Dietary aqueous plant extract supplementation of pigs confers higher oxidative stability to meat.

Lipid oxidation negatively impacts the healthfulness of meat as it causes the formation of toxic compounds like malondialdehyde and cholesterol oxidation products, which have been demonstrated to negatively affect human’s health 1. For this reason, the meat industry extensively used synthetic antioxidants, especially in the past. However, in the last decade consumer’s opinion towards this kind of additives has become more and more negative due to safety issues. This forced the meat industries to take into consideration and test antioxidants of natural origin, by direct supplying in animal’s diets 2,3 or by direct addition into the final products 4-6. Plant phenols exhibit in vitro antioxidant activity, inhibiting lipid peroxidation by acting as chain-breaking peroxyl-radical scavengers 7,8. Therefore, they can play a protective role for highly unsaturated lipids in feed against oxidative damage 8, partly substituting the use of ?-tocopheryl acetate or synthetic preservatives. In this context, the impact of feeding a supplementation of oregano (Origanum vulgare L.) and/or rosemary (Rosmarinus officinalis L.) water extracts (Phenbiox; Calderara di Reno, Bologna, Italy) on the oxidative status of the pork meat was evaluated. The experimental protocol involved sixty-four Duroc x Large White pigs (45.8 2.3 kg at the beginning of the trial life weight, LW) that were divided into four groups (sixteen animals/group), each composed of eight barrows and eight gilts. Dietary group were: Standard diet, (CTR); Standard diet + 0.2% oregano (Origanum vulgare L.) aqueous extract (O); Standard diet + 0.2% rosemary (Rosmarinus officinalis L.) aqueous extract (R); Standard diet + 0.1% oregano aqueous extract + 0.1% rosemary aqueous extract (OR). All pigs were fed using a three-period feeding programme, which consisted of early grower (from the initial LW to 90 kg LW), late grower (from 90 to 120 kg LW) and finisher (from 120 to 180 kg LW, the typical slaughter weight of Italian heavy pigs) stages. During finishing, the different animal groups received a degermed corn-barley-soybean-based diet supplemented with 0.5% commercial source of conjugated linoleic acid (CLA; LodeStarTM CLA, Berg+Schmidt GmbH & Co., Hamburg, Germany), which included c9 t11 and t10 c12 isomers in equal parts. The animals were regularly slaughtered in a local slaughterhouse (final weight 185.0 14.8 kg). This study was conducted in accordance with the European recommendations for the protection of animals used for scientific purposes (EU Directive 2010/63/EU, September 22, 2010). At the slaughter, meat samples were obtained by cutting a tissue cube (1 cm × side) from one slice (1.5 cm thick) of the Longissimus lumborum muscle (LL) of 3 carcasses/group. These samples were lyophilized and then frozen at -20°C until analyses. Before analyses, the cubes were thawed (on ice), transferred to a Petri dish - on ice - and minced into smaller pieces with a surgical scissor. 100 g of each sample was homogenized (by Potter-Elvehjem tissue tissue grinder) in 3 mL of cold assay buffer containing Hepes 10 mM NaOH pH 7.4, 1.7 mg PMSF, 8.56 g of saccarose and 37.2 mg of EDTA and then centrifuged to remove the insoluble material. The supernatants were used to measure the Glutathione peroxidase enzymatic activity (GSHPx) 9. Protein concentrations of tissue lysates were determined by the Bradford protein assay 10 to express the GSHPx activity as U/mg of protein 9. A modified method of Folin-Ciocalteu was used for determination of the total amount of phenolics 11. Dietary supplementation of oregano and oregano plus rosemary significantly increased the GSHPx activity (275.4 and 242.4 U/mg of protein vs 101.7 and 154.5 U/mg of protein, respectively. P<0.001). The phenolic content was significantly higher in OR and R fed animals vs CTR and O (4.1 and 3.2 mg Acid Gallic Eq/g meat vs 2.5 and 2.8 mg Acid Gallic Eq/g meat, respectively. P<0.005). This study showed that the phytogenic antioxidants of oregano, alone or in combination with those from rosemary, were able to ameliorate the antioxidant status of pork meat with possible counteracting effects against meat lipid oxidation.