Breed and Age Differences in Serum Immunoglobulin (IgG) Level in Chickens

The immunoglobulin (IgG) levels of sera of White Leghorn (WL), White Cornish (WC), New Hampshire (NH) and White Plymouth Rock (WPR) laying hens were determined by the radial immunodiffusion technique of MANCINI et al (1965). Serum IgG levels for WL, WC, NH and WPR were 987.6, 913.6, 889.0 and 602.8mg per 100ml, respectively. Coefficient of variation of them was 30-40%. Serum IgG levels in WL and WPR were determined from 2 days of age to 40 weeks of age. At 2 days of age, serum IgG levels for WL and WPR were 530.1 and 316.1mg per 100ml, respectively. These levels decreased drastically until 2 weeks of age, and then increased until 15 weeks of age. They reached 1026.0 and 633.3mg per 100ml, at 15 weeks of age, respectively. Thereafter, those kept relatively constant. The serum IgG level of WL was significantly higher than that of WPR at 2 days and 4 weeks of age and thereafter. Correlation coefficient of serum IgG levels between 10 weeks and 15, 20 or 40 weeks of age for WPR was comparatively high. No sex difference in serum IgG level was observed.