Translocation of antibiotics in developing avian embryos.

Kanamycin, penicillin, and streptomycin were injected individually into air cells of newly set chicken and turkey hatching eggs, and assay was made throughout the incubation period to determine the location, potency, and duration of efficacy. By 24 hours, each antibiotic had diffused throughout the albumen. By six days, penicillin residues could not be detected, whereas kanamycin or streptomycin was found within certain areas of the developing embryo and in newly hatched chicks or poults. The migration patterns for kanamycin and streptomycin were markedly similar, and for turkeys the following results apply: antibiotic residues were detected in albumen (incubation days 1-22); yolk (day 13 to 6th day after hatching); amniotic fluid (days 16-23); and cloacal or cecal content (day 24 to 6th day after hatching). The findings indicate that the antibiotics did not diffuse into the yolk or amniotic fluid from the albumen but were translocated to those sites during normal embryonic development, and subsequent movement of drugs was not via the blood, since none was found in whole blood or serum (tested day 13 to 11th day after hatching). Antibiotic residues were not detected in allantoic fluid (tested days 6-24), and this could be a site of persisting pathogens in treated eggs. Evidence of drug levels in postembryonic yolk sac contents and intestines suggests that treatment of hatching eggs may offer some protection in newly hatched birds.