Dietary Effects on Development of Pancreatic Xanthine Dehydrogenase in the Newly Hatched Chick

Abstract
Chick pancreatic xanthine dehydrogenase (PXDH) is synthesized in response to feeding after hatching; its specific activity increases more than 200-fold within a week. Unfed chicks develop little PXDH activity. To determine which dietary ingredients were critical in regulating this developmental pattern, chicks were fed synthetic diets in which each ingredient was varied independently. Except for those containing unsaturated fatty acids or excess arginine, each diet supported PXDH activity and weight gain to the same extent, indicating that growth and PXDH synthesis are regulated together. No dietary ingredient was found which would enhance PXDH activity above the level predicted by weight gain. Three ingredients suppressed PXDH activity: linoleic and linolenic acids and arginine. These are found in high concentrations in egg yolk. At hatching, the chick's nutritional intake normally shifts from yolk to a predominantly grain diet containing lower concentrations of these acids; this change is probably important in the initiation of PXDH accumulation.