Transition Cow Metabolism In Relation To Plane Of Energy Prepartum
Transition dairy cows face unique metabolic challenges with increased use of energetic substrates from mobilization of body tissue as a hallmark of this adaptation. This change is characterized by a dramatic drop in the circulating insulin concentrations with the onset of milk production and is accompanied by a significant reduction in circulating insulin concentration which may be exacerbated by insulin resistance on the receptor and post-receptor level. Feeding strategies for dry cows have continuously evolved over the last decades and increasing evidence suggests that overfeeding of energy has detrimental effects on the ability of the dairy cow to successfully accomplish this transition, reflected in increased concentration of markers of negative energy balance postpartum. However, it is unclear if dry period plane of energy has direct effects on systemic or local insulin sensitivity in the peripartum period that hamper the metabolic adaptation of the transition cow. The objectives therefore were to 1) evaluate the effect of three different dry period feeding strategies on markers of energy balance and colostrum and milk production 2) evaluate the effect of different feeding strategies on systemic glucose tolerance and insulin response 3) evaluate the effect of different feeding strategies on adipose and muscle tissue accretion and loss as well as tissue-specific insulin signaling. Cows overfed energy during the prepartum period were at higher risk of hyperketonemia and had elevated concentrations of serum nonesterified fatty acids postpartum, whereas milk production remained unchanged. Colostral IgG concentration was highest in cows fed a controlled energy diet prepartum. Whole body glucose tolerance was unaffected by plane of energy prepartum whereas resting concentrations of insulin and glucose remained more stable during the transition period in cows fed a controlled energy diet. Insulin signaling in muscle and adipose tissue was not affected by dry period feeding and overfeeding did not lead to overt inflammatory changes in adipose tissue. Overall, feeding a controlled energy diet prepartum was associated with favorable metabolic parameters in the absence of changes in early lactation milk production. Changes in glucose tolerance or insulin signaling in peripheral tissues did not provide an explanation for the underlying metabolic mechanisms.
Dairy cow; Energy prepartum; insulin
Warnick,Lorin D; Overton,Thomas R; Wakshlag,Joseph J.
Ph.D. of Veterinary Medicine
Doctor of Philosophy
dissertation or thesis