Hepatic Energy Metabolism In Early Lactation Dairy Cows
In the period immediately following calving, feed intake is insufficient to support the high milk production of early lactation, resulting in a state of negative energy balance. This state of negative energy balance results in many metabolic adaptations such as the increased mobilization of adipose tissue, manifested as the release of non-esterified fatty acids into circulation to be metabolized by the liver and other tissues and incorporated into milk fat in the mammary gland. Propionate that is produced via fermentation of starch in the rumen is the main precursor for hepatic glucose production, and higher feed and energy intake postpartum generally results in lower circulating non-esterified fatty acids and has been associated with improved health, performance, and less severe postpartum negative energy balance. The objectives herein were to: 1) evaluate the effects of different energetic nutritional strategies on postpartum production and metabolism; 2) evaluate the impact of these nutritional strategies on liver metabolism; 3) evaluate temporal changes in liver metabolism through the transition to lactation and the relationships between hepatic energy substrates; and 4) evaluate the association between the degree of early lactation inflammation with production and metabolism. Cows that were fed diets with greater propiogenic capacity during the postpartum period had improvements in production and metabolism, and increased in vitro conversion of propionate to glucose in the liver. Overall, alterations in fatty acid metabolism that lead to increased triglyceride accumulation during the transition period appear to impair postpartum hepatic gluconeogenesis, and cows that had elevated inflammation in the first week postpartum exhibited a diverse range of production responses, indicating that there is a large degree of variation in individual adaptation.
Transition dairy cow; Hepatic energy metabolism; Nutrition
Brenna,James Thomas; Van Amburgh,Michael E; Nydam,Daryl Van
Ph. D., Animal Science
Doctor of Philosophy
dissertation or thesis