Immunocompetence Status of White Plumage Naked Neck versus Normally Feathered Broilers in Tropical Climate

The study was undertaken to evaluate the effect of naked neck gene on mortality, cell mediated and humoral immune response in white plumage broiler population. The mortality of homozygous naked neck (Na/Na) broilers (11.71%) was comparatively lower than that of heterozygous naked neck (Na/na) (12.28%) and normally feathered (na/na) (13.59%) broilers. The humoral immune response was measured against (1% v/v) sheep red blood cells (SRBC) for total haemagglutinin (HA) antibody, 2-mercaptoethanol resistance (MER) or (IgG) antibody and 2-mercaptoethanol sensitive (MES) or (IgM) antibody titre on 7 days post-immunization. The titre was expressed as log2 of the highest dilution which shows complete haemagglutination. Total HA titers of Na/Na and Na/na (11.05±0.53 and 11.09±0.38) were comparatively higher than that of na/na (10.26±0.42). The MES antibody titre of Na/Na (8.50±0.53) and Na/na (7.63±0.45) broilers were significantly higher as compared to na/na (6.11±0.32) broilers. The MER titre of na/na genetic group (4.15±0.42) was significantly higher than Na/Na (2.55±0.37) and comparatively higher than Na/na (3.45±0.38) broilers. In vivo cell response to phytohaemagglutinin-P (PHA-P), measured as Foot Index (FI) in mm expressed significantly higher response in Na/na (0.473±0.05) and Na/Na (0.413±0.04) broilers as compared to na/na (0.304±0.03) broilers. The result of present study suggested that white plumage naked neck broilers had better immune response as compared to normally feathered broilers. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 4 : 560-563)