Abstract
Rabbits regulate their body temperature through their long ears and heart rate, but continuous heat stress negatively affects their reproduction, feed intake, body weight gain, immune response, and intestinal integrity. Recently, multiple herbal feed additives including volatile oils extracts were used in rabbits rations to mitigate hazards of heat stress. Nano-particles are substances have potential effects than their precursors, so this work aimed to investigate the potential role of Nano Nigella Sativa oils (NNS) against heat stress in rabbits. Seventy five New-Zealand rabbits with age of 35 days were allocated into five groups (15 rabbits per group subdivided into 3 replicate), group 1 was nourished a control diet without any additives, while group 2, 3, 4, and 5 were nourished a control diet plus NNS of 50, 100, 200, and 300 mg per kg of feed, respectively. All groups exposed for heat stress by elevating environmental temperature to 31 ºc for 5 hours per day along 42 days of experiment, at the end, feed intake (FI), live body weight (LBW), and body weight gain (BWG) were recorded, then Feed conversion ratio (FCR) were computed, as well as 3 rabbits from each group were sacrificed then blood samples were taken to measure immune response, and oxidative indices, in addition to collection of cecal contents for microbial count, and cecal tissues for MUC-2 gene expression. All treatments were alleviated the hazards from growing rabbits exposed for excessive heat and recorded an improvement of BWG, FCR, interleukin-6 (IL-6), MalonDiAldehyde (MDA), SuperOxide Dismutase (SOD), Glutathione Peroxidase (GPx), interleukin-10 (IL-10), microbial count, and MUC-2 but both treatments of 200 and 300 mg NNS have the highest significant beneficial role with non-significant effect between them. Therefore, 200 mg NNS was economically preferred as a feed additive choice in heat stressed growing rabbits.

Key words: Heat stress, rabbits, nanoparticles nigella sativa, immunity, oxidation, gut health