Abstract
Summary
Feeding nicarbazin to laying hens resulted in less protoporphyrin on their egg shells. The decrease varied in proportion to dietary intake and a linear response was obtained between dietary levels of 0.002–0.010% nicarbazin. Tissue homogenates of follicular membranes, magnum. isthmus, uterus, and small intestines from laying hens catalysed the formation of porphyrins from ALA. Homogenates of isthmus and uterus were more potent than those of other tissues examined. Tissues from medicated hens formed as much porphyrin from ALA as those from nonmedicated hens. Erythrocyte-porphyrin formation induced by repeated bleeding was not inhibited in medicated hens which were laying eggs with shells containing 75% less porphyrin than controls. These data suggest that decreased deposition of shell protoporphyrin caused by feeding nicarbazin does not result from inhibition of porphyrin synthesis.
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