Growth performance, immune status and organ morphometry in broilers fed Bacillus subtilis-supplemented diet

The present research aimed to investigate the effects of Bacillus subtilis (B. subtilis) on performance, immune system, gut, and lymphoid organs’ microarchitecture in broilers. A total of 120 day-old broiler chicks were randomly distributed into four groups. The birds were fed a corn-soy-based basal diet (BD) (control) or the same BD supplemented with 10% zinc bacitracin (ZnB), 0.05 g/kg or 0.1 g/kg of B. subtilis (BS). The broilers fed 0.1 g/kg of B. subtilis had superior mean bodyweight and lower feed conversion ratio compared with the non-supplemented or ZnB-fed groups. The BS-0.1 group registered higher antibody titer against the Newcastle disease (ND) virus. Cell-mediated immune response post Phytohaemagglutinin-P (PHA-P) injection was attained by both BS-0.1 and BS-0.05 groups. Histomorphological study revealed increased thymus cortical width, and cortex/medulla ratio in BS-0.1 group compared with control. Area of bursal follicles and germinal centres of spleen also improved in BS-0.1 group. Compared to ZnB and control, higher villus height (VH) and villus crypt ratio of the duodenum and jejunum were recorded on day 21, and higher VH of duodenum and ileum was noted on day 35 in BS-0.1 and BS-0.05 groups. In conclusion, B. subtilis-type probiotics contributed positively to better growth performance, improved immune system and modulated morphology of lymphoid organs and gut mucosa in broilers.Keywords: Immunity, intestinal mucosa, poultry, probiotics