Astaxanthin Supplementation Mitigates Chronic Heat Stress-Induced Dysregulation of Glycerophospholipids and Sphingolipids in Broiler Thigh Muscle: Untargeted LC-MS Lipidomics Evidence

Chronic heat stress induces oxidative damage and lipid metabolic disruption in broiler skeletal muscle, yet its molecular effects on glycerophospholipids and sphingolipids remain poorly characterised. This study investigated the lipidomic effects of chronic heat stress and dietary astaxanthin (AST) supplementation (40 mg/kg) on broiler thigh muscle using untargeted liquid chromatography–mass spectrometry. Three experimental groups were established in this study, including a thermoneutral control group (Group A), a chronic HS group (Group B; 34 °C, 8 h/day), and an HS group supplemented with dietary AST (Group D). Orthogonal partial least squares discriminant analysis (OPLS-DA) revealed robust group discrimination (R²Y ≥ 0.987, Q²Y ≥ 0.784), with 301 differentially expressed lipid species identified (VIP ≥ 1 and P < 0.05.). HS significantly depleted polyunsaturated phosphatidylethanolamine species such as PE(54:3), PE(58:5), LPE(18:2), and LPE(22:5) and markedly reduced PI(42:0), indicating oxidative membrane phospholipid degradation. Concurrently, sphingolipid dysregulation was evidenced by pronounced accumulation of Hex1Cer(d18:2_22:5), sphingoid bases SPH(d15:1) and SPH(d16:1), and GM3 gangliosides, reflecting pro-inflammatory ceramide signalling. AST supplementation effectively reversed these disturbances, restoring glycerophospholipid abundance, suppressing ceramide accumulation, and normalising sphingoid base levels. KEGG pathway enrichment identified glycerophospholipid metabolism as the primary disrupted pathway. These findings demonstrate that AST serves as a potent nutritional intervention to stabilize the thigh muscle lipidome of broilers under chronic heat stress, offering new insights into maintaining muscle lipid quality in thermally challenged poultry farming.