Relationship between paraoxonase-1 activity and lipid mobilisation in transition dairy cows.

The objectives of this study were to investigate the influence of the transition period on lipid mobilisation and paraoxonase-1 (PON1) activity, as well as the relationship between the indicators of lipid metabolism and PON1 activity. Twenty-four Holstein-Friesian dairy cows (aged 2-7 years) were included in the study. Parameters of lipid metabolism (triglycerides, total cholesterol, HDL-C, NEFA and BHB) and PON1 activity were monitored on days -30, -10, -2, 0, 5, 12, 19, 26 and 60 relative to parturition. Triglyceride concentration was significantly decreased from parturition until day 60 after calving, as compared to the values obtained before calving (P<0.05). Both total cholesterol and HDL-C concentrations significantly decreased at calving, with an increase during lactation (P<0.05). Serum NEFA concentrations significantly increased at calving (P<0.05) and stayed at the highest values up to day 19 after calving. Serum BHB concentrations increased significantly after calving on days 12 and 19 (P<0.05), which may be a consequence of increased NEFA around parturition. These changes indicate fat mobilisation from adipose tissue due to the energy deficit during the transition period. Serum PON1 activity decreased at calving but increased significantly on days 26 and 60 postpartum, suggesting a reduced antioxidant status in the postpartum period. Additionally, PON1 significantly positively correlated with total cholesterol (r = 0.42) and HDL-C (r = 0.49) and inversely correlated with NEFA (r = -0.33). The results suggested that PON1 activity is related to lipid metabolism and lipomobilisation syndrome and could be considered as a putative marker for metabolic and inflammatory-related disorders in transition dairy cows.