Serum paraoxonase-1 activity of dairy Holstein-Fresian cows in different lactation stages--preliminary study.

The objective of this study was to investigate paraoxonase-1 (PON-1) activity in different lactation stages. The study was conducted on Holstein--Friesian dairy cows in 2nd and 3rd lactation. A significant decrease in paraoxonase activity was found in the postpartum period and during peak of lactation. Serum triglyceride and cholesterol concentration were also markedly reduced during postpartum period. The concentrations of uric acid in serum was 23% higher during lactation peak in comparison with dry and postpartum period. The results indicate that lower serum paraoxonase activity and higher concentration of uric acid are associated with oxidative character of transition period and lipid functional antioxidative protection during intensive milk production.