Antibiotics in Mature Fowl Nutrition. ∗

Abstract

Summary

Data have been obtained on the effect of feeding aureomycin, penicillin, streptomycin and APF concentrate and Liver “L” in a diet low in vit. B₁₂. Hatchability of eggs from birds fed this diet unsupplemented decreases to zero after the fourth week. Injection of vit. B₁₂ into the hens improved hatchability somewhat. The feeding of aureomycin and penicillin alone apparently assisted in the depletion of birds of vit. B₁₂ and possibly of the unidentified factor. Liver “L” contains a factor necessary for normal hatch-ability and embryonic development. The B₁₂ content of the egg yolks was determined by a standard microbiological assay. Injection of vit. B₁₂; feeding of an APF concentrate and the feeding of Liver “L” produced egg yolks that contained approximately the same amounts of vit. B₁₂. Hatchability of eggs from hens fed the practical all-mash diet was about 90% during the test period. Yet, the vit. B₁₂ content of egg yolks from these birds was lower than that of similar birds injected with vit. B₁₂ or fed a source of vit. B₁₂ in the form of an APF concentrate or Liver “L.”