Effects of Dietary Levels of Bay Laurel Leaf Extract Conjugated With Zinc Nanoparticles on Growth Performance, Carcass Traits, and Blood Parameters in Broilers

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.