578 IX. CAROTENOIDS AND VITAMINS A 



have been among the criteria used;^^^ Sherwood and Fraps^''^ inckided fer- 

 tility and egg production as well. The quantity of vitamin A necessary to 

 prevent or cure night blindness was employed by Guilbert et al^'^^ to ascer- 

 tain the vitamin A requirement of swine, cattle, sheep, and horses. The 

 dark adaptation test is an application of a similar physiologic condition 

 in man^®""^^* which is widely used for a clinical evaluation of the vitamin A 

 requirement. Lactation is a criterion employed for the evaluation of the 

 vitamin A requirement of sheep^''^-^^'' and of horses. ^^^ 



{2) Factors Altering the Requirement for 

 ^-Carote7ie and for Vitamin A 



a. Species. If the vitamin A requirement is based upon the amount 

 necessary for the whole animal to satisfy its daily vitamin A needs, it is 

 obvious that marked variations will obtain, according to the size of the 

 animal. Guilbert and Hart^^'' first called attention to this point in 1935, 

 and subsequent studies have confirmed and strengthened the hypothesis. 

 As in other biometric phenomena, it seems that vitamin A requirements 

 might be more uniform in different animals with wide ranges of body weight 

 if expressed on the basis of surface area rather than on that of body weight. 



According to the summary of Mattson,''^^ the average minimum daily 

 requirement to support growth and to prevent gross symptoms of defi- 

 ciency in mammals is 24 /ig. of /3-carotene (40 I.U.) or 20 I.U. of vitamin A 

 per kg. of body weight. When the figure is based upon storage, reproduc- 

 tion, and lactation, considerably higher values are observed for the vitamin 

 A requirement. The proportion of carotene or of vitamin A required by 

 chickens and turkeys is considerably higher than that needed by mammals. 



958 H. J. Almquist and E. Mecchi, Poultry Set., 18, 129-137 (1939). 



959 R. M. Sherwood and G. S. Fraps, Texas Agr. Expt. Sta., Bull. No. 573, 5-21 

 (1940). 



^^ S. Hecht and S. Shlaer, J. Opt. Sac. Amer., 28, 269-275 (1938). 

 9" J. M. Lewis and C. Haig, J. Pediat., 15, 812-823 (1939). 



962 L. E. Booher and E. C. Callison, /. Nutrition, 18, 459-471 (1939). 



963 E. L. Batchelder and J. C. Ebbs, /. Nutrition, 27, 295-302 (1944). 



964 E. M. Hume and H. A. Krebs, Vitamin A Requirement of Human Adults. An 

 Experimental Study of Vitamin A Deprivation in Man (A Report of the Vitamin A 

 Subcommittee of the Accessory Food Factors Committee), Med. Research Council (Brit.), 

 Spec. Rept. Ser. No. 264 (1949). 



966 p. B. Pearson, H. M. Briggs, W. G. Kammlade, J. I. Miller, and R. F. Miller, 

 Recommended Nutrient Allowances for Domestic Animals. V. Recommended Nutrient 

 Alloivanc.es for Sheep, Committee on Animal Nutrition, Nat. Research Council, Washing- 

 ton, D. C. (1945), pp. 1-20. 



966 H. R. Guilbert and J. K. Loosli, J. Animal Sci., 10, 22-41 (1951). 



967 H. R. Guilbert and G. H. Hart, J. Nutrition, 10, 409-427 (1935). 



