Antibiotics in Mature Fowl Nutrition.

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Abstract
Hatch-ability of eggs from birds fed an unsupplemented diet decreased to zero after the 4th wk. Injn. of vit. Bl2 into the hens improved hatchability somewhat. The feeding of aureomycin and penicillin alone apparently assisted in depleting the birds of vit. B12 and possibly of the unidentified factor. Liver "L" contained a factor necessary for normal hatchability and embryonic development. The B12 content of the egg yolks was detd. by a standard microbiological assay. Injn. of vit. Bl2 and the feeding of an APF concentrate and Liver "L" produced egg yolks that contained approx. the same amts. of vit. Bl2. Hatchability of eggs from hens fed the practical all-mash diet was about 90% during the test period, but the vit. B12 content of egg yolks from these birds was lower than that from others injected with vit. B12 or fed B12 in the form of an APF concentrate or Liver "L".