Professor

Ruminant Nutrition and Physiology

Research Interests

A more complete understanding of the control of nutrient metabolism in ruminants is central to our objective of optimizing growth and lactation.

The goal of research conducted in my laboratory is to determine factors which constrain the productive efficiency of livestock at the level of nutrient metabolism and to devise methods to circumvent such factors. In essence, we are seeking ways to produce milk and / or meat with fewer inputs. The liver, because of its anatomical positioning, exerts a tremendous influence on the profile and supply of absorbed nutrients which may be used for productive processes. Nutrients must first pass through the liver before they reach tissues where they are used for milk production or muscle synthesis. The degree of nutrient breakdown, or catabolism, by liver potentially limits energy and/or amino acids for animal production. Conversely, adequate synthesis of glucose, proteins, and transformation of other substances by liver is necessary to support efficient production of animal products. Our research approach integrates cell biology, molecular biology techniques and whole animal approaches to understand the processes which determine the fate of metabolizable nutrients with a goal of devising practices/technologies to enhance the efficiency of animal growth and/or milk production. Emphasis is placed on control of liver function and nutrient-gene interactions in late gestational and lactating dairy cattle and replacement heifers. Other research interests include: regulation of neonatal development, regulation of adipose tissue metabolism, effects of metabolic modifiers on nutrient partitioning, nutritional endocrinology, insulin resistance, evaluation of alternative feed ingredients, postruminal protein supply, and nutritionally related metabolic disorders.

Video - Research involving distillers' grains

Research Techniques

• Hepatocyte and adipocyte cell isolation and culture
• Molecular biology techniques
• In vivo and in vitro nutrient metabolism
• Radioisotope tracer techniques
• Nutrient analysis of feed ingredients

Selected Publications

Donkin, S.S., G.A. Varga, T.F. Sweeney and L.D. Muller. 1989. Rumen-protected methionine and lysine: Effects on animal performance, milk protein yield, and physiological measures. J. Dairy Sci. 72:1484-1491.

Donkin, S.S. and L.E. Armentano. 1993. Preparation of extended in vitro cultures of bovine hepatocytes that are hormonally responsive. J. Anim. Sci. 71:2218-2227.

Donkin, S.S. and L.E. Armentano. 1994. Regulation of gluconeogenesis by insulin and glucagon in the neonatal bovine. Am. J. Physiol. 266:R1229-R1237.

Donkin, S.S. and L.E. Armentano. 1995. Insulin and glucagon regulation of gluconeogenesis in preruminating and ruminating bovine. J. Anim. Sci. 73:546-551.

Donkin, S.S., A.D. McNall, B.S. Swencki, J.L. Peters, and T.D. Etherton. 1996. The growth hormone-dependent decrease in hepatic fatty acid synthase mRNA is the result of a decrease in gene transcription. J. Mol. Endocrinol. 16:151-158.

Donkin, S.S., P.Y. Chiu, D. Yin, I. Louveau, B. Swencki, J. Vockroth, C.M. Evock-Clover, J.L. Peters, and T.D. Etherton. 1996. Porcine somatotropin differentially down-regulates expression of the GLUT4 and fatty acid synthase genes in pig adipose tissue. J. Nutr. 126:2568-2577.

Buhman, K.K., E.J. Furumoto, S.S. Donkin, and J.A. Story. 1998. Dietary psyllium increases fecal bile acid excretion, total steroid excretion and bile acid biosynthesis in rats. J. Nutr. 128:1199-1203.

Elkin, R.G., Z. Yan, Y. Zhong, S.S. Donkin, K.K. Buhman, J.A. Story, J.J. Turek, R.E. Porter, M. Anderson, R. Homan, and R.S. Newton. 1999. Select 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors vary in their ability to reduce egg yolk cholesterol levels in laying hens through alteration of hepatic cholesterol biosynthesis and plasma VLDL composition. J. Nutr. 129:1010-1019.

Greenfield, R.B., M.J. Cecava, T.R. Johnson, and S.S. Donkin. 2000. Impact of dietary protein amount and rumen undegradability on intake, peripartum liver triglyceride, plasma metabolites, and milk production in transition dairy cattle. J. Dairy Sci. 83:703-710.

Greenfield, R.B., M.J. Cecava, and S.S. Donkin. 2000. Changes in mRNA expression of gluconeogenic enzymes in liver of dairy cattle during the transition to lactation. J. Dairy Sci. 83:1228-1236.

Hartwell, J.R., M.J. Cecava, and S.S. Donkin. 2000. Impact of dietary rumen undegradable protein and rumen protected choline on intake, peripartum liver triacylglyceride, plasma metabolites and milk production in transition dairy cows. J. Dairy Sci. 83:2907-2917.

Hartwell, J.R., M.J. Cecava, and S.S. Donkin. 2001. Impact of rumen undegradable protein and rumen-protected choline on mRNA expression for enzymes in gluconeogenesis and ureagenesis in liver of periparturient dairy cows. J. Dairy Sci. 84:490-497.

Agca, C., R.B. Greenfield, J.R. Hartwell, and S.S. Donkin. 2002. Cloning of bovine liver cytosolic and mitochondrial phosphoenolpyruvate carboxykinase and characterization during the transition to lactation. Physiol. Genomics. 11:53-63.

Hammon, H.M., Y. Zbinden, H. Sauerwein, B.H. Breier, J.W. Blum, and S.S. Donkin. 2003. The response of the hepatic insulin-like growth factor system to growth hormone and dexamethasone in calves. J. Endocrinol. 179:427-435.

Velez, J.C. and S.S. Donkin. 2004. Bovine Somatotropin Increases Hepatic Phosphoenolpyruvate Carboxykinase mRNA in Lactating Dairy Cows. J. Dairy Sci. 87:1325-1335.

Raman, P., S.S. Donkin, and M.E. Spurlock. 2004. Regulation of Hepatic Glucose Metabolism by Leptin in Pig and Rat Primary Hepatocyte Cultures. Am. J. Physiol. Regul. Integr. Comp. Physiol. 286:R206-216.

Agca C., C.A. Bidwell, and S.S. Donkin. 2004. Cloning of bovine pyruvate carboxylase and 5' untranslated region variants. Anim. Biotechnol. 15:47-66.

Velez, J.C. and S.S. Donkin. 2005. Feed Restriction Induces Pyruvate Carboxylase but not Phosphoenolpyruvate Carboxykinase in Dairy Cows. J. Dairy Sci. 88: 2938-2948.

Williams, E.L., S.M. Rodriguez, D.C. Beitz, and S.S. Donkin. 2005. Effects of short-term glucagon administration on gluconeogenic enzymes in the liver of mid-lactation dairy cows. J. Dairy Sci. 89:693-703.

Drackley, J.K., S.S. Donkin, and C.K. Reynolds. 2006. Invited Review. Major Advances in Fundamental Dairy Cattle Nutrition. J. Dairy Sci. 89:1324-1336.