Some parameters of water-electrolyte metabolism and acid-base balance of dairy cows during pasture and winter season.

The seasonal variations of some components of blood plasma and urine of 150 clinically healthy dairy cows of black-and-white lowland breed aged 3-12 years were investigated. At the end of winter season the increase of bicarbonate, sodium and potassium levels in blood plasma was found. The excretion of sodium and potassium by kidney was several times lower at the end of pasture season than before. The specific gravity of night urine did not change significantly in annual cycle. However significant differences between groups breeding in various regions of the country were stated. The correlation between the specific gravity of urine and the amount of sodium excreted by kidney was the highest and is showed high coincidence in both seasons.