Regulation of nitrogen salvage in non-ruminants

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Pigs and other non-ruminant animals are capable of salvaging nitrogen through the process of urea recycling and subsequent microbial amino acid production in the gastrointestinal tract. However, the regulatory mechanisms for urea recycling into the gut and the factors (e.g., dietary, physiological) influencing the extent of urea recycling and subsequent nitrogen utilization are not well understood. In the ruminant, it has been shown that urea transport into the rumen is due, in part, to facilitative urea transporters (UT-B and aquaporins) in addition to non-specific paracellular movement. Dietary factors, such as fibre and protein intake, may influence nitrogen salvage through altering the gut environment and changes in nutrient supply to the animal and resident microbes. The hypothesis is that urea recycling and nitrogen salvage is a regulated process that can be manipulated through changes in dietary protein and fibre intake. The objectives are to determine (i) the effect of diet composition (e.g., protein and fibre content) on extent of urea recycling and fate of recycled urea, (ii) the mechanism and regulation of urea transport across the gut wall, (iii) effect of diet composition on nitrogen utilization in the non-ruminant, and (iv) the effect of oscillating dietary protein on nitrogen utilization and retention. To address these objectives, a PhD student, 4 MSc students, and a BSc Honours thesis student will be recruited to complete a series of animal experiments in pigs, an agricultural important animal species. A combination of isotope infusion, growth performance, nitrogen-balance, and in vitro (e.g., Ussing chamber) techniques will be used. The proposed research program will provide novel information on the mechanisms regulating urea recycling and nitrogen salvage in the non-ruminant animal which will lead to the development of novel feeding programs to improve nitrogen retention and sustainability of pork production. The objectives of this research program will benefit my long-term research objective to characterize the interaction of feed components and animal physiology in order to better understand the impact of these factors on nutrient utilization for animal growth and health.