Effects of Allicin on the Immune Performance and Expression of Immune-related Genes in Muchuan Black-bone Chickens

Background: In response to China’s ban on medicinal feed additives with growth-promoting functions in livestock and poultry feed, there is an urgent need in modern animal husbandry for alternatives to antibiotics to sustain livestock health and improve feed conversion efficiency. Allicin, known for its safety, efficiency, lack of drug resistance and absence of residue, regulates the intestinal flora structure; inhibits the growth of harmful bacteria; improves intestinal health, immunity and stress resistance; and improves animal production. Methods: To investigate the impact of allicin on immune performance and immune-related gene expression in Muchuan black-bone chickens, diets were supplemented with varying allicin levels (50, 100, 200 mg/kg), designated as test groups A, B and C, respectively. Initially, growth performance was assessed. Subsequently, immunoglobulins were measured via enzyme-linked immunosorbent assay (ELISA) and colorimetry; immune titers for avian influenza and Newcastle disease were evaluated using hemagglutination and hemagglutination inhibition tests and the expression of immune genes was analyzed via real-time quantitative PCR. Finally, serum biochemical indices in each group were determined. Result: Compared to the control group, allicin supplementation resulted in increased average fasting body weight in the experimental group and significantly (P less than 0.05) higher thymus and musogastric indices in groups A and C, respectively. Serum levels of immunoglobulin M in groups A and B and immunoglobulin G levels were significantly higher in all experimental groups than in controls. Antibody titers against avian influenza H5 and H7 strains were higher in all test groups, with Newcastle disease antibody titers in groups B and C significantly higher than those in controls. The mRNA expression levels of IFN-ã were lower across all experimental groups, whereas the expression levels of TLR3 in groups B and C and TLR15 in group B were higher. Serum levels of triglycerides in group A were significantly higher and blood urea nitrogen levels were significantly lower in groups B and C than in controls. These findings indicate that dietary allicin (50-200 mg/kg) significantly improves growth performance, immunity and protein and lipid metabolism in Muchuan black-bone chickens, offering valuable data for the development and use of allicin as an antibiotic alternative.