Altering the bed depth in the desolventizer/toaster (DT) used in soybean meal preparation affects protein quality and amino acid digestibility by cecectomized roosters

To determine optimal processing conditions for preparation of a SBM that will result in optimal amino acid digestibilities, six lots of high protein SBM were produced under different toasting conditions. Specifically, the bed depth in the desolventizer-toaster (DT) was varied (11.4, 12.7, 14.0, 15.2, 17.8, and 20.3 cm). All soybeans were acquired from the same producer, and the preparation and extraction conditions were held constant for all lots. Protein quality indices were measured for each of the resultant SBMs. While the protein dispersability index (PDI) values suggested that all SBMs were adequately processed, the protein solubility in potassium hydroxide (KOH) data suggested that the SBMs produced at bed depths less than or equal to 14.0 cm were adequately processed while those produced at bed depths greater than or equal to 15.2 cm may have been overprocessed. The urease activity results, however, suggest that the SBMs produced at bed depths between 11.4 and 15.2 cm were underprocessed, and those at 17.8 or 20.3 cm were properly cooked. The SBMs then were fed to cecectomized roosters in order to determine true amino acid digestibilities by poultry. True digestibilities of histidine, tryptophan, cysteine, and proline increased (P<0.05) with increasing bed depth. All bed depths resulted in relatively high amino acid digestibilities. Producing SBM at a bed depth between 15.2 and 20.3 cm may result in an increased digestibility of some SBM amino acids by poultry.