Nutritional & Digestive Physiology

Michael S. Allen, Professor
Principal Investigator, Digestive Physiology Laboratory
David G. Main, Laboratory Coordinator

Our research team studies the relationship between digestion characteristics of feeds and energy intake, efficiency of microbial protein production in the rumen, partitioning of metabolic fuels and milk production. Digestion characteristics of feeds affect the amount, type and temporal variation of metabolic fuels absorbed, and nitrogen utilization by ruminal microbes and the animal. Temporal variation in absorbed metabolic fuels affects meal size (determined by satiety) and intermeal interval (determined by hunger), which together determine feed intake as well as partitioning of energy to adipose tissue and the mammary gland. Our overall goal is to maximize efficiency of nutrient utilization by ruminant animals with emphasis on nitrogen while formulating diets to maintain animal health.

Adam Lock, Assistant Professor
Ruminant Nutrition, Nutritional & Digestive Physiology, Lactation Biology) Courtney Preseault, Laboratory Manager & Research Technician

Research in the Lock lab focuses on the regulation and manipulation of ruminant lipid metabolism, allowing improvements in the efficiency of animal production and providing opportunities to design foods that are consistent with consumer perceptions and dietary recommendations. Of particular interest is the effect of diet on the production of bioactive fatty acids in the rumen, their subsequent impact on metabolism and milk fat synthesis in the mammary gland and applying this knowledge to improve our ability to troubleshoot on farm issues related to milk fat depression. The impact of milk on human health, in particular the role of milk fat, is also of special interest.

Nathalie L. Trottier, Associate Professor
Non-ruminant Nutrition Laboratory

The overall objective of my research program is to study factors affecting and regulating amino acid utilization in animals. To accomplish this objective, we have focused on three major areas. The first area is the estimation of amino acid requirements of non-ruminants species at different stages of production. In this area, my primary focus is lactation both in the pig and the horse. Our approach to determine amino acid requirements during lactation uses a combination of the traditional milk amino acid profile as well as mammary amino acid uptake profile. More recently, in collaboration with Drs. Brian Nielsen, John Shelle and Christine Skelly, I have begun testing various approaches to estimate protein requirements of the exercising horse. My second area of research involves the study of factors controlling the availability of amino acids for milk production. In this area we have examined aspects such as dietary protein intake, blood flow, and more recently, in collaboration with Dr. Jeanne Burton, whether amino acid transport processes pose a limitation on milk protein synthesis. To accomplish the later, we are using a combination of kinetic and molecular approaches to identify and characterize amino acid transport systems and proteins. We hope that the information generated will provide major advances in our understanding of the regulatory mechanisms for milk protein synthesis and the efficiency of amino acid utilization by the mammary gland. My third area of research focuses on the optimization of dietary amino acid utilization to lessen environmental nitrogen losses. Because nitrogen (N) and ammonium (NH4+) are major components of agricultural waste contributing to environmental pollution, the optimization of dietary amino acid utilization during growth or other productive functions has become one of my research priorities. There is discrepancy between studies on growth performance, body composition, and nitrogen status in animals fed reduced crude protein diets to limit nitrogen losses. We are currently focusing on identifying the factors that pose a limitation on dietary crude protein reduction. Better understanding of the dietary manipulations that can reduce nitrogen losses and maintain production efficiencies is needed to assist in designing nutrient management plans.

Michael J. VandeHaar, Professor
Ruminant Metabolism Laboratory
Jim Liesman, Research Associate

My research program includes dairy nutrition and mammary physiology, replacement heifer nutrition and management and nutrition modeling. The major research focus is to identify mechanisms by which nutrition alters mammary development of dairy heifers with emphasis on leptin and the insulin-like growth factor system.