Abstract
The study aimed to assess the mitigation of negative impacts of heat stress (HS) by the willow bark (Salix mucronata Thunb.) powder (SWBP) or betaine (BET) as natural antioxidants on semen quality, blood biochemicals, and oxidative status in rabbit bucks. Under control conditions, forty mature NZW adult males were distributed into five groups of eight replicates. The 1st group fed the basal diet without any additives (control), whereas the other groups were fed the basal diet contained 10 g of SWBP (SWBP(10)), 20 g of SWBP (SWBP(20)), 1 g of BET (BET(1)), or 2 g of BET (BET(2)) per Kg of diet. The results demonstrated that supplementing SWBP significantly reduced (P < 0.001) the respiration rates (RR), as well of ear (ET) and rectal temperatures (RT), while BET(2) recorded the lowest (P = 0.004) skin temperature (ST). All supplements markedly improved serum total protein, total lipid, and the activities of the AST and ALT (P < 0.001). Moreover, SWBP(20) and BET(2) enhanced serum albumin and globulin levels (P ≤ 0.01), superoxide dismutase, and total antioxidant capacity (P < 0.001). Both SWBP and BET also elevated testosterone levels and shortened reaction time (P < 0.001). SWBP(20) showed the highest testosterone and shortest reaction time. Semen quality parameters including pH, ejaculate volume, motility, sperm concentration, and viability were significantly improved (P < 0.05). In seminal plasms, both supplements increased glutathione and TAC levels while decreasing malondialdehyde (P < 0.001). The findings indicate that dietary SWBP and BET could improve semen quality, blood parameters, and oxidative capacity of rabbit bucks under HS conditions. Therefore, SWBP(20) or BET(2) could be used as HS alleviators for New Zealand White bucks during the hot Egyptian summer months by regulating the antioxidant/oxidative pathways to support reproductive health.