Models of prediction and methods of estimation of the production of microbial protein in the rumen.

The microbial protein in the rumen is expressed in the yield or the efficiency of synthesis and is related with the quantity of energy in the ATP form used during such process, the quantity of substrate fermented or the available nitrogen in the rumen. These two measures are going to be affected by the rate of growth of the microorganisms and by the factors that influence on the microbial synthesis. The trust of the models of prediction of the microbial protein synthesis is increased by taking into account the factors that influence on the microbial synthesis. However, it results to be risky extrapolatein the experimental results to real situations of production, thus, models should be developed according to the results obtained in such conditions. To attain estimates that can be trusted of the production of microbial protein, it has been developed the not invasive method of the puric derivatives as microbial markers measured in the urine. The combination of the technique of in vitro gas production as microbial markers or with the determination of the truly degradated substrate and the called factor of partition are other forms of estimate the efficiency of microbial synthesis. The results obtained has been restricted, due to limitations of such methods. Moreover, the majority of the models have been developed in conditions of template countries (breed of the animals, feeding and climate), which reduce their possibilities of application in the tropic. It is presicely in this region where it is made more necessary the search and evaluation of new sources of feeds. Before this reality, it is imposed to search new challenges in the development and application of in vitro methods that, combined to molecular techniques, permit elucidate the mechanisms from the microbial interactions and predict in vivo processes. [ABSTRACT FROM AUTHOR]