A rumen linear programming model for evaluation of concepts of rumen microbial function

A linear programming model provides for analysis of general input-output relationships in the rumen, for evaluation of competitive relationships among rumen microbes, and for computation of optimal relationships in the rumen. Eight rumen microbial groups defined on the bases of substrate specificity, nutrient requirements for growth, fermentation products, and relative metabolic activities comprise the central core of the model. Relative metabolic rates of microbial groups calculated from their cell sized were used as coefficients in the objective function. The model was used to evaluate effects of different amounts of protein from feed and various carbohydrates upon microbial population and fermentation patterns as accommodated by current concepts. During the several solutions of the model, considerable simplification of the rumen microflora occurred. This implies that current data and concepts, and the hypothesis regarding relative metabolic rate, as represented in the model, do not accommodate adequately competitions among the several rumen microbial species and, thus, that additional data and concepts regarding rumen microbial interactions are required. Also evaluated were effects of ingestion of bacteria by protozoa upon over-all rumen function, absolute microbial cell yields, cell yields per mole of adenosine triphosphate, and factors affecting these.