Association of Natural Resistance-Associated Macrophage Protein 1 Gene With ND Antibody Titer and Leukogram...

Newcastle disease (ND) is a major infectious disease impacting chicken productivity. The natural resistance-associated macrophage protein (NRAMP1) gene plays a critical role in the innate immune response. This study aimed to evaluate the association between NRAMP1 gene polymorphisms, ND antibody titers, and leukogram parameters in three local Indonesian chickens: Kampung, Red Kedu, and their crossbreds. Each group consisted of 50 four-week-old chickens. Blood samples for ND antibody titers (via hemagglutination inhibition test) and total and differential leukocyte counts were collected 21 days postvaccination. DNA for genotyping was extracted at 8 weeks of age. Genotyping was conducted through sequencing. Data were analyzed using ANOVA, with post hoc comparisons by Duncan's multiple range test. Genetic parameters such as allele/genotype frequencies, heterozygosity, and genetic distances were also determined. Results revealed three genotypes at the NRAMP1 locus. The CC genotype predominated in Red Kedu (40%) and crossbred chickens (41.5%). A strong correlation was observed between the NRAMP1 genotype and ND antibody titer (r = 0.744, p < 0.01). Additionally, genotypes were significantly associated with leukogram parameters, namely, heterophils (r = -0.858), lymphocytes (r = 0.855), and H/L ratio (r = -0.862). Chickens with the TT genotype showed higher ND antibody titers, increased lymphocyte percentages, and lower H/L ratios, indicating better immune response and lower stress. Allele frequency analysis showed a slightly higher prevalence of the C allele (0.515) over T (0.485). The T allele had positive additive effects on ND antibody titers and lymphocyte percentages. Breeding value estimates suggested that the TT genotype possesses superior genetic potential for immune-related traits. High genetic variance for ND titers also highlighted significant biodiversity, underscoring the value of NRAMP1 polymorphism in breeding strategies for disease resistance. Therefore, this study suggests that the NRAMP1 gene has potential as a biomarker for ND resistance and could be considered for use in breeding programs of the Indonesian local chickens. The study recommended further studies to investigate chickens that are challenged with a virulent ND strain to validate findings from this research. Furthermore, future studies should consider sequencing the complete fragment of the NRAMP1 gene.