Regulation of nitrogen salvage in non-ruminants

猪和其他非反刍动物能够通过尿素循环过程和随后在胃肠道中产生的微生物氨基酸来回收氮。然而，尿素再循环进入肠道的调节机制以及影响尿素再循环和随后氮利用程度的因素（如饮食、生理）尚不清楚。在反刍动物中，除了非特异性的细胞旁运动外，尿素进入瘤胃的运输部分是由于促进性尿素转运蛋白（UT-B和水通道蛋白）。膳食因素，如纤维和蛋白质的摄入，可能通过改变肠道环境和改变动物和常驻微生物的营养供应来影响氮的回收。假设是尿素回收和氮回收是一个受调节的过程，可以通过改变饮食蛋白质和纤维摄入量来控制。目的是确定(i)饲粮组成（如蛋白质和纤维含量）对尿素循环利用程度和循环尿素命运的影响，（ii）尿素通过肠壁运输的机制和调控，（iii）饲粮组成对非反刍动物氮利用的影响，以及（iv）振荡饲粮蛋白质对氮利用和保留的影响。为了实现这些目标，将招募一名博士生，4名硕士研究生和一名学士荣誉论文学生，以猪（一种重要的农业动物物种）完成一系列动物实验。将使用同位素输注、生长性能、氮平衡和体外（例如，乌辛室）技术的组合。该研究计划将为非反刍动物尿素循环和氮回收的调控机制提供新的信息，这将导致新的喂养计划的发展，以提高氮的保留和猪肉生产的可持续性。这个研究项目的目标将有利于我的长期研究目标，即表征饲料成分和动物生理的相互作用，以便更好地了解这些因素对动物生长和健康的营养利用的影响。

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.