## 2 Materials and Methods
### Meat Production
#### 3.1.1 Slaughter Traits (Carcass Weight and Quality, and Internal Organ Weights)
A significant increase (by 3.9%) in hot carcass weight (HCW) was found when the broiler diet was supplemented with TO (at 0.02%) compared with VitE (100 mg/kg), whereas a decrease in HCW (by 4.7%) was observed at lower levels of TO (0.01% of the diet) or higher levels of VitE (200 mg/kg) inclusion [21]. Liver weights of TO-fed broilers were lower (on average, by 12.0%) than those receiving VitE (200 mg/kg) [19]. A greater pancreas and liver weight in the RL group than in the control (by 21.5 and 18.6%, respectively) and VitE groups (by 27.6 and 18.2%, respectively) has been reported [22]. In grape pomace (GP, 1.5%)-fed broilers, a greater (by 18.4%) relative weight (RW) of the abdominal fat compared with those consuming a deficient VitE diet was indicated [23]. The same birds showed higher spleen relative weights (RW; by 20%) and a greater relative length (RLE) of the duodenum (by 7.4%) and ceca (by 10.4%), compared with those consuming a VitE (200 mg/kg)-enriched diet [23]. A reduction in heart and liver RW (by an average of 31.3 and 3.5%, respectively) in broilers supplemented with a low amount of grape polyphenols in combination with VitE (25 mg/kg of GPP + 75 mg/kg of VitE) compared with broilers supplemented with VitE (100 mg/kg) only was observed [24]. In a more recent study, grape pomace supplementation (from 5% to 10%) did not affect broilers' relative organ and carcass weights, nor did supplementation with VitE (200 mg/kg) [25]. From the above studies, it appears that dietary PFA, in comparison to both a basal or a VitE-supplemented diet, can exert variable effects on carcass yield and quality and the weight of internal organs depending on the nature of the product tested, the dose employed, and the presence of stressors possibly affecting animal performance. 1.2 Meat Quality Characteristics (pH at 24 h Postmortem, Color, Shear Force Value, Cooking Loss, Intramuscular Fat, Sensory Qualities, Fatty Acid Composition)  
Meat quality characteristics are of great importance from a consumer perspective. In many papers, they have been evaluated alongside other variables, such as slaughter traits and the intrinsic characteristics of meat. The addition of different PFA at differing dietary inclusion levels did not affect meat color in poultry [12; 15; 23]. Moreover, PFA did not affect meat pH at 24 h post-mortem (pH24) in broilers and ducks [16]. The administration of sweet chestnut wood extract (SCW) to a basal diet did not modify pH, drip loss, and electrical conductivity of broiler meat [26]. Dietary supplementation with hesperidin (HE; at 0.3% of the diet) increased the pH24 compared with the basal diet, without differences from the VitE (200 mg/kg of the diet)-fed animals [13]. The dry matter, ether extract, and saturated fatty acid (SFA) content in HS broiler breast meat was not affected by the dietary inclusion of PP alone or in combination with VitE (PPE) compared with unsupplemented or VitE-supplemented animals or with those without heat stress [20]. Yellowness (b*) in the pectoralis major (PM) and ileotibialis (IL) muscles was improved in broilers consuming oregano plant (OP) compared with basal (by 41.4 and 56.7%, respectively) and VitE (by 51.9 and 74.1%, respectively)-enriched diets for 42 days [27]. Similarly, skin b* increased in nettle-supplemented diets compared with basal (by 90.7%) and VitE (by 77.6%) diets [22]. Lightness (L*) was also improved by 4.5% when broilers were fed with HE (0.15% of the diet) compared to VitE diets [13]. Broilers supplemented with RO (at 0.01, 0.015, 0.02% and VitE at 200 mg/kg of the diet) showed a greater pH24 in breast (by 1.2% on average) and thigh (on average, 0.68%) meat compared with RL-fed ones [18]. Muscle from broilers reared under HS had a greater ash content in the polyphenol- and VitE (200 mg/kg)-supplemented groups than in the negative (no HS and no supplementation) and VitE (100 mg/kg) control groups [20]. Moreover, PP-fed animals had a greater ash content than the positive (by 5.7%) and negative (by 9.8%) control ones.