Effect of pressure processing on amino acid digestibility of meat and bone meal for poultry

In the future, it may become desirable or required to process meat and bone meal (MBM) under pressure to reduce human health concerns associated with bovine spongiform encephalopathy (BSE). Therefore, three experiments evaluated the effects of different processing pressures on the digestibility of amino acids (AA) in MBM when the pressure processing was done after typical rendering (Experiments 1 and 2) or during the initial rendering process of raw materials (Experiment 3). Processing pressures varied from 0 to 60 psi in experimental or commercial feather meal cookers. Increasing pressure during processing reduced MBM Cys concentrations in Experiments 1 and 2. True digestibilities of most AA were significantly decreased by increasing pressures in Experiments 1 and 2, and reductions were generally largest for Cys and Lys, particularly Cys, and increased with severity as pressure increased. For example, in Experiment 1, Cys digestibility decreased from 65 to 50 to 15%, and Lys digestibility decreased from 76 to 68 to 41% as the MBM was processed at 0, 30, and 60 psi, respectively, for 20 min. When the pressure processing occurred during the initial rendering of the MBM raw material (Experiment 3), a significant reduction in digestibility of most AA was observed only at 60 psi, and the decrease was much less than that observed in Experiments 1 and 2. Our results indicate that pressure processing of MBM decreases the digestibility of AA for poultry. Thus, pressure processing of MBM to reduce potential BSE infectivity will likely decrease the nutritional value of the MBM.