Background and Aim: Rhazya stricta is a herbal plant widely used in traditional medicine due to its proficiency and naturalness with few side effects. In this study, we investigated the impact of using an R. stricta extract supplement on broiler chickens' performance, especially the immune system.

Materials and Methods: In addition to the control group, one group received the methanol extract of R. stricta in drinking water for the first 2 weeks before being challenged with sheep erythrocytes (SRBCs), while the other group was challenged with SRBCs without receiving the R. stricta treatment. We evaluated cellular immunity by determining the phagocytic activity and lymphocyte (L) proliferation and assessed humoral immunity by quantification of the serum total IgM and IgG. We measured the serum levels of antioxidant enzymes and performed a histological examination of the spleen and the bursa of Fabricius (BF).

Results: Our results indicate a significant enhancement in cellular immunity in the group supplemented with R. stricta as demonstrated by a significant increase in the phagocytic activity, L proliferation, and percentages of circulating L (p<0.05). The chickens treated with R. stricta exhibit an enhanced humoral response shown by a significant elevation in the serum levels of the total antibodies of the IgM and IgG isotypes, along with a notable increase in BF activity. Furthermore, R. stricta supplementation is associated with a significant increase in the serum levels of catalase and superoxide dismutase (p<0.05), along with a significant improvement in broilers' general performance, body weight, and feed efficiency.

Conclusion: Our results suggest an immunomodulatory effect for the methanol extract of R. stricta and highlight the potential use of this plant in preventive and therapeutic medicine.

Keywords: antioxidants, chickens, immunomodulation, Rhazya stricta.