Background and Aim: Steviol glycosides extracted from the leaves of Stevia rebaudiana Bertoni have been of much consideration recently because of their beneficial effects on health, raising the possibilities for improving farm animals' health. Although some studies on stevia's dietary effect on body weight gain are available, few studies have been conducted to evaluate stevioside supplementation on immune response in broilers. This experiment aimed to analyze how a stevia-based sweetener can affect broiler chickens' growth performance and humoral response.

Materials and Methods: In this experiment, one hundred and twenty 1-day-old Cobb-line broiler chicks fed with commercial starter/grower diets were included in three groups and supplemented with stevia-based sweetener at levels 0, 80, and 160 ppm, respectively. Chickens were weighed on day 0 and every 7 days for the next 6 weeks. Chicks were then immunized on days 10 and 24 with a Newcastle and infectious bronchitis vaccine and blood sampled on days 7, 24, and 35. Serologic assays were performed to detect specific antibody levels.

Results: The body weight means and body weight gain on day 42 were found to be significantly higher in birds from the group fed with 80 ppm of stevia-based sweetener than those in the control group and slightly higher than those in the group supplemented with 160 ppm of stevia-based sweetener. Likewise, on day 35, antibodies against the Newcastle disease virus were higher in the treatment groups. Immune response to infectious bronchitis virus vaccination was not statistically different among the three groups through the experiment.

Conclusion: Stevia-based sweetener at 80 ppm in commercial-based diets improved body weight gain and immune response in broiler chickens at the market age.

Keywords: body weight, broilers, immune response, stevia, sweetener.