Relationship between late embryonic mortality and the increase in plasma advanced oxidised protein products (AOPP) in dairy cows

The involvement of protein oxidation in embryonic mortality (EM) has been poorly investigated in cows. Advanced oxidation protein products (AOPP) are markers of protein oxidation generated by activated neutrophils and involved in inflammation. The aim of this work was to study AOPP in cow plasma and their relationship with late EM. The outcomes of 158 artificial inseminations (AI) were examined in 72 cows, which were classified ex post on the basis of blood progesterone and pregnancy-associated glycoprotein concentrations and clinical confirmation of pregnancy into the following categories: (1) positive (AI+, resulted in pregnancy, n = 58), (2) negative (AI-, did not result in pregnancy, n 86) and (3) embryonic mortality (EM, n 14). Plasma protein fractions, malondialdehyde (MDA), total glutathione and AOPP were measured at AI (Day 0) and on Days 15, 28, 35, 45 and 60. MDA was significantly higher in EM than AI+ and AI- animals on Day 45, and than AI+ animals on Day 60 (P<0.05). Mean plasma AOPP concentrations were significantly higher in the EM group (P<0.01) and the ratio of AOPP : albumin was significantly higher in the EM group on Days 15, 28, 45 and 60 (P<0.05). Based on the temporal pattern of the AOPP : albumin ratio, we propose that oxidative stress is implicated in and may possibly be a cause of EM.