Comparative immune response of four chicken genotypes to newcastle vaccine and TLR4 gene polymorphisms

Indigenous chickens are known to be more resistant to a wide range of diseases compared to their exotic counterpart. This research seeks to evaluate the response of four chicken genotypes to the Newcastle vaccine and determine the genetic variations across the four genotypes based on the TLR4 gene. A total of 120 day-old chicks comprising 78 normal feathers, 20 exotic genotypes, 16 frizzle feathers and 6 naked necks, obtained from Abeokuta and Ibadan in Nigeria were used for this study. After two weeks of acclimatization, all the birds were vaccinated against Newcastle disease with the Lasota strain. Blood samples for antibody titre were obtained 14 days post-vaccination. Polymerase chain reaction amplification was carried out at IITA Ibadan. Results for the antibody titre revealed that frizzle feather had a significantly higher antibody titre with 0.923±0.01 and 0.903±0.00 for the first and second antibody titre, respectively. Similarly, the highest polymorphism, with 36 polymorphic sites, and the highest haplotype numbers (10) were observed in Frizzle and Normal feathers, while the lowest polymorphism was found in the exotic breed (15), and the highest nucleotide diversity (0.114±0.0545) was also noted in Frizzle feathers. We presumed that the indigenous breed may be more reactive to the Newcastle vaccine regarding antibody titre than the exotic breed (broilers). Correspondingly, the genetic polymorphism and genetic distance studies further suggest that the variations observed in the antibody titre may be associated with their genetic makeup. Hence, the frizzle feather may be more resistant to Newcastle disease and has more variations than the other genotypes studied.