REQUIREMENT FOR VITAMINS D 675 



. The Requirement for Vitamins D 



(/) In the Lower Anrmnls 



Many factors affect the amount of \itaniin D required in the diet. The 

 foremost of these factors is the extent to which the animal is exposed to 

 sunlight, and the intensity of the ultraviolet light so recei^•ed. In the 

 case of babies, the amount of clothing is also of importance, inasmuch as 

 the greater the area of exposure to sunlight, or to other sources of ultra- 

 violet light, the greater will be the amount of synthesis of vitamin D. In 

 some animals, particularly the rodents, the ratio of calcium to phosphorus 

 in the diet influences the amount of vitamin D required for optimum nu- 

 trition. Another factor which causes a variation in the quantity of vita- 

 min D required is the extent to which phosphate is available. Zucker and 

 co-workers ^'*^ observed that the greater the acidity of the diet the less 

 rachitogenic it becomes. This effect is presumably ascribable to the re- 

 sultant increase in solubility of calcium and of phosphate with increasing 

 acidity. However, Shohl ef al. '^^ were unable to demonstrate any difference 

 in the action of phosphate on rickets in rats, regardless of whether it was 

 included in the diet as the acid, neutral, or alkaUne salt. Anah'sis of 

 bones showed the greatest ash deposition following neutral diets, less 

 deposition with alkaline diets and least with acid diets. 



Although the a\'erage requirement for vitamin D in the case of A'arious 

 domestic animals can only be a matter of conjecture, the Committee on 

 Animal Nutrition of the National Research Council (U.S.)-^^'^ has set up 

 tentative standards. 



a. Chickens and Poultry. The amount of vitamin D recommended 

 varies with age. The following amounts of vitamin D (AOAC units/lb. 

 of feed) are set for chickens of these different groups: starting chicks (0 

 to 8 weeks), 180; growing chicks (8 to 18 weeks), 180; la5dng hens, 450; 

 and breeding hens, 450. Table 7 gives a more exact evaluation of the 

 requirement of chickens of different sizes and breeds. •^■'^•^*^ 



^■^ T. F. Zucker, W. C. Johnson, and M. Barnett, Proc. Soc. Exptl. Biol. Med., 20, 20-22 

 (1922-1923). 



3^' A. T. Shohl, H. B. Bennett, and K. L. Weed, ./. Biol. Chem., 78, 181-190 (1928). 



^*^ Anonymous, Nat. Research Council, Comm. Animal Niitrition, Nutrient Require- 

 ments for Domestic Animals, No. 1. Nutrient Requirements for Poultry, revised, 1954; 

 No. 2. Nutrient Requirements for Swine, revised, 1953; No. 3. Recommended Nutrient 

 Allowances for Dairy Cattle, revised, 1950; A"o. 4- Recommended Nutrieyit Allowances for 

 Beef Cattle, revised, 1950; No. 5. Recommended Nutrient Allowances for Sheep, revised, 

 1949; No. 6. Recommended Nutrient Allowatices for Horses, 1949: No. 7. Nutrient Re- 

 quirements for Foxes and Minks, 1953; No. 8. Nutrient Requirements for Dogs, 1953; 

 No. 9. Nutrient Requirements for Rabbits, 1954. 



^^'J. H. Jones, Vitamin D. Group. VIII. Requirements. A. Of Animals, in W. H. 

 Sebrell and R. S. Harris, The Vitamins, Vol. II, Acad. Press, New York. 1954, pp. 253- 

 256. 



