## 2 Materials and Methods
### Meat Production
#### 3.1.3 Lipid Oxidation of Poultry Meat  
Despite poultry meat having many nutritional characteristics appreciated by the consumer, the interest in the relatively high content of PUFA in the muscle has led to research on dietary manipulation which may increase the unsaturated fat content of muscle membranes [31]. This change, however, increases the susceptibility of poultry meat to lipid oxidation [32]. Several papers have tested PFA in comparison with different doses of VitE to assess their effectiveness in delaying lipid oxidation in poultry meat samples stored under different conditions. In order to demonstrate the antioxidant activity in meat products, thiobarbituric acid (TBA) analysis is used to measure malondialdehydehehyde (MDA), which is a product of meat oxidation that increases during storage [33]. A significant reduction in MDA values in refrigerated breast (up to 47%) and thigh meat (up to 30.2%) samples was observed in broilers receiving GP (at 1.5, 3, and 6%) compared with those consuming a basal diet [23; 34]. The same effect was found in breast (by 22.4%) and thigh (by 62.3%) muscle (raw and warm tissue) when broilers were fed with a commercial blend of essential oils (Apacox(r), APA-CT, Italy: APA; 0.01 and 0.05% of the diet) [35]. Moreover, addition of HE (0.15 or 0.3% of the diet) in broilers' diets reduced (on average, by 41.15%) the MDA content in raw pectoralis muscle after 9 days of storage [13]. Dietary supplementation with RL (0.57 to 1.15% of the diet) and RO (0.010 to 0.020% of the diet) for 42 days decreased the MDA content (on average, by 27.3 and 25.5%, respectively) in broiler meat when measured over 5 days post-mortem compared with VitE (50 and 200 mg/kg) supplementation [18]. A combination of essential oils (0.015% of both RO and OO diets) compared with VitE reduced the MDA value (up to 53.7%) and delayed lipid oxidation of breast and thigh samples at the end of the 15 days of storage [17]. The dietary inclusion of OO alone (0.5% of the diet) or in combination with VitE (170 mg/kg) or VitC and VitE simultaneously (190 and 170 mg/kg, respectively) did not affect the MDA values, although the antioxidant capacity of the raw and cooked meat was improved [36]. The administration of RPO (1% of the diet) and VitE (200 mg/kg) reduced MDA values in broiler breast meat after 14 days of preservation compared with the inclusion of different dose rates and additive combinations (RPO, 0, 0.5, or 1.0% of the diet; and/or VitE, 0, 100, or 200 mg/kg) [14]. A combination of essential oils (0.015% of both RO and OO of the diet) was as effective as VitE in preserving the sensory qualities of breast meat after 15 days of storage [17]. Moreover, the addition of OO (0.010% of the diet) to a broiler diet was as efficient as VitE (200 mg/kg) in reducing MDA values in samples of breast meat during a 9-month storage period at \(-20\)\({}^{\circ}\)C [37]. Similar findings were observed in stored samples of broilers' IL and liver when their diet was supplemented with OP (3% of the diet) or vitamins (VitC, 1000 mg/kg; and VitE, 200 mg/kg) during a 42-day period [27]. Grape polyphenols (GPP) added at different levels in broiler diets (0.0025 to 0.0075% of the diet), compared with VitE (100 mg/kg), increased free radical scavenging activity in breast and leg muscles (from 4.8 to 14%). Total phenolic content increased (by 20.4 and 17.6%, respectively) and thiobarbituric acid reactive substances (TBARS) decreased (by 18.2 and 16.7%, respectively) in breast and in leg muscle [24; 38]. The inclusion of tomato pomace (TP; 30%) compared with VitE in broiler diets decreased the TBARS value of the meat (by 23.0%) after 4 days of storage [39]. In turkeys, both dietary supplementation with OO (at 0.2% of the diet) and VitE (200 mg/kg) delayed lipid oxidation in breast, thigh, liver, and heart tissues to the same extent [40]. Moreover, a synergistic effect was observed when OO (0.1% of the diet) and VitE (100 mg/kg) were added simultaneously.