Effect of Feeding Penicillin on the Life Cycle of the Chick ∗

Abstract

Summary

1. The feeding of penicillin stimulated the growth of birds fed an all-vegetable-protein diet. 2. Injection of the antibiotic into the birds fed the basal diet stopped the mortality and appeared to stimulate the growth. 3. Eggs were obtained from all groups. Pullets fed penicillin and injected with vit. B₁₂ had the highest egg production. Hatchability of eggs from birds injected with B₁₂ was within the normal range. No live chicks were obtained from pullets injected with penicillin from the 14th week. A 39%percnt; hatch was obtained from the eggs of pullets fed penicillin continuously. The B₁₂ content of the liver and kidney tissues and of the egg yolks was directly related to the injection of the vitamin into the birds. 4. Feeding of penicillin caused a significant increase in the total number of intestinal micro-organisms as indicated by thioglycollate counts. Penicillin likewise caused a significnat increase in the number of enterococci of the intestine during the first 14 weeks of the experiment. The administration of penicillin either orally or intravenously resulted in a marked increase in the number of penicillin resistant micro-organisms in the intestinal tract.