Serial measurements of circulating glucose and luteinizing hormone concentrations in lactating dairy cattle

The two objectives for this thesis were to 1) validate a bovine luteinizing hormone (LH) ELISA for use in the laboratory and 2) validate interstitial glucose sensors designed for humans for use in lactating dairy cattle. The first experiment required validation of a bovine LH ELISA in order to measure the circulating concentration of LH in the blood of cows in altered thermal and/or metabolic states. Assays from two separate companies were tested. Half of one plate was run at a time resulting in a total of 6 separate analyses (3 plates total). Despite early, promising results, neither LH ELISA could be successfully validated. For many analyses, the standard curves did not even meet the minimal criteria to allow calculation of a formula for determining the concentrations of the unknowns. In analyses where the standard curves were acceptable, the coefficients of variation (CV%) for the unknowns were unacceptable. The second experiment attempted to validate the use of commercially available human interstitial glucose sensors (FreeStyle Libre and Dexcom G6) in lactating dairy cows. Blood glucose concentrations correlated well with sensors secured behind the cow's ear for both FreeStyle Libre (r=0.82) and Dexcom (r=0.88). Unfortunately, however, the absolute relative error's highest value was 47% for the FreeStyle Libre ear. In summary, neither the LH ELISAs nor the interstitial glucose sensors could be validated.