Abstract
This study evaluated the effects of combined dietary supplementation with Nigella sativa seeds (NSS) and β-glucan (βG) on growth performance, intestinal histomorphology, oxidative status, immune responses to Newcastle disease (ND), avian influenza (AI), and infectious bursal disease (IBD), and protection against ND virus (NDV) challenge in broiler chickens. Ninety-six 1-day-old chicks were randomly allocated into three groups, with three replicates each: vaccinated control (G1), vaccinated and NSS/βG-supplemented (G2), and non-vaccinated, non-supplemented (G3). G3 was further divided into NDV-challenged positive controls (G3A) and negative controls (G3B). the G3 . All groups, except the negative controls, were challenged with NDV at 35 day of age (D). Dietary supplementation tended to enhance ND-, IBD-, and AI-specific antibody titers following vaccination. After NDV challenge, both vaccinated groups showed markedly reduced mortality compared with the positive control (40%), while G2 exhibited significantly lower oropharyngeal viral shedding than G1 (P<0.05). The thymus index significantly increased in G2 at 14, 21, 28, and 35 D. Compared with G2, G1 showed inferior growth performance, antioxidant capacity, erythrocyte indices, and leukocyte profiles at 21 D (P<0.05). These parameters were significantly improved in G2, accompanied by higher expression of insulin-like growth factor-1 (14.37-fold vs. 8.69-fold in G1). Enhanced innate immunity in G2 was indicated by increased phagocytic activity and index and a reduced heterophil-to-lymphocyte ratio. Intestinal histomorphology was compromised in G1 compared with G3, whereas G2 consistently exhibited the greatest villus height and crypt depth at both sampling ages (P<0.05). In conclusion, combined NSS and βG supplementation enhances vaccine efficacy, immune competence, growth performance, intestinal health, antioxidant status, and protection against NDV in broiler chickens.

Key words: growth performance, Newcastle disease, virus, chickens, vaccine, Nigella sativa, β-glucan, infection