Acid-base, electrolyte and oxidative status in dairy cows at different stages of the production cycle

Abstract

Previous studies in the field of acid-base and oxidative status in cows have mainly focused on the transition period (three weeks before and three weeks after calving). The aim of this study was to determine the differences in the parameters of acid-base and oxidative status and electrolyte balance in cows not only during the transition period, but also at other stages of the production cycle. Holstein-Friesian cows were divided into four numerically equal groups (n = 6): early lactating cows (9?2 days in milk - DIM), peak lactating cows (50?5 DIM), late lactating cows (170?10 DIM) and dry cows (10?1 days before calving). Venous blood samples were taken from the cows to analyze acid-base status, electrolyte concentrations and oxidative stress parameters, and to compare group means. Significantly higher pH was observed in early lactating cows than in late lactating cows. Sodium (Na+) concentration was significantly lower in early lactating and peak lactating cows compared to dry cows, while chloride (Cl-) concentration was also lower in late lactating cows compared to dry cows. Plasma glutathione peroxidase (GSH-Px) activity was higher in early lactating cows compared to peak lactating cows. Thus, the highest blood pH, lowest Na+ and Cl- concentrations and highest serum GSH-Px activity were observed in early lactating cows compared to other groups, indicating the highest metabolic and oxidative stress during this period. In conclusion, it would be useful to consider the inclusion of these parameters in standard health assessment procedures in intensive dairy production.