Abstract
Background: Coccidiosis, caused by protozoa of the genus Eimeria, remains one of the most economically important poultry diseases. Beta glucans, naturally occurring polysaccharides derived from yeast, possess potent immunomodulatory properties and have been shown to enhance innate and adaptive immune responses. The present study investigated the effects of β-1,3/1,6-glucan (Polymune®), produced from a novel strain of Aureobasidium pullulans, on growth performance, immune function, and intestinal health in broiler chicks vaccinated against coccidiosis. Methods: A total of 108 day old Cobb 500® broiler chicks were assigned to a 2 × 3 factorial design with β-glucan supplementation at 0%, 0.1%, or 0.3% via drinking water from days 1–14, with vaccinated groups receiving an 18× dose of a live attenuated Eimeria vaccine
(EVANT®) on day 7. Performance indicators included body weight gain (BWG), feed conversion ratio (FCR), gut morphometry, oocyst per gram (OPG) counts, qPCR of Eimeria spp. and heterophil-to-lymphocyte (H/L) ratio. Ileum and liver histological lesions were scored using the “I See Inside” (ISI) methodology. Results: On day 14,
significant differences in BWG were observed due to vaccination (P = 0.002), with no interaction between vaccination and β-glucan supplementation. Vaccination significantly
increased relative liver weight (P=0.010), while β glucan supplementation had no effect (P > 0.05). OPG counts were significantly elevated in all vaccinated groups (P < 0.0001), peaking on day 12, while unvaccinated groups remained negative. β glucan dosage did not significantly influence OPG counts (P=0.7771); however, high-dose supplementation (0.3%) showed a numerical reduction in OPG among vaccinated birds. Birds supplemented with 0.3% β-glucan without vaccination showed higher ISI scores in ileum
(17.0 ± 3) and liver (16.0 ± 3) which is comparable to the vaccinated groups. Conclusion: Overall, β 1,3/1,6-glucan showed mixed effects on immune and gut health parameters, with higher doses potentially contributing to enhanced immune response.

Keywords Beta glucan, Eimeria, Live Coccidiosis Vaccine, Broilers