Impact of Naked neck (Na) and Frizzle (F) genes on general immunocompetence in egg type chicken

Tropical oriented major genes Naked neck (Na) and Frizzle (F) were introgressed in two populations of White Leghorn at Central Avian Research Institute, Izatnagar (India). Major genes are believed to confer not only adaptability to the tropical climate, but also resistance to diseases. Disease resistance is composed of three basic sub-systems, the humeral, cellular and phagocytic. The humeral response is evaluated through antibody response to SRBCs, in vivo cell mediated (CMI) response to PHA-P. Total HA titre, 2-mercaptoethanol resistance (MER) and 2-mercaptoethanol sensitive (MES) antibody titre were estimated on 5 day post injection (dpi). Mean titres (log₂) at 5 dpi for HA, MER and MES in Naked neck were 8.810±0279, 3.180±0.150, 5.630±0.269 and corresponding values for Frizzle were 8.429±0.279, 2.776±0.105, 5.653±0.269, respectively. There was no significant difference between varieties for the humoral immune response. CMI response to PHA-P was evaluated by injection of PHA-P into toe- web between second and third digit of chicks. The effective mean swelling measured after 24, 48 and 72h post PHA-P injection in Naked neck and Frizzle varieties were 0.339±0.032, 0.097±0.031, 0.072±0.024 and 0.136±0.014, 0.091±0.017, 0.069±0.012 mm, respectively. CMI to PHP-A differed significantly (P<0.05) between two varieties and among time. CMIR observed at 24h was statistically (P<0.05) higher in Naked neck than Frizzle.

It was concluded that when all four immunocompetence traits were considered together, Naked neck was adjudged better than Frizzle. Introduction of Naked neck and Frizzle genes may be taken into consideration for improving disease resistance, particularly in tropical environment.