ABSTRACT
Soybean meal is the most commonly used protein supplement for ruminants, especially in the United States. In fact, it is the standard to which other protein supplements are compared. Dietary protein entering rumen is either degraded by the rumen microbes to peptides, amino acids, volatile fatty acids and ammonia, and/or it can bypass rumen degradation to be digested and absorbed as amino acids and peptides from the intestinal tract. There are two means of treating soybean protein that have been investigated intensively. The first is the use of formaldehyde to cross link the soybean protein making it unavailable for degradation in rumen. The increase in live-weight gain from increasing levels of protein is a direct measure of the value of the protein. At some point, the protein requirement of the animals is met and no further response to protein is obtained. The amino acid profile of bypass protein is an important criterion in the evaluation of sources for practical diets.
