* Corresponding author: email -skgcari@yahoo.co.uk.
1 Department of Animal Science, MJP Rohilkhand University, Bareilly
Immunocompetence (IC) traits viz., antibody response to SRBC, serum lysozyme and IgG concentration were studied in 484 chicks (330 and 154 from HSRBC and LSRBC lines) at the age of 5–6 weeks belonging to third generation of specialized white Leghorn chicken lines divergently selected for humoral response to sheep erythrocytes. Genetic and phenotypic parameters were estimated using half-sib correlation method separately for both the lines, taking hatch and sex as fixed effects in the model. Least squares means of HA titre, serum lysozyme and serum IgG were 8.06±0.22, 2.85±0.08/ml and 33.91±1.68 mg/ml in HSRBC and 7.87±0.26, 2.77±0.09/ml and 31.65±1.28 mg/ml in LSRBC lines. All the traits in both the lines were significantly affected by hatch. Significant (P<0.05) sexual dimorphism was observed in serum lysozyme levels in HSRBC line. Heritability estimates were low in HSRBC line and could not be estimated in LSRBC line, probably due to smaller sample size. Phenotypic correlations among IC traits in both lines were low (P>0.05). Divergent selection significantly influenced humoral response and serum IgG levels; HSRBC line demonstrated higher magnitudes. It may be inferred that selection for response to sheep erythrocytes alone or in combination with other facets of immunity may improve the host defense in layer chicken.
Genetics, immunocompetence trait, specialized WLH line
