Comparative Analysis of Indoor and Outdoor Rearing Systems on the Meat Quality and Muscle Chemical Composition of Duroc Pigs

This study investigated the effects of an outdoor rearing system on the carcass characteristics, physical meat quality, and detailed muscle biochemical composition (amino acids, fatty acids, and minerals) of Duroc pigs. Twenty-four 3-month-old Duroc pigs with similar body weight were randomly assigned to either a conventional indoor (IN, n = 12) or outdoor (OUT, n = 12) rearing system for 45 days and fed the same commercial diet. No statistically significant differences were detected in primary carcass traits or muscle amino acid profiles between rearing systems (p > 0.05). However, OUT pigs showed significantly higher meat redness (a*, 6.42 vs. 5.65, p = 0.04) and cooking loss (25.21% vs. 22.05%, p = 0.049), along with reduced intramuscular fat (IMF, 4.17% vs. 6.30%, p = 0.048) and muscle sodium (Na, 0.040% vs. 0.045%, p < 0.001) contents. Furthermore, outdoor rearing profoundly restructured the muscle fatty acid profile, significantly increasing polyunsaturated fatty acids (PUFAs, including linoleic and linolenic acids) while decreasing total monounsaturated fatty acids (MUFAs). Pearson correlation analysis revealed that cooking loss was significantly correlated with Na content (p < 0.01), whereas the IMF percentage correlated with MUFAs, PUFAs, and the n6/n3 ratio (p < 0.05). In conclusion, outdoor rearing did not significantly alter primary carcass yields but promoted a leaner, more unsaturated nutritional lipid profile and a redder meat appearance.