Subclinical hypocalcemia (SCH) is a disease of significant concern in the dairy industry. Up to 50% of early lactation dairy cows experience this disease and when SCH persists to 4 days postpartum, a negative metabolic state known as dyscalcemia ensues. Dyscalcemia has been consistently associated with compromised immune cell function, reduced reproductive performance4, increased disease occurrence, and suboptimal production later in lactation. Despite these well-established trends, identifying dyscalcemic cows in a cost-effective, timely, and non-labor-intensive fashion remains a major challenge for both producers and dairy practitioners. Efforts to develop point of care devices for blood calcium analysis have been largely unsuccessful, leaving end-point colorimetric lab analysis of serum samples as the only viable option for diagnosis. We aim to provide a solution to this problem.

We believe that excessive inflammation is the underlying driver behind progression of SCH to dyscalcemia in early lactation dairy cows. There is good consensus that inflammatory activation and elevated concentrations of blood inflammatory mediators precede the development of many bovine diseases and are associated with negative downstream outcomes. Overwhelming data strongly correlate inflammation with calcium dysregulation across model species in a variety of disease contexts; however, the specific relationship between inflammatory mediators and SCH has never been established. Elucidating this relationship will reveal diagnostic targets through which SCH progression can be monitored.

Our objective is to evaluate the use of inflammatory mediators as markers of SCH progression. We hypothesize that blood concentrations of inflammatory mediators will be linked to dyscalcemia, such that their concentrations in the blood will be predictive of dyscalcemia and unfavorable SCH progression.

To accomplish this objective, we will describe daily patterns of inflammatory mediators, specifically the acute phase proteins haptoglobin, lipopolysaccharide binding protein (LBP), and serum amyloid A (SAA), in the blood of a cohort of periparturient Holsteins from -1 to +4 days postpartum. Analysis will be performed on banked serum samples from a 2020 field trial in which calcium status, as well as health and production outcomes, have already been described. Haptoglobin and LBP concentrations will be analyzed using commercially available assay kits, while SAA analysis will be conducted at the Animal Health Diagnostic Center at Cornell University. Using linear regression models, we will identify the inflammatory mediators most closely associated with dyscalcemia. Through the evaluation of inflammatory patterns over time, we will determine the optimal diagnostic timepoint at which to measure inflammatory mediators associated with dyscalcemia and go on to use logistic regression models and receiver operating characteristic curve analysis to establish diagnostic thresholds for these mediators. Based on limited previous research, we expect all three inflammatory mediators will be associated with dyscalcemia, i.e., SCH at 4 days postpartum.

The data we collect will not only fill a major knowledge gap in our understanding of the progression of SCH but will also provide a new diagnostic target for dyscalcemia. Because these mediators can all be measured using enzyme-linked immunosorbent assays, a method which lends itself well to the development of cost-effective point of care devices such as SNAP tests, we will leverage our data to attract funding for the development of a novel, cost-effective diagnostic tool for clinicians to use in the field. Inflammatory mediators have been used for quite some time to influence clinical decision making in human medicine. It is time that these techniques are made available to the bovine practitioner to improve health outcomes for poorly adapting dairy cows.