Abstract
This study aimed to evaluate the effects of bay laurel leaf extract conjugated with zinc nanoparticles (Zn-Nano-BLLE) as a growth enhancer and antibiotic alternative in broiler diets on growth performance, carcass characteristics, and blood markers. In a completely randomized design, 264 one-day-old Ross 308 broiler chicks were divided into four experimental groups to assess the impact of Zn-Nano-BLLE supplementation. Each group consisted of six replicates, each containing 11 unsexed chicks. The treatments were as follows: a control group (basal diet) without any additives, and three experimental groups receiving Zn-Nano-BLLE at 1, 2, and 3 cm³ Zn-Nano-BLLE/ kg feed, respectively. Results indicated that Zn-Nano-BLLE supplementation at 1 or 3 cm³/kg feed led to significant improvements in live body weight and weight gain. The lowest feed intake and feed conversion ratio were observed in broilers supplemented with 1 cm³ Zn-Nano-BLLE/kg feed (30.94 and 1.14, respectively). However, the highest dressing, carcass, and heart percentages were found in the control group. Additionally, broilers fed 3 cm³ Zn-Nano-BLLE/kg feed showed the highest levels of total protein, albumin, and globulin, while also exhibiting the lowest levels of total cholesterol and low-density lipoprotein (161.52 and 88.35, respectively). The immunoglobulin G (IgG) levels were elevated in the supplemented groups, although no significant effects were noted on immunoglobulin M (IgM). Birds given 2 cm³ Zn-Nano-BLLE/kg feed demonstrated the highest superoxide dismutase activity (164 U/ml), while the control group had the lowest levels. In conclusion, dietary inclusion of Zn-Nano-BLLE, particularly at 1 and 3 cm³/kg, enhanced broiler immunity, productivity, and antioxidant status, indicating its effectiveness as a natural growth enhancer in broiler production.