Impact of Supplemental Energy on Nitrogen Conservation Mechanisms of Amino Acid and Nucleoside

Energy is first limiting for growth in ruminants fed high quality forage whilst nitrogen (N) is in excess of requirements. Therefore, supplying supplemental energy will provide the necessary fuel for efficient N metabolism and growth in cattle consuming high quality forages. The proposed experiments will test the hypotheses that, by providing supplemental energy to a high quality forage diet, we will: 1) enhance the capture of N in the rumen as well as increase the demand for recycled N both in the rumen and lower digestive tract 2) increase the net absorption of amino acids, decrease the proportion of absorbed amino acids that are oxidized as an energy source, and increase the potential for more efficient tissue gain, and 3) increase amino and nucleic acid transporter gene expression. Altering the route of energy supplementation will allow us to determine interactions of luminal vs. metabolic events that are currently unpredictable. Thus, successful completion of this project will provide data for robust prediction models for feeding paradigms to enhance production efficiency, and reduce negative environmental impacts of grazing ruminants.