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

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, 0.16 g/kg melittin, respectively). The ducks were subjected to heat stress for 4 h 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 0.12 g/kg melittin increases serum immune function and antioxidants, alleviate heat stress-induced immune organ damage, and improve growth performance.