In today’s busy world we often forget some of the classic research papers that created our knowledge base that provided the foundation for the feed industry we know today. This research was conducted over 30 years ago and still is a guiding principal to understanding soybean meal quality.
Researchers at Texas A&M University conducted an experiment to compare four soybean meals (SBM) that were processed in a commercial solvent-extraction plant to give a much wider range in heat treatment than is found among commercially available SBM. The meals were designated in ascending order of heat treatment as Under, Normal, Over and Rumen Escape. The Normal meal was processed using standard commercial operating conditions. The Under meal received less heat treatment by both reducing the steam pressure and retention time in the desolventizertoaster. Over and Rumen Escape meals received further heat treatment in an additional four compartment toaster. The Over meal received less heat treatment than the Rumen Escape meal by reducing steam pressure and retention time in both toasters.
Results indicated crude protein content was similar for the four meals, but lysine tended to decrease with increasing heat treatment. In general, urease activity, trypsin inhibitor, protein dispersibility index and nitrogen solubility index decreased with increasing heat treatment. In studies with calculated pigs they found the apparent ileal digestibility of nitrogen and amino acids were similar for all meals (P>.05); however lysine digestibility for the Rumen Escape meal was lower compared to the average of the lesser-heated meals. Energy digestibilities and nitrogen balance data were also similar (P>.05) for the four meals. The researchers concluded that there were no differences in nutritional value among the Under, Normal and Over meals, which represent the range in heat treatment usually found among SBM. The Rumen Escape meal, which received more severe heat treatment, tended to have lower nutritional value than the lesser-heated meals. (Note: This research supports the conclusion that normally processed commercial soybean meals are of uniform quality; Consistent quality is an important trait of soybean meal that promotes greater use in commercial feeds).