Analysis of correlations between selected blood markers of acid-base balance, blood electrolytes, and milk components in dairy cows during late lactation

The aim of the study was to assess the values of and correlations between selected markers of acid-base balance and electrolytes in the blood of late lactation cows, such as pH, pCO2 , pO2 , HCO3- , BE, BE(B), Na+ , K+ , Cl- , as well as selected parameters of milk, such as the number of somatic cells (SCC), colony forming units (CFU), milk fat (MF), milk protein (MP), milk lactose (ML), milk solids, milk solids non-fat (SNF), and current milk production. Blood and milk samples were collected at the same time from 11 clinically healthy milking cows in the later lactation period. Those 11 selected cows were examined once a day for 3 consecutive days resulting in 33 sets of blood and milk samples used for laboratory and statistical analyses. Significant positive correlations were observed between pH and HCO3- , pH and BE, pH and BE(B), pCO2 and HCO3- , pCO2 and BE, pCO2 and BE(B), HCO3- and BE, HCO3- and BE(B), BE and BE(B), Na+ and Cl- , Na+ and milk production, Cl- and milk production, and Cl- and MP. Significant negative correlations were observed between pH and K+ , pH and Cl- , pCO2 and Cl- , HCO3- and Cl- , BE and Cl- , and BE(B) and Cl-. The increase in blood pH was significantly negatively correlated with the current milk production, while the increase in HCO3- or pCO2 was associated with a significant decrease in the amount of protein in milk. These relations can indicate a significant negative influence of blood acid-base imbalance on the quantity and quality of cow's milk. The repeatable diagnostic model presented here proved to be a very useful tool for a detailed assessment of selected higly sensitive parameters of internal homeostasis in productive dairy cows.