Abstract
The effect of feeding procaine penicillin G (50mg/kg diet) from birth on the electrophoretic pattern of the serum of young conventional chickens was studied and compared with data obtained from germfree animals. The effect on the morphological characteristics of the conventional chickens, e.g. the reduction in weight of the cecal lymph nodes is known to make itself felt at an age of one month or earlier. In the electrophoretic pattern, no differences were seen up to the age 2.5 months. Both treated and non-treated conventional animals showed an equal increase in gamma globulin with age. At the age of four months, however, the antibiotic treated birds showed lower gamma globulin values than the untreated group, though the level was still substantially higher than found in the germfree serum. The germfree chickens showed a much lower level from the start which did not increase appreciably with age.