Abstract
Blood gases, electrolytes, and metabolites assist clinicians and researchers with disease diagnosis and prognosis, and can inform treatment decisions on farms. Delays between sample collection and processing can lead to significant changes in these parameters, affecting their clinical and biological value. Therefore, the objective of this study was to evaluate the stability of selected blood gas, electrolyte, and metabolite measurements in dairy cattle whole blood samples stored at 4°C, in addition to frozen plasma samples stored at -80°C for different storage periods. Multiple blood samples were collected from Holstein lactating dairy cows (n = 10) and preweaning heifer calves (n = 16) at a commercial dairy farm in New York state at a single time point. Samples were analyzed using a blood gas analyzer for sodium (Na), potassium (K), chloride (Cl), ionized calcium (iCa), ionized magnesium (iMg), pH, bicarbonate (HCO(3) (-)), base excess (BE), anion gap (AnGap), glucose (Glu), lactate (Lac), creatinine (Creat), and BUN. One blood sample was analyzed within 30 min after collection to provide baseline values. The remaining 6 samples were stored at 4°C and analyzed after 8, 12, 24, 48, 72, and 168 h. After baseline analysis, the first sample was used to collect plasma samples. The plasma baseline was immediately analyzed, and the 2 aliquots were stored at -80°C for analysis after 2 and 4 wk. The effect of storage time on blood gases, electrolytes, and metabolites was analyzed separately for whole blood and plasma using linear mixed-effects models for each individual blood parameter. Blood concentrations of iCa, iMg, and Creat remained stable during storage at 4°C for up to 168 h. Measurements of pH, Na, K, Cl, Glu, Lac, BUN, BE, and AnGap changed over time, with greater differences observed after 48 h for Glu, BUN, and BE compared with the baseline. Although statistical differences were observed for pH and Na at 24 h, values remained within the normal range until 48 h. The K and Lac were identified as the least stable parameters and underwent significant changes after 8 h. We conclude that bovine whole blood samples can be analyzed for electrolytes, blood gases, and metabolites within 48 h postcollection without significant clinical changes, if well stored and refrigerated at 4°C, except for K and Lac. Plasma samples, however, provide stable and reliable measurements for K and Lac for up to 4 wk of storage at -80°C; the results agree with whole blood concentrations.