendering is required during the processing of poultry meal to inactivate potential harmful bacteria and to reduce moisture content in the raw byproduct. However, rendering can induce heat damage to poultry meal, which may reduce amino acid (AA) digestibility. To mimic heat damage to poultry meal, the byproduct was autoclaved at 134 °C for 0, 30, 60, 90, 120, 150, or 180 min in the current study. These seven heat-treated poultry meal samples were then fed to broiler chickens and growing pigs. AA digestibility in poultry meal decreased with increasing autoclaving time, but the decrease in digestibility of most AAs by autoclaving was larger in growing pigs compared with broiler chickens.
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