Louis E. Armentano, Ph.D.

Room 952 Animal Science Building
1675 Observatory Drive
Madison, WI 53706
608-263-3940
armentan@calshp.cals.wisc.edu

Emphasis Groups:
Animal Nutrition
Biochemical & Molecular Nutrition

Principal Research Interest:
Ruminant nutritional physiology, especially in the role of the liver to integrate nutrient transfer among tissues in support of lactation and growth.

Research Summary:
The nutritional physiology of ruminants cannot be interpreted by assuming that regulatory mechanisms are identical to those in non-ruminants.

This laboratory's goal is to define where ruminants possess regulatory mechanisms differing from the generalized models of mammalian metabolism, and to elucidate mechanisms involved. Gluconeogenesis is essential to support milk production. This laboratory has demonstrated a direct and specific inhibition of hepatic propionate and lactate metabolism caused by butyric acid addition to isolated caprine and bovine hepatocytes. By adapting monolayer culture technology to bovine liver, this laboratory determined the direct short-term effects of insulin and glucagon on gluconeogenesis and glycogenolysis in ruminant. Development of insulin resistance in liver was shown as calves aged.

This laboratory has also cooperated in research which demonstrated a low capacity for triglyceride rich lipoprotein synthesis in goats and calves, leading to rapid accumulation of triglyceride during the negative energy balance typical of early lactation. Exposure of hepatocytes to a physiological mixture of long chain fatty acids, with concomitant triglyceride accumulation, did not reduce hepatic
capacity for gluconeogenesis in vitro, but did reduce capacity for ureagenesis.

Recent evidence suggests that lactating ruminants are deficient in methionine, and hepatic catabolism of methionine limits the use of absorbed methionine conversion to milk protein. Enhancing methionine delivery to the mammary gland by reducing hepatic catabolism would increase milk protein synthesis, decrease dietary cost, and decrease generation of waste nitrogen and sulfur. We are currently studying the regulation of methionine catabolism in hepatic monolayers from calves.

Representative Publications:

Leonardi C, Armentano LE. Short communication: Feed selection by dairy cows fed individually in a tie-stall or as a group in a free-stall barn. J Dairy Sci. 2007 May;90(5):2386-9.

Gressley TF, Armentano LE. Effects of low rumen-degradable protein or abomasal fructan infusion on diet digestibility and urinary nitrogen excretion in lactating dairy cows. J Dairy Sci. 2007 Mar;90(3):1340-53.

Gressley TF, Reynal SM, Colmenero JJ, Broderick GA, Armentano LE. Technical note: development of a tool to insert abomasal infusion lines into dairy cows. J Dairy Sci. 2006 Oct;89(10):3965-7.

Gressley TF, Armentano LE. Effect of abomasal pectin infusion on digestion and nitrogen balance in lactating dairy cows. J Dairy Sci. 2005 Nov;88(11):4028-44