Document Type : Research Paper
Authors
1 Department of Animal Sciences, Cha.C., Islamic Azad University, Chalus, Iran.
2 Department of Animal Sciences, Cha.C., Islamic Azad University, Chalus, Iran
Abstract
Objective: The Stock density is one of the most important management factors in the poultry industry, directly affecting the health, performance, and welfare of broiler chickens. However, high stocking density can exert various negative effects on birds ‘physiological status and performance, particularly during the later stages of growth. To alleviate the adverse impacts of high stocking density, the use of natural and safe feed additives such as herbal extracts and organic acids has been proposed as an alternative to antibiotic growth promoters in poultry nutrition. The present study was conducted to evaluate the effects of dietary encapsulated acidifier and herbal extracts administered via drinking water on growth performance, carcass characteristics, jejunal morphology, ileal microbial population, and immune response of broiler chickens under different stocking densities.
Methods: A total of 630 one-day-old male and female Ross 308 broiler chicks, with an average initial body weight of 42.61 ± 0.58 g, were used. The experiment was arranged in a completely randomized design with a 3 × 3 factorial arrangement, consisting of nine treatments and five replicates per treatment. Stocking densities were set at 12, 14, and 16 birds per square meter. Experimental treatments were included three stocking densities (12, 14, and 16 birds/m²) and three additive types (control, encapsulated acidifier, and herbal extracts). Growth performance parameters, including feed intake, body weight gain, and feed conversion ratio, were recorded during the starter (1–10 d), grower (11–24 d), and finisher (25–42 d) periods. Carcass characteristics, jejunal morphology, ileal microbial population and relative antibody titers against infectious bronchitis (IB), infectious bursal disease (IBD), and newcastle disease virus (NDV) were measured at 42 days of age.
Results: The results indicated that both the acidifier and herbal extracts significantly mitigated the adverse effects of the greatest stocking density (16 birds/m²) on body weight and weight gain. Birds reared at 12 birds/m² showed a greater relative breast weight compared to those reared at 16 birds/m² (P<0.05). Increasing stocking density from 12 to 16 birds/m² decreased relative spleen weight (P<0.05). The use of acidifier and plant extract supplements in the diet of broiler chickens increased the villus height compared to diets without additives (P<0.05). The interaction effects of additive type and density level showed that the use of acidifier and plant extract supplements in the diet of broiler chickens raised at a density of 16 compared to a density of 16 without additives significantly increased the number of Lactobacillus and significantly decreased the number of Coliforms (P<0.05). A significant interaction between stocking density and additive type was observed, showing that supplementation with herbal extracts at both 12 and 16 birds/m² increased the antibody titer against IBD compared with un supplemented groups at the same densities (P<0.05). Moreover, broilers receiving herbal extract supplementation exhibited grater antibody titers against NDV than those fed diets with acidifier or without additives (P<0.05). Increasing stocking density from 12 or 14 to 16 birds/m² significantly reduced antibody titers against IB (P<0.05).
Conclusion: In conclusion, supplementation with encapsulated acidifier and herbal extracts improved growth performance, villus height, ileal microbial population, spleen weight, and antibody titers against NDV and IBD, suggesting their potential to alleviate the negative effects of high stocking density stress in broiler chickens.
Keywords
)