2008 Annual Report 1a.Objectives (from AD-416) 1. Incorporate changes to improve the prediction of wasteful ammonia production in the rumen and assess alternative strategies of reducing nitrogen losses. 2. More accurately describe the impact on energy spilling and pH on microbial growth efficiency and other factors in the model to improve its application to feeding dairy cattle. 1b.Approach (from AD-416) The rumen will be programmed and simulated using an object-oriented language (Stella). This approach will:. 1)estimate ruminal feed degradation and passage from standard methods of feed description,. 2)correct microbial growth efficiency for maintenance energy experiments,. 3)accommodate hyper-ammonia producing bacteria (HAB),. 4)trigger energy spilling when microbial growth is limited by factors other than energy (e.g. ammonia, amino acids or low pH), and. 5)estimate ruminal pH from the amount of VFA generated, VFA dilution from the rumen, ruminal buffering and ruminal mixing motions. Sensitivity analyses will be conducted to identify critical parameters. Coefficients will be adjusted until the outputs from the model closely match results found in the research literature. Milk production will be estimated by linking outputs from rumen model to the animal equations of the Dairy NRC (2001). 3.Progress Report For many years it was assumed that bacteria only had two mechanisms of energy utilization, growth and maintenance. However, research from our laboratory indicated that bacteria could also spill energy via futile cycles of ions through the cell membrane. Energy spilling is triggered when factors other than energy limit growth (e..g nitrogen deprivation and acidic pH), and this wasteful process decreases the amount for microbial protein that would be available to the animal. The process of energy spilling in bacteria was thoroughly reviewed so our forthcoming model of ruminal fermentation will be able to more accurately predict nutrient availability. The ability of most ruminal bacteria to use ammonia as a nitrogen source for growth is a highly advantageous characteristic of ruminal fermentation, but non-fiber carbohydrate (NFC) degrading bacteria typically grow faster and more efficiently if amino nitrogen sources (ruminally degraded protein, peptide or amino acids) are also available. Potential impacts of amino nitrogen on the efficiency of NFC bacterial growth include:. 1)carbon sparing and an increased availability of carbohydrate to generate energy,. 2)an increase in growth rate and a concomitant decrease in the fraction of energy used to maintain the cells, and. 3)a decrease in energy loses (energy spilling). The effect of amino nitrogen sources on bacteria was thoroughly reviewed so our forthcoming model of ruminal fermentation will be able to more accurately predict nutrient availability. A variety of sophisticated modeling languages have been developed, but the most easily used and fully developed program is STELLA. STELLA has many key features:. 1)intuitive icon-based graphical interface that simplifies model building,. 2)stock and flow diagrams that support the common language of systems thinking and provide insight into how the systems work, and. 3)causal loop diagrams that can present overall causal relationships. The software was purchased and installed on all of the collaborators’ computers. I have worked with each individual to make sure that we all understand how to use the software. Several sub-models were created, simulated and evaluated. 5.Significant Activities that Support Special Target Populations None. 6.Technology Transfer Review Publications Russell, J.B. 2007. The Energy Spilling Reactions of Bacteria and Other Organisms. Journal of Molecular Microbiology and Biotechnology. 13:1-11. Xavier, B.M., Houlihan, A.J., Russell, J.B. 2008. The activity and stability of cell associated activity of bovicin HC5, a bacteriocin from Streptococcus bovis HC5. Federation of European Microbiological Societies. 283:162-166. Mantovani, H.C., Russell, J.B. 2008. Bovicin HC5, a lantibiotic produced by Streptococcus bovis HC5, catalyzed the efflux of intracellular potassium but not ATP. Antimicrobial Agents and Chemotherapy. 52:2247-2249.