Effects of dietary supplementation with Laurus nobilis extract on growth performance, carcass features, blood lipid profile, immunity, antioxidative status, digestive enzymes, and gut microbial load in growing New Zealand white rabbits.

This study evaluated the effects of supplementing the diet of growing New Zealand White (NZW) rabbits with Laurus nobilis extract (LNE) on their growth, immune function, digestive enzyme activity, and cecal microbiota. One hundred 5-week-old male New Zealand White rabbits were randomly assigned to five treatment groups (n = 20 per group) in a completely randomized design. The control group received a basal diet, while the other four groups received the basal diet supplemented with LNE at 1, 2, 3, and 4 g/kg, respectively. Results shown that higher LNE supplementation (3-4 g/kg) significantly improved growth parameters, including live body weight (LBW), body weight gain (BWG), feed intake (FI), and feed conversion ratio (FCR). Notably, with 4 g/kg LNE supplementation, there was a marked improvement in carcass characteristics, with reduced abdominal fat (P < 0.043) and increased percentages of dressing, carcass (P < 0.0051), and spleen (P < 0.0198). Furthermore, higher doses of LNE were associated with a reduction in lipid profiles, including decreases in total cholesterol (TC, P < 0.0004), triglycerides (TG, P < .0001), low-density lipoprotein (LDL, P < .0001), and very LDL (VLDL, P < .0001). Immune responses such as immunoglobulins M (IgM), G (IgG), A (IgA), and lysozyme were significantly improved in all LNE groups (P < 0.001). Antioxidant indicators, including superoxide dismutase (SOD, P < 0.0005), total antioxidant capacity (TAC, P < 0.0007), and glutathione peroxidase (GPX, P < .0001), were also enhanced by LEN dietary inclusion. In terms of gut health, pathogenic bacteria such as E-coli, Salmonella spp Coliform and were declined in all LEN supplementation (P < 0.01). Additionally, digestive enzymes including amylase, lipase and protease activities were enhanced by feeding LNE (2, 3 and 4g/kg diet, P < .0001). These findings suggest that LNE supplementation, particularly at 4 g/kg, enhances the growth, health, and metabolic efficiency of NZW rabbits, providing potential benefits for their overall grwoth and well-being.