## 2 Materials and Methods
#### 3.2.3 Plasma Oxidative Status  
Several studies investigated the effects of PFA on plasma oxidative status markers. Among these, of importance is the superoxide dismutase (SOD), which, along with glutathione peroxidase (GPx), acts as an antioxidant in reactive oxygen species (ROS) balance. Broilers fed with RL (0.57%, 0.86%, and 1.15% of the diet) and RO (0.01%, 0.015%, and 0.02% of the diet) compared with VitE (50 and 200 mg/kg) for 42 days did not show significant differences on SOD activity, whereas the high inclusion levels of RL and RO reduced this parameter [18]. Similarly, no significant effects on broilers' SOD activity were observed in a trial comparing the dietary inclusion of OL with VitE [26]. The dietary supplementation with GP (7.5% of the diet) in broilers reared under thermoneutral conditions increased plasma SOD activity compared with control and VitE (by an average proportion of 50.8%) groups. The dietary supplementation with GP (5% of the diet) compared with basal and VitE diets led to a similar increase of SOD activity but lower in extent. Meanwhile, the dietary inclusion of GP at higher level (10% of the diet) did not improve SOD activity compared with basal or VitE (200 mg/kg) diets [34]. Broilers showed higher GPx activity when fed with GP (5% of the diet) in comparison with those consuming a basal (by 46.3%) diet. Higher doses of GP (7.5% of the diet) compared with basal and VitE diets increased GPx activity (by a mean value of 46.4%), whereas VitE compared with the basal diet did not improve this parameter [34]. The dietary supplementation with OLE compared with a basal diet increased GPx (by 24.0%) but not when compared with a VitE diet [26]. Another parameter investigated to assess the antioxidant capacity of PFA was malondialdehydehyde (MDA), an endogenous marker of lipid oxidation, whose increase is induced by a decreased antioxidant protection capacity of the organism. Several studies reported favorable effects of supplementing poultry diet with PFA on different markers related with the antioxidant status. For instance, the dietary inclusion of OL (0.4% of the diet) compared with VitE and a basal diet reduced MDA values (by 22.5%) in plasma. A reduction of the ferric reducing activity power (FRAP by 19.1%) in broilers fed with OL (0.4% of the diet) compared with VitE was found. However, FRAP was higher (by 26.5%) in broilers fed the basal diet [26]. The GP fed animals (7.5% of the diet) compared with those consuming basal and VitE diets reduced their MDA plasma content (by 25.2%) [34]. A high n-6:n-3 diet (HDR) combined with CBP (0.4% of the diet) lowered MDA content (by a mean proportion of 28.3%) in laying hens compared with basal and VitE diets. The same CBP treatment induced a decrease of hepatic MDA content (by 29.7%) compared with control, low levels of CBP (0.2% of the diet), and VitE diets. When the same animals were fed with a low n-6:n-3 diet (LRD) supplemented with CBP at the high level (0.4% of the diet) compared with those consuming basal, CBP at low level (0.2% of the diet), and VitE, treatments decreased their MDA plasma content (by 24.2% on average). The same group had also the lowest hepatic MDA content (by 13.8%) compared with control, CBP (0.2% of the diet), and VitE. The lower level of CBP dietary inclusion was as effective as VitE in reducing this parameter [50]. The dietary supplementation with CBP at both levels also significantly increased total antioxidant capacity (TAC) independently from n-6:n-3 ratio in the diets (HRD and LRD diets). The HRD fed animals, when supplemented with CBP at both levels, showed higher TAC than those consuming the basal (by 41.5% on average at the two doses) and the VitE (by 17.5% on average) diets. Moreover, the LRD fed animals, when supplemented with the high level of CBP only, showed higher TAC than those fed basal and VitE diets (by 51.0% on average). These results showed that the highest inclusion levels of CBP were more effective than VitE in improving TAC values.