Functional role of Dictyota dichotoma extract in mitigating heat stress adverse effects and enhancing physiological resilience in growing rabbits
摘要
Elevating ambient temperatures driven by climate change are increasingly confronting animal productivity and health, particularly in heat-sensitive species like rabbits. Therefore, nutritional interventions are gaining attention for their role in enhancing heat tolerance. Brown seaweed Dictyota dichotoma (DD) extract is a rich source of bioactive compounds with potential health-promoting effects. Thus, this study assessed the protective influence of DD extract supplementation against natural heat stress in growing rabbits. A total of 120 rabbits were randomly assigned to four dietary treatments: a control diet (0 mg DD/kg) or diets enriched with 100, 200, or 400 mg DD extract /kg. The results showed that supplementation with DD extract significantly improved growth indicators. This improvement was seen in final body weight (P < 0.05) and feed intake (P < 0.001) in a quadratic effect, with the 400 mg/kg group showing the greatest gain (P < 0.001). Meanwhile, carcass quality and hematological parameters were significantly improved in a linear manner across all DD-supplemented groups (P < 0.001). The blood biochemical profiles showed decreased levels of creatinine, urea, ALT, AST, GGT, LDH, and sodium, indicating improved organ function (P < 0.05). The levels of thyroid hormones (T3 and T4) showed a quadratic increase, especially in the 200 mg/kg group (P < 0.001). Immune function was stimulated, as evidenced by increases in IgG, nitric oxide, lysozyme, and C3 concentrations (P < 0.001), while antioxidant capacity also improved through enhanced catalase, GPx, and TAC activities in a linear manner (P < 0.001). Concurrently, markers of oxidative stress (MDA, protein carbonyls, and 8-OHdG) were significantly reduced (P < 0.01). Moreover, acute-phase proteins such as Amyloid A and Haptoglobin were decreased (P < 0.001), while IL-10 levels rose (P < 0.001), supporting the extract’s anti-inflammatory potential. Finally, histological and immunohistochemical analyses confirmed that DD extract reduced tissue damage via regulating the HSP70 and MMP9 singling. In summary, dietary DD extract supplementation at a dose of 200–400 mg/kg effectively alleviated heat-induced physiological and immunological disruptions. This makes it a promising natural additive to enhance resilience and performance in heat-challenged rabbits.