Relationship Between Electrophoretic Band Patterns and In Vitro Ammonia Release of Soluble Soybean Meal Protein

Sodium dodecyl sulfate gel electrophoresis was used to examine soluble protein fractions extracted with McDougall's buffer from soybean meal treated with various alcohol-water mixtures. Of the identified proteins, conglycinin and acidic subunits of glycinin were affected most by alcohol treatment. Their concentration in the extract was related to alcohol concentration in the treatment solution. In vitro digestion of soluble protein showed that fractions rich in conglycinin released the most ammonia per gram protein whereas treatments resulting in low concentrations of conglycinin and acidic subunits of glycinin produced the least amount of ammonia. Soybean meal treated with 40% (vol/vol) propanol had the lowest ammonia release and lowest conglycinin content. Conglycinin is deaminated faster by rumen microflora than are basic subunits of glycinin. Sodium dodecyl sulfate electrophoresis is a useful method to investigate chemically treated soybean meal and could be helpful in evaluating other protein-rich feeds that are treated to enhance their utilization by ruminants.