Effect of outdoor enrichment and dietary supplementation with n-3 fatty acid precursors and antioxidants on meat quality of free-range chickens

Growing consumer interest in animal welfare and product quality is increasing demand for products from less intensive farming systems. In poultry, dietary strategies such as supplementation with n-3 fatty acid precursors can enhance meat nutritional value. In outdoor systems, enriched pastures (e.g., grass and trees) promote locomotor activity and grass intake, facilitating the transfer of bioactive compounds into the meat. However, increased activity and higher n-3 PUFA levels may enhance oxidative processes, potentially affecting meat quality, particularly in thigh muscles, which are lipid-rich and highly involved in movement. The aim of this study was to assess the combined effects of outdoor enrichments and dietary supplementation with n-3 PUFA and antioxidants on the quality attributes and oxidative stability of thigh meat from free-range reared chickens. Four commercial chicken farms using males of a slower-growing genotype were considered in the study: two farms showing the outdoor area without pasture (NP), and two with the outdoor area enriched with grass and trees (GT). On each farm, two pens (20,000 birds each) were assigned to either a control (C) or a supplemented diet (S; 5% linseed, vitamin E and selenium). Birds were slaughtered at 56 d of age. Thigh samples were collected to assess the main meat quality traits (i.e., pHu and colour) (n=120; 15/group) and oxidative status (TBARS and carbonyl content; n=64; 8/group) after 0, 3, and 7 d of refrigerated storage (4°C). Data were analyzed by two-way ANOVA, including the outdoor enrichment and the diet, as well as their interaction in the model. The differences observed on fresh meat (0 d of storage) indicated that the outdoor enrichment have played a more prominent effect than the dietary treatment on meat characteristics. In particular, higher pHu as well as lower lightness were observed in GT samples compared to NP (6.11 vs. 5.92; p<0.001 and 53.6 vs. 54.8; p<0.001, respectively). During refrigerated storage, oxidative processes affected both the lipid and the protein fractions, regardless of pasture type and diet. In detail, the highest TBARS values observed in the GT-S group at d 0 (1.70 mg MDA/kg meat; p<0.05) may be attributed to the combined effect of increased locomotor activity in the birds belonging to this group that, concurrently, had higher n-3 PUFA levels in the meat (data not shown). In fact, long-chain n-3 PUFA are very susceptible to peroxidation due to their chemical structure. In the present study, GT-C group showed the highest level of carbonyls at 3 d of storage (6.69 nmol/mg of protein; p<0.05). This can be mainly ascribed to the high locomotor activity of birds fed the C diet, which did not receive antioxidants supplementation. In fact, it is likely that the antioxidant content of the C diet was not sufficient to mitigate the oxidation process triggered by the increased movement. In conclusion, dietary enrichment with n-3 PUFA and antioxidants can differently affect chicken meat quality depending on the presence of grass and trees, which may enhance animal movement and promote muscle oxidative processes. This study is part of the INTAQT Horizon 2020 project, which aims to establish a link between husbandry systems and the intrinsic quality of animal products.