DELINEATION AND PREVENTION OF IMMUNE DEPRESSION AND DISEASE DUE TO DYSREGULATION OF CALCIUM HOMEOSTASIS AND METABOLIC SYNDROME IN DAIRY COWS

In the dairy cow, much of the susceptibility to disease and ~75% of disease incidence occurs near the transition period and are directly or indirectly related calving and the shift from non-lactating to lactating animal and the related problem of hypocalcemia and severe negative energy balance (NEB). It is critical to delineate the physiology underlying the integrative systems that result in hypocalcemia and severe NEB and the pathways that lead from these problems to depressed immune function, subsequent health problems, and poor reproductive outcomes. The major goals of this project are the following: 1) To identify the factors/signals that create and subsequently correct the hypocalcemia and NEB that occurs during the early postpartum period in dairy cows. 2) To determine the pathways that lead from hypocalcemia and metabolic syndrome to the immune system depression and periparturient disease that occurs in some lactating dairy cows. 3) To reduce postpartum hypocalcemia and NEB by inducing the mechanisms that increase appetite and activate calcium mobilization prior to parturition and evaluating effects on post-partum disease and immune system markers. The overall objective of this research proposal is to elucidate the physiological mechanisms that result in hypocalcemia and NEB in periparturient dairy cows that result in depressed immune function, increased post-partum disease, and negative reproductive outcomes. Our central hypothesis is that the demand by the mammary gland for nutrients to synthesize milk, specifically calcium and energy, results in a homeorhetic shift in the dam to support lactation, resulting in increased incidence of hypocalcemia and dramatic changes in body condition, depressed immune function resulting in postpartum disease, such as metritis and mastitis, and poor reproductive success.Our specific objectives for the research project are the following:Objective 1. Establish the role of inhibition of calcium prepartum on postpartum hypocalcemia, immune function, and disease.Objective 2. Determine the contribution of body condition loss during the periparturient period on postpartum immune function and disease.Objective 3. Identify the risk factors and predictive markers, such as colostrum quality and neutrophil function, for metritis, mastitis, and other health events during early lactation in high-producing lactating dairy cows on commercial dairies.The importance of the present proposal is that the most important physiological reasons for dairy health problems are being addressed at both the in-depth physiological level and the practical level on commercial dairy farms facilitating future research to focus on predicting and rationally preventing and treating these health problems.