## 2 Materials and Methods
#### 3.2.3 Plasma Oxidative Status
Furthermore, CBD supplementation in the HRD diet increased VitE content in blood in comparison with the basal diet (by an average of 79.5% at the two doses). Nevertheless, only the highest inclusion level of CBP in LRD diet increased VitE level (by 103.0%) [50]. By contrast, when a sweet chestnut wood (SCW) extract was fed to broilers in comparison with high polyunsaturated fatty acids (PUFA; from linseed oil) content diets and two levels of VitE (85 and 200 mg/kg), no significant effects were reported on plasma and liver MDA content, total antioxidant status (TAS), lipid soluble antioxidant capacity (ACL), or SOD and GPx activities [57]. The SCW feeding reduced (by 42.4%) the DNA damage compared only to the linseed oil fed group [57]. In broilers fed with natural tocopherols, roscenary, grape seed, green tea, and tomato alone or in different combinations (0.01% and 0.02% of the diet) among them for 42 days, no significant effects on plasma FRAP, thiobarbituric acid reactive substances (TBARS), or SOD activity were reported. Conversely, some effects were observed on GPx activities [58]. The TAS was not affected by polyphenols (PP) supplementation in broilers' diet in three similar studies [37; 38; 39]. However, SOD activity was reduced in PP (by 18.3%) and PPE (PP with VitE; by 21.8%) fed animals compared with those not exposed to heat stress (thermoneutral). The GPx activity was increased (by 49.1%) in the PPE group compared to those challenged with heat stress [37] as well as in PPE (by 20.5%) and in PP (by 11.9%) groups in comparison with those consuming a low quality oil diet [39]. In this last study, GPx activity was higher in PPE (by 15.0%) and in PP (by 14.3%) fed animals. In another similar study in which all diets contained grain contaminated with ochratoxin A, TAS was greater in PPE (by 23.5%) and PP (by 21.6%) groups than in the positive control group (only grain contaminated) [38]. However, SOD activity was lower (by 18.4%) in PP compared with the control group, which consumed the uncontaminated grain, but was higher (by 10.6%) in PPE than the VitE (100 mg/kg) group and lower in PP (by 12.8%) than the high dose VitE group (200 mg/kg). In the same study, GPx activity was higher in PPE (by 17.6%) and in PP (by 34.6%) than the contaminated grain fed broilers without showing any significant difference with VitE. Among different parameters investigated (VitE, total tocopherols, VitC, retinol) in blood and in liver, hepatic TBARS values were significantly affected. Indeed, they were higher (by 32.0% on average) in PPE and in PP in comparison with the thermoneutral group [37]. Conversely, the supplementation with PPE decreased hepatic TBARS values compared with broilers fed with contaminated grain, demonstrating a synergistic effect of PP and VitE in mitigating the detrimental effects of nutritional stress [38]. Dietary supplementation of chickens with GP (3% of the diet) compared with basal and VitE diets resulted in a higher total intake of extractable polyphenols (by 50.6%) [15]. Digestibility of extractable polyphenols was also higher (on average 117.2%) in GP than in basal and VitE fed animals [15]. Total antioxidant capacity (measured by ABTS assay) of chicken excreta increased (by 19.9%) when fed with GP compared with basal diet. A similar increase (by 18.8%) was found when the TAC was determined by FRAP assay. No difference was observed between VitE and GP treatments in ameliorating this marker [15]. In male broiler chicks, TAC was also affected when GP was included in animals' diets at different levels (1.5%, 3%, and 6% of the diet) [14]. In fact, TAC of diet, ileal content, and excreta were higher (by average proportions of 345.4%, 102.7%, and 41.6%, respectively) in GP than in unsupplemented broilers. Meanwhile, the same parameter was determined to be higher (by a mean of 125.6%) in the diet and the ileum (by an average of 68.2%) in GP than in the VitE (200 mg/kg) fed animals. Furthermore, GP supplementation did not affect the serum TAC (measured by ABTS assay).