Meat quality of a slow-growing chicken breed fed soybean meal-free diets

The complete replacement of soybean meal with alternative plant-derived protein sources in poultry diets represents a promising strategy to improve the environmental sustainability of feed formulations. This study investigated the effects of a soybean meal-free diet on growth performance, meat quality, lipid composition, proteomic profile, and sensory traits in the Italian native slow-growing chicken breed Bianca di Saluzzo. Ninety-six males were reared under identical semi-extensive conditions and fed either a conventional soybean meal-based diet (C) or an experimental soybean meal-free formulation based on field bean, pea protein, sunflower meal, and maize gluten as the protein sources. Birds were slaughtered at 147 and 174 days of age. Growth performance, carcass yield, and proximate meat composition were not affected by diet or slaughter age, confirming that the soybean meal-free feed ensured adequate nutrient supply. The experimental diet significantly increased linoleic (C18:2n6) and α-linolenic (C18:3n3) acid concentrations and enhanced the total essential fatty acid index in both breast and thigh meat, while reducing lipid oxidation and thrombogenicity index values, indicating improved oxidative stability and nutritional quality. Proteomic analyses showed no diet- or age-dependent clustering, suggesting stable muscle proteome expression in the birds fed the alternative feed. Higher scores for overall odour, sweetness, umami, and pungency were attributed to the meat from birds fed a soybean meal-free diet, indicating a richer flavour profile of this meat. Altogether, the complete dietary exclusion of soybean meal did not impair production performance or the technological quality of the meat, while enhancing health-related lipid indices and sensory attributes. These results demonstrate that a mixture of alternative protein sources can sustain productive efficiency and meat quality in native poultry breeds, supporting the development of resilient and environmentally responsible feeding strategies aligned with agroecological principles.