Stress And Inflammation During The Periparturient Period In Holstein Dairy Cows - Associations With Health And Performance And The Influence Of Overstocking
One of the most challenging periods for a dairy cow is during the 3-week period before and after calving. During this period cows undergo several changes in diet, social re-groupings, and dramatic metabolic and physiological adaptations to prepare for parturition and lactation; cows that cannot adapt to these challenges are at increased risk for disease and lower milk yield after calving. The objectives of this research were to: 1) evaluate how physiological parameters associated with stress (plasma cortisol and fecal cortisol metabolites), inflammation (haptoglobin; Hp), and energy metabolism (nonesterified fatty acids: NEFA) measured during the period around calving relate to health status, milk yield and reproductive performance after calving, and 2) identify specific management practices that increase prepartum stress-load and the mechanisms by which health is affected under these conditions. Increased concentrations of analytes related to stress and inflammation measured during the 3 weeks before calving were poor predictors of postpartum disease incidence when compared to increased concentrations of plasma NEFA, a measure of negative energy balance. However, increased concentrations of plasma Hp and fecal cortisol metabolites, particularly during the week after calving, were better predictors of milk yield and reproductive performance than NEFA. Despite it's widespread use in research as a measure of stress, concentrations of plasma cortisol are easily confounded by the stress associated with handling and sample collection; for use in field diagnostics to identify high risk cattle or herds, plasma cortisol is a weak and inconsistent predictor of health and performance. In the second study, overstocking during the dry period was identified as a management practice capable of compromising physiological health. Cattle that were overstocked had greater concentrations of fecal cortisol metabolites and plasma NEFA, and altered energy metabolism as evidenced by reduced glucose clearance rates and an attenuated insulin response to a glucose challenge. Cattle that are the least successful at competing for access to the overstocked feed bunk were at the greatest risk for these metabolic disturbances. The knowledge gained from this research will be used to improve management of cattle around calving to promote health, productivity and overall animal well-being.
Overton, Thomas R
Butler, Walter Ronald; Nydam, Daryl Van; Grant, Richard John
Ph.D. of Animal Science
Doctor of Philosophy
dissertation or thesis