Sodium, Potassium and Chloride Homeostasis in Cows during Pregnancy and First Months of Lactation

Growth and development of the fetus, preparation of mammary gland for lactation, reproductive system regeneration after parturition and preparation of an organism for new fertilization and pregnancy, force adaptive changes, both morphological and functional, in pregnant and lactating cow. This may result in variations in concentration of minerals in blood. That is why it is very important to monitor changes in concentration of main electrolytes of body fl uids, such as sodium, potassium and chlorides, and resulting blood plasma osmotic pressure. Maintenance of water-electrolyte homeostasis, both during pregnancy and postpartum period, is essential to keep mother’s health and to maintain proper development of embryo/fetus and newborn calf. According to many authors, homeostatic mechanisms, in healthy adult cows are effi cient enough and concentration of sodium, potassium, chlorides in blood is maintained within relatively narrow frames. However, depending on physiological condition – for example during pregnancy or period of intensive milk production, large variations may be observed. Nevertheless, these changes usually does not exceed fairly broad limits of reference values. Relative stability of osmotic pressure, during last month of pregnancy and fi rst month of lactation, despite variations in concentration of electrolytes, indicate effi ciency of mechanisms controlling osmotic stability and electroneutrality of extracellular fl uid.