Amino acid digestibility reduction in heat-damaged meat and bone meal fed to broiler chickens and growing pigs

When pigs and beef cattle are processed in a slaughterhouse, the inedible parts are often used to produce meat and bone meal, which is a valuable supplement for pigs and chickens. However, the production of meat and bone meal requires heating, which can reduce the amino acid (AA) digestibility of this byproduct in pigs and chickens. Therefore, the objective of the current study was to determine the effects of species, heat damage, and interaction between these factors on standardized ileal digestibility (SID) of AA in meat and bone meal. To simulate heat damage, meat and bone meal samples derived from the same batch were autoclaved at 134 °C for 0 to 180 min. Experimental diets consisted of a nitrogen-free diet and 7 diets in which each sample of meat and bone meal was the sole nitrogen source. An interaction between species and a quadratic effect of autoclaving time was observed (P < 0.05) in the SID of AA except for tryptophan, aspartate, glycine, and proline (Table 5; Figure 1). Specifically, a quadratic decrease in the SID of arginine was only observed in growing pigs, whereas a quadratic response was only observed in the SID of the other AA in broiler chickens (interaction; P < 0.05). Broiler chickens had greater (P < 0.05) SID of aspartate and glycine compared with growing pigs. The SID of nitrogen, tryptophan, aspartate, glycine, and proline linearly or quadratically decreased (P < 0.05) with increasing autoclaving time in both species. Considering the differences in AA digestibility between broiler chickens and pigs in response to the severity of heat damage, target species should be considered when using the SID of AA values of meat and bone meal in diet formulation.