RELATIONSHIPS BETWEEEN CARBOHYDRATE NUTRITION AND METABOLISM, INFLAMMATION, AND PERFORMANCE OF DAIRY CATTLE DURING THE PERIPARTURIENT PERIOD
LaCount, Sarah Elizabeth
The transition from pregnancy to lactation is a time of great metabolic adaptations for the dairy cow. Dry matter intake decreases, yet demand for nutrients increase vastly with the onset of milk production resulting in negative energy balance. Cows must mobilize body tissues to increase energy for the body while sparing glucose for the mammary gland. Due to this increased metabolic demand and negative energy balance, cows often end up in a state of metabolic dysfunction which can have disastrous consequences. Nutritional strategies can help increase glucose precursors while decreasing body tissue mobilization that is linked to increased risk of disease. Previous research is mixed on the impacts of high starch to increase glucose precursors to the cow immediately postpartum, likely due to an increased risk for subacute ruminal acidosis that can result in metabolic dysfunction and inflammation. Feeding strategies which utilize high starch while also including higher fiber to promote rumen health have not been conducted. The objectives of this dissertation were to: 1) investigate interplay of fiber fractions in high starch postpartum dairy cow diets on performance, hepatic metabolism and energy balance, 2) examine interplay of inflammation, hepatic metabolism, energy metabolites, and metabolic hormones in the postpartum period, and 3) investigate opportunities to combine use of a higher digestibility corn silage with monensin to optimize production and health in the periparturient period. Increased fiber in the postpartum diet can limit intake in early lactation, resulting in negatively altered metabolism and production. As intake restrictions were eased by feeding a more fermentable diet, cows were able to recover intake, production, and energy metabolites in a matter of days to match cows that were not limited in intake early postpartum. Increased fiber in diets that may pose a higher risk of subacute ruminal acidosis may still be warranted, though further research on fiber levels and fractions is needed. Correlations between improved hepatic metabolism and metabolic hormones indicative of energy balance were positive, though correlations between markers of improved hepatic metabolism and inflammation were negative. Cows fed corn silage with higher digestibility and monensin, which increases glucose precursors, showed a possible synergistic effect on milk production. Using either strategy alone increased energy status, improved metabolism and health status, however a combination of both strategies decreased milk components, indicating they might negatively alter the rumen environment and milk fat synthesis.
dairy cow; starch; transition period; Animal sciences; Dairy cattle; fiber
Overton, Thomas R.
McArt, Jessica Anne Allerton; Van Amburgh, Michael E.; Butler, Walter Ronald
Ph.D., Animal Science
Doctor of Philosophy
dissertation or thesis