The inflammatory status but not the physiological phase affects plasma advanced oxidized protein product (AOPP) concentration in dairy cow.

Advanced oxidized protein products (AOPP) are novel markers of protein oxidation that were first described and characterized in plasma of uremic patients. Their formation is mainly dependent upon chlorinated agents related to neutrophil and monocyte activation, and is thus considered a good indicator of inflammatory response. In addition, AOPP can activate both human monocytes and neutrophils in vitro. The observation that AOPP were higher in plasma of cows affected by embryonic loss in late pregnancy raised our interest in the biological role of AOPP in dairy cattle. The aim of this work was to study the effect of the physiological phase on plasma AOPP concentrations and to assess any possible relationship between AOPP increase and inflammatory status in dairy cows. Plasma concentrations of AOPP, total proteins (TP), haptoglobin (Hp), and WBC counts were determined in 40 healthy dairy cows in different physiological phases (weeks 3-1 before parturition, and weeks 1, 4-6, 16-20 and more than 24 after parturition), and in 23 animals with inflammatory processes such as endometritis, mastitis and lameness. Unhealthy cows were first classified into groups of Acute Inflammation (11 subjects; clinical signs present for less than 3 days) and Chronic Inflammation (12 subjects; clinical signs observed for 3 or more days), respectively; both groups were compared with healthy cows in weeks 1 to 24 after parturition. In healthy animals, plasma Hp concentrations were significantly affected by the physiological phase, plasma levels being higher in week 1 after parturition (P<0.05), as opposed to AOPP. Plasma concentrations of Hp and the AOPP/TP ratio were significantly higher in the Acute Inflammation than in the Chronic Inflammation group (P<0.05), and healthy cows (P<0.001). Finally, animals were allocated on the basis of plasma Hp concentrations into Control (Hp<0.4 mg/ml) and Acute Phase (Hp≥0.4 mg/ml) groups. Plasma AOPP concentrations were significantly higher (P<0.05) in the Acute Phase group, and a significant positive correlation (R2=0.430; P<0.001) between plasma AOPP and Hp was observed. Our results support the hypothesis that AOPP can be used in the bovine as indicators of oxidative stress related to the inflammatory response. As plasma AOPP concentrations seemed unaffected around parturition, they may represent a good marker of the inflammatory status in the post-partum and early pregnancy phases in dairy cows. However, more research is needed to identify the physiological threshold of AOPP concentrations and to assess factors that may influence AOPP concentrations in body fluids.