Alleviating heat stress-induced immune organ damage in ducks: Role of melittin.

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Heat stress, one of the major challenges facing the global livestock industry, can adversely affect the immune system. The present study explored the mechanisms by which melittin alleviates heat stress-induced immune organ damage. Three hundred 20-day-old male Huainan sheldrakes were randomly assigned to four groups: heat stress group (basal diet), heat stress + melittin group (I, II, III group, basal diet + 0.08, 0.12, 0.16g/kg melittin, respectively). The ducks were subjected to heat stress for 4h per day (temperature 36-38°C, relative humidity 60-70%) for 15 consecutive days. The results showed that compared with the heat-stress group, melittin improved the production performance of heat-stressed ducks, significantly increased serum immune indices (immunoglobulin G and interferon-gamma) and antioxidant indices (total antioxidant capacity, superoxide dismutase (SOD), and glutathione) (P < 0.05), and significantly decreased malondialdehyde (MDA) levels (P < 0.05). Additionally, melittin increased antioxidant function (nuclear factor-erythroid 2 p45-related factor 2, glutathione peroxidase, SOD, and catalase), and immune index (interleukin-10). Meanwhile, melittin significantly reduced immune indices (inducible nitric oxide synthase and cyclooxygenase-2), heat shock protein 70 expression, and apoptosis levels (P < 0.05) in heat-stressed ducks. Consequently, supplementing heat-stressed ducks with 0.12g/kg melittin increases serum immune function and antioxidants, alleviate heat stress-induced immune organ damage, and improve growth performance.