Relationship between the parity and oxidative stress in high-performance Polish Holstein-Friesian cows after the peak of lactation

Relationship between parity and oxidative stress in high-performance Polish Holstein-Friesian cows after the peak of lactation. There are many factors, which may expose cows attacks of free radicals. The highest level of oxidative stress appears in the parturition period and at the peak of lactation. Therefore, the purpose of this study was to demonstrate the relationship between the parity and oxidative stress in high-performance Polish Holstein-Friesian (PHF) cows after the peak of lactation. Seventy PHF cows were selected for the experiment according to: age (35 primiparous and 35 multiparous in the second lactation) and stage of lactation (after the peak of lactation; at days 61–90 in milk). Samples of milk and blood were collected in monthly intervals, from 61st–90th till about 271st day of lactation. Study results demonstrated a signifi cant impact of the parity and days in milk of cows on the formation of oxidative stress markers. The primiparous cows were characterized by lower levels of GluRed and Gpx. The lowest level of oxidative stress was observed in the months after the peak to about 250 days of lactation. Based on study results, it can be concluded that that younger animals were more exposed to free radicals and oxidative stress.