Effects of Increased Vitamin D3 on Calcium Retention and Egg Shell Calcification

Abstract

THE minimum requirement for vitamin D3 by the laying hen has been established but the effect of increased amounts have been only partially investigated. The minimum requirement is stated as 500 International Chick Units (I.C.U.) per kg. of feed (NAS-NRC 1966). Murphy et al. (1936) fed up to 1,550 I.C.U. per kg. of feed using fish oil as a source of vitamin D3 and concluded that the requirement level for maximum egg production and satisfactory shell quality was 780 I.C.U. per kg. However, values for percent shell increased with increasing vitamin D3 up to the highest amount fed. Couch et al. (1947) fed up to 760 I.C.U. per kg. of feed and concluded that whereas the vitamin D3 requirement for maximum egg production for layers in their first year of production was between 380 and 760 I.C.U. per kg., the requirement for hens in their second year of production was…