Influence of Environment on the Growth Response of Chicks to Penicillin

COATES et al. (1951, 1952) reported that chicks reared from day-old to 3 weeks of age in quarters not previously used for chick experiments failed to show a growth response to penicillin. Chicks raised in such quarters, regardless of the presence of antibiotic in the diet grew as well as chicks receiving antibiotic in long established quarters. These workers suggested that an infection was present in the latter birds, which, while not grossly evident, nevertheless was responding to penicillin, with a resultant improvement in the growth of the birds. Bird et al. (1952) found support for the observations of Coates et al. They showed that a response to aureomycin was evident after one week in long used quarters but not until three or four weeks in new quarters. Birds four weeks of age moved from the new quarters to the long used quarters and deprived of antibiotic, experienced a marked …