# Effect of storage time on the stability of selected blood gases, electrolytes, and metabolite concentrations in dairy cattle whole blood and plasma

## TL;DR

The study found that most blood parameters in dairy cattle remain stable for up to 48 hours when stored at 4°C, but potassium and lactate are better preserved in plasma stored at −80°C.

## Contribution

This study provides new insights into the stability of blood gases, electrolytes, and metabolites in dairy cattle blood and plasma under different storage conditions.

## Key findings

- Whole blood electrolytes, blood gases, and metabolites remain stable for up to 48 hours at 4°C.
- Potassium and lactate are less stable in whole blood but remain stable in plasma stored at −80°C for up to 4 weeks.
- Calcium, magnesium, chloride, anion gap, and creatinine are stable in whole blood for up to 7 days.

## Abstract

Summary: Blood samples (n = 182) were collected from Holstein lactating cows and preweaning heifers (n = 26) at a single time point. One whole blood sample was analyzed as the baseline, and the remaining 6 samples were stored at 4°C for analysis of blood gases, electrolytes, and metabolites at different time points. Additionally, plasma samples were analyzed as baseline, and 2 aliquots were stored at −80°C for analysis. Whole blood measurements of electrolytes, blood gases, and metabolites remained stable for up to 48 hours after collection when stored at 4°C. Potassium and lactate were less stable in whole blood; however, they showed greater stability and agreement in plasma samples. Created in BioRender.

Summary: Blood samples (n = 182) were collected from Holstein lactating cows and preweaning heifers (n = 26) at a single time point. One whole blood sample was analyzed as the baseline, and the remaining 6 samples were stored at 4°C for analysis of blood gases, electrolytes, and metabolites at different time points. Additionally, plasma samples were analyzed as baseline, and 2 aliquots were stored at −80°C for analysis. Whole blood measurements of electrolytes, blood gases, and metabolites remained stable for up to 48 hours after collection when stored at 4°C. Potassium and lactate were less stable in whole blood; however, they showed greater stability and agreement in plasma samples. Created in BioRender.

•Blood samples stored at 4°C can be analyzed within 48 hours without clinical changes.•Calcium, magnesium, chloride, anion gap, and creatinine are stable for up to 7 days.•Potassium and lactate show greater variability over time in whole blood.•Potassium and lactate are stable in plasma and show good agreement with whole blood.

Blood samples stored at 4°C can be analyzed within 48 hours without clinical changes.

Calcium, magnesium, chloride, anion gap, and creatinine are stable for up to 7 days.

Potassium and lactate show greater variability over time in whole blood.

Potassium and lactate are stable in plasma and show good agreement with whole blood.

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 (HCO3−), 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.