IX. REQUIREMENTS 167 



placed at 17 to '22 l.V . per kilogram of body weight pci' day when vitamin 

 A was ted, or 20 to 30 y when carotene was fed.^ Since this level is probably 

 not ade(iuate for reproduction, the NRC subcommittee reporting on this 

 animal recommendetl an intake of 180 I.U. of vitamin A as carotene per 

 kilogram of body weight per day.-' It was the opinion of this committee 

 that this level is probably adequate also for the mule. 



7. Swine 



The daily vitamin A intake which is sufficient to prevent any detectable 

 sign of nyctalopia in swine is reported as being from 18 to 24 I.U. of vitamin 

 A or 25 to 39 7 of carotene per kilogram of body weight.- This level prob- 

 ably does not allow for adequate storage or for the demands of other func- 

 tions. The recommendation of the NRC subcommittee was 150 I.U. of 

 vitamin A as carotene per kilogram of body weight per day for growing 

 animals, 200 units for pregnant animals, and 330 units for lactating fe- 

 males." 



8. Cattle 



Cattle have been intensively studied with respect to their requirement 

 for vitamin \. The results of some of these studies are summarized in Table 

 XIX. Depending on the standard used, the requirement has been placed 

 at 25 to 150 I.U. per kilogram of body weight. The 220 I.U. per kilogram 

 of body weight per day as recommended by the subcommittees on beef 

 cattle and dairy cattle of the NRC are such as to meet the exigencies of 

 practice and hence contain a considerable margin of safety. To meet the 

 extra retiuirements of the last two months before parturition a daily intake 

 of 30 mg. of carotene is recommended.^- Such a feeding practice will assure 

 a high vitamin A level in the colostrum. 



9. Sheep 



The daily intake of vitamin A which is sufficient to prevent nyctalopia 

 in sheep is reported as 17 to 26 I.U. of vitamin A or 25 to 35 7 of carotene.'^ 

 The recommendation of the NRC subcommittee which should allow for 

 adequate storage and meet the demands of reproduction and lactation was 



21 P. B. Pearson, C. F. Winchester, and A. L. Harvey, Recommended Nutrient 



Allowances for Horses, National Research Council (U. S.), Washington, D. C, 



1949. 

 " E. H. Hughes, W. M. Booson, K. W. Crampton, and X. R. Ellis, Recommemiod 



Nutrient Allowances for Swine, National Research Council (U. S.), Washington, 



D. C, 1950. 



