Microbial cells formed as a result of rumen digestion of carbohydrates under anaerobic conditions are a major source of
protein for ruminants. They provide the majority of the amino acids that the host animal requires for tissue maintenance, growth
and production. In roughage-fed ruminants, micro-organisms are virtually the only source of protein. Therefore, the knowledge
of the microbial contribution to the nutrition of the host animal is paramount to developing feed supplementation strategies for
improving ruminant production. While this factor has been recognised for many years, it has been extremely difficult to determine
the microbial protein contribution to ruminant nutrition.
The methods generally used for determining microbial protein production depend on the use of natural microbial markers such as
RNA (ribonucleic acid) and DAPA (diamino pimelic acid) or of radioisotopes 35S, 15N or 32P. However, the need to use post-ruminally
cannulated animals and complicated procedures to determine digesta flow are major limitations.
