Enteric fermentation and amino acid economy in pigs

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The overall aim of the proposed research is to better understand the impact of enteric fermentation in the upper gut of mono-gastric animals and humans, on utilization of dietary amino acid (AA) intake for body protein deposition and body maintenance functions. It is hypothesized that enteric microbes (1) contribute to the catabolism of dietary and endogenous AA in the upper gut of mono-gastric animals and humans, and (2) preferentially use preformed AA for the synthesis of microbial protein, even when the host is fed a low protein diet. These hypotheses imply that microbial fermentation in the upper gut contributes substantially to dietary AA requirements in mono-gastric animals and humans. Isotope tracer studies will be conducted to quantify key aspects of AA metabolism in intestinal tissue and enteric microbes, as well as protein digestion in growing pigs. These studies will be complemented with proteomics and transcriptomics to identify and characterize diet effects on mucosal protein profiles and regulation of synthesis of mucosal proteins. The proposed research will yield quantitative estimates of the contribution of microbial fermentation in the upper gut of growing pigs to AA catabolism and net AA supply to the host animal. These estimates will be used to further develop our biology-based, mathematical model that represents nutrient utilization for growth in the pig and that is used to assess the economic and environmental impacts of alternative feeding strategies growing pigs, teach principles of nutrient utilization in education programs, and to explore areas where further research is needed. Improvements in the efficiency of dietary N utilization will reduce the contribution of pigs to environmental degradation and reduce feeding costs associated with protein. Feed, in turn, represents at least 50% of the cost of pork production. The proposed research will provide an excellent opportunity for training two Ph. D. students and further training of a post-doctoral fellow. The findings have applications for the nutrition of all mono-gastric farm animals and humans.