## 2 Materials and Methods
### Meat Production
#### 3.1.3 Lipid Oxidation of Poultry Meat
Although VitE (200 mg/kg) was more effective in reducing TBARS values and increasing the resistance against oxidation of the abdominal fat in broiler meat samples after 9 days of storage, RL administration was able to reduce (by 57.2%) and increase (by 32.6%) the above parameters, respectively, in comparison with the basal diet [22]. Moreover, VitE (150 mg/kg) was more effective than magold xanthophyll (MX; 0.002% of the diet), CE, TE, and SE (0.056% of the diet each) in reducing TBARS values (by 25.2%) and delaying lipid oxidation in broiler meat samples [19]. Tea catechins from green tea leaves (GTL, Camellia sinensis; 0.3% of the diet) significantly delayed lipid oxidation to the same extent as VitE (200 mg/kg) in frozen chicken thigh meat for up to 9 months of storage [50]. In another study by the same authors, it was found that catechins (at 0.3% of the diet) were superior to VitE (200 mg/kg) in improving the oxidative stability of chicken thigh meat [51]. Conversely, dietary GTL compared with VitE (200 mg/kg of the diet) increased TBARS values (by 213%) in thigh meat [16]. The dietary addition of tomato skin and orange peel (0.2% each), for 56 days in broiler diets, was as efficient as VitE (200 mg/kg) in reducing TBARS levels in leg meat. In ducks, orange peel and RL decreased TBARS values (by 71.0 and 33.0%, respectively) in breast meat, but not as much as VitE (by 82%), compared with the basal diet; however, in legs, orange peel and RL supplementations were at least as effective as VitE in reducing (by 66.0, 47.0, and 46%, respectively) TBARS values [16]. Therefore, dietary supplementation with GP, HE, APA, OO, OP, and RO can reduce MDA levels in poultry samples under refrigeration, and sometimes as effectively as VitE. In some cases, a synergistic effect between PFA and synthetic vitamins (VitE and VitC) was reported, allowing a reduction in the levels of synthetic vitamins added to the diets of poultry. Dietary supplementation with PP alone (0.02%) or in combination with VitE (0.01% of PP + 100 mg/kg of VitE) in comparison to receiving only an ochratoxin-contaminated and low-antioxidant diet decreased TBARS values (by 55.3% and 42.6%, respectively) in broiler breast muscles [15]. However, this difference in TBARS values was not observed when the comparison was made with VitE supplementation [12]. In another trial, consumption of the same product (at 0.02% of the diet) did not affect TBARS values in the BM of broilers fed with low-quality oil [28]. On the contrary, the TBARS levels were decreased (by 82.7%) when the animals were fed PP and VitE simultaneously. In summary, many in vivo studies demonstrate that PFA dietary inclusion can delay lipid oxidation in poultry meat under different storage intervals. These effects were often lower than those exerted by VitE or at least equivalent when PFA were fed at the highest doses. Moreover, a synergistic effect between PFA and synthetic vitamins has been shown, introducing the possibility of reducing the inclusion level of synthetic vitamins in poultry diets when needed, as in the case of organic livestock systems.