Dr. Agustin Rius 



Dr. Agustin G. Rius

Associate Professor




ANSC 330/338 - Comparative Animal Nutrition 

ANSC 431 - Comparative Nutritional  Biochemistry and Metabolism 

ANSC 531- Comparative Nutritional Biochemistry and Metabolism 



2506 River Drive
235 Brehm Animal Science Building
Knoxville, Tennessee 37996
Phone: (865) 974-3150
Fax: (865) 974-7297
email: arius@utk.edu 
Dr. Rius Lab Website 





Ph.D., Virginia Tech, Dairy Science, 2009

M.S., University of Illinois at Urbana-Champaign, Animal Science, 2004

D.V.M. La Plata National University, Argentina, 1996

Appointment: 60% Research | 40% Teaching

Professional Interest: Ruminant nutrition (Dairy)


Collage of pictures for Dr. Rius 

The overall goal of my research program is to understand the role of nutrients, hormones and regulatory mechanisms of key metabolic pathways to increase nutrient use efficiency in growing and lactating animals. This goal is pursued at molecular, tissue, and animal level with funding driving specific research projects.

My recent research has had a strong focus on nitrogen, because pastoral farming can result in substantial nitrogen cycling. Dairy cattle, in particular, can increase nitrogen pollution because 70% or more of the nitrogen intake is excreted in urine and feces and ultimately to the environment. Indeed, nitrogen species are potent air, water, and soil pollutants. Nutritional and physiological aspects of ruminant digestion contribute to the relatively low efficiency of dietary nitrogen conversion to milk protein. For example, rumen microbes rapidly convert dietary protein into ammonia to sustain microbial growth but a large fraction of this is absorbed, metabolized to urea, and lost in the urine. Under typical feeding conditions, manipulation of rumen protein degradation, which affects efficiency of nitrogen use in the rumen, is an effective strategy to reduce nitrogen losses.

Most of the nitrogen loss occurs in the splanchnic tissues (e.g. liver, intestine) but the magnitude of this loss is variable and not well understood. Amino acids that are not removed by peripheral tissues are recycled to the liver and oxidized. Consequently the extraction of amino acids in the splanchnic tissues has a critical influence in the nitrogen use efficiency. In addition, the poor capture of amino acids to sustain milk protein synthesis is also partially responsible for this inefficiency. For example, manipulation of nutrients and hormones (e.g. amino acids, glucose, and insulin) can modulate capture of amino acids in the udder to sustain milk protein production and reduce amino acids recycling to the splanchnic tissues. Hence, the goal of my research program has been to understand the regulation of protein synthesis in postabsorptive tissues to improve nitrogen use efficiency and reduce waste in dairy cattle.

Nutrient use efficiency is reduced in cows experiencing heat stress because nutrient digestion and postabsorptive energetic metabolism are altered. Heat stress is associated with increased concentrations of urea in plasma presumably due to inefficient incorporation of rumen ammonia into microbial protein, increased muscle catabolism, or lowered energy use efficiency for milk synthesis. Protein synthesis is a highly regulated process mediated by the mTOR signaling cascade which has been targeted with metabolites and hormones (e.g. lysine, glucose, insulin) to maintain protein synthesis in different tissues. This concept positions the mTOR signaling cascade as potential target for interventions to improve nitrogen efficiency in growing and lactating animals. My current research focus is to understand the adaptation of metabolically active tissues and metabolic pathways that affect protein synthesis and catabolism in heat-stressed animals.

To this end, I have been pursuing scientific approaches to conduct basic and applied research aiming at:

  1. Understanding nutritional and hormonal regulation of protein synthesis in different tissues.

  2. Elucidating mechanisms through which heat stress reduces nutrient use efficiency.

  3. Improving use efficiency of nutrients by manipulating digestion and metabolism of dietary components.

To address these goals my research has used in vivo and in vitro studies and a combination of physiological measurements (e.g. milk yield), metabolomics (e.g. stable isotope studies), and genomics (e.g. gene expression analyses). Ultimately, data generated in these and future studies will be used to improve mathematical models and nutritional recommendation in ruminants. Efforts to improve use efficiency of nutrients are of agricultural significance and will reduce on-farm costs and waste benefiting both the industry and the environment.

Selected Publications

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