engleski

Serum paraoxonase-1 activity and nonesterified fatty acid concentration in relation to the resumption of ovarian activity in postpartum dairy cows

Objectives: The resumption of ovarian activity after calving is closely related to the severity of negative energy balance (NEB) and inflammatory response in the early lactation of dairy cows. Thus, the aim of the study was to evaluate nonesterified fatty acids (NEFA) concentration and paraoxonase-1 (PON1) activity related to the resumption of ovarian activity in postpartum dairy cows. Materials and Methods: A total of 24 Holstein dairy cows were included in the study. The cows were assigned into two groups according to gynecological examination (rectal palpation and ultrasound examination) and progesterone (P4) concentration: (1) ovulatory cows (n=11) which resumed ovarian activity within 60 days after calving ; and (2) anovulatory cows (n=13) which did not resume ovarian activity during the same period. Blood samples were taken on days 5, 12, 19, 26 and 60 postpartum. Serum P4 was measured by the immunoassay on Immulite 2000 analyzer (Siemens Healthcare Diagnostics, Germany) ; NEFA concentration was measured by Randox NEFA kit on biochemical analyzer SABA 18 (AMS, Rome, Italy) while high-density lipoproteincholesterol (HDL-C) concentration was assayed by the method based on selective inhibition of the non-HDL fractions by means of polyanions on Beckman Coulter AU 680 (Beckman Coulter Biomedical Ltd., Ireland). The PON1 activity was measured by the spectrophotometric assay using paraoxon as a substrate on Beckman Coulter AU 680. Statistical analysis was performed by SAS 9.3 Software. Results are shown as least squared means with 95% confidence interval. Results: Serum NEFA concentration was significantly higher (P<0.05) in anovulatory cows postpartum (0.7 mmol/L) in comparison to the cows which resumed their ovarian activity within 60 days after calving (0.48 mmol/L). Anovulatory cows had significantly lower (P<0.05) PON1 activity after calving (228 U/L) than cows which resumed the ovarian activity postpartum (339 U/L). Accordingly, HDL-C concentration was significantly lower (P<0.05) in anovulatory cows after calving (1.8 mmol/L) compared to the cows which resumed the ovarian activity within 60 days postpartum (2.7 mmol/L). Conclusions: Lower PON1 activity and higher NEFA concentration in anovulatory cows could indicate oxidative stress and inflammatory responses presenting a higher risk for decreased ovarian activity and thus lower reproductive efficiency of dairy cows after calving. Since serum PON1 is associated to HDL particle, lower HLD-C level in anovulatory cows might suggest the remodeling of HDL particle due to oxidative stress and inflammation. However, further studies are needed to elucidate the roles of PON1 and NEFA in decreased ovarian activity in postpartum dairy cows.

paraoxonase-1; oxidative stress; ovarian activity; puerperium; dairy cows

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