IX. REQUIREMENTS 169 



placed at GOO to 930 I.U. of vitamin A, as carotene, per kilogram of body 

 weight. The growth reciuirenicnt was estimated as 220 units.'^ 



10. Chickens 



The requirements of both growing chicks and laying hens have been 

 intensively investigated. The criteria used, and the intake recommended 

 by several investigators, are summarized in Table XX. With a few excep- 

 tions, the levels recommended have l)een quite consistent for a particular 

 criterion. Under proper feeding conditions, the levels recommended by the 

 NRC subcommittee, 2000 I.U. per pound of feed for growing chicks and 

 3300 I.U. for laying and breeding hens, should prove adequate. 



" J. iM. Lewis and L. T. WiKson, J. Nutrition 30, 467 (1945). 



2^ H. A. Keener, S. I. Boclulel, N. B. Guerrant, and W. T. S. Thorp, J. Dairy Sci. 25, 

 571 (1942). 



"J. H. Jones, J. K. Riggs, G. S. Fraps, J. M. Jones, H. Schmidt, R. E. Dickson, 

 P. E. Howe, and W. H. Black, Proc. Am. Soc. Animal Production 31, 94 (1938). 



*« L. L. Madsen, O. N. Eaton, L. Heemstra, R. E. Davis, C. A. Cabell, and B. Knapp, 

 /. Animal Sci. 7, 60 (1948). 



" L. A. Moore, J. F. S.ykes, W. C. Jacobson, and II. G. Wiseman, ./. Dairy Sci. 

 31, 533 (1948). 



"P. D. Boyer, P. 11. Phillips, N. S. Lundquist, C. W. Jensen, and I. W. Rupel, 

 J. Dairy Sci. 25, 433 (1942). 



" A. H. Kuhlman and W. D. Gallup, ./. Dairy Sci. 25, 688 (1942). 



'"J. K. Loosli, C. F. Huffman, W. E. Petersen, and P. II. Phillips, Recommended 

 Nutrient Allowances for Dairy Cattle, National Research Council (U. S.), Wash- 

 ington, D. C, 1950. 



" H. R. Guilbert, P. Gerlaugh, and L. L. Madsen, Recommended Nutrient Allow- 

 ances for Beef Cattle, National Research Council (U. S.), Washington, D. C, 

 1950. 



'^ P. B. Pearson, W. G. Kammlade, J. I. Miller, and R. F. Miller, Recommended 

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

 D. C, 1949. 



"H. J. Almquist, T. H. Jukes, and W. E. Newlon, Calif. Agr. Extension Circ. 108 

 (September 1940) . 



" G. E. Bearse and M. W. Miller, Poultry Sci. 16, 34 (1937). 



35 C. F. McClary, V. L. Miller, and G. E. Bearse, Western Wash. Expt. Sta. Bull. 

 (December 1942). 



36 M. W. Taylor and W. C. Russell, Poultry Sci. 26, 234 (1947). 

 " R. E. Gray and H. E. Robinson, Poultry Sci. 20, 36 (1941). 



3» R. M. Sherwood and G. S. Fraps, Texas Agr. Expt. Sta. Bull. 583, (1940). 



" E. L. Johnson, C. W. Carrick, and S. M. Hauge, Poultry Sci. 27, 308 (1948). 



« D. W. Bolin, C. E. Lampman, and L. R. Berg, Poultry Sci. 22, 348 (1943). 



"W. W. Cravens, H. J. Alnujuist, R. M. Bethke, II. R. Bird, and L. C. Norris, 



Recommended Nutrient .MIowances for Poultry, National Research Council 



(U. S.), Washington, D. C, 19.50. 

 « M. W. Taylor, J. R. Stern, and W. C. Russell, Poultry Sci. 26, 243 (1947). 

 " H. J. Almquist and E. Mecchi, Poultry Sci. 18, 129 (1939). 

 ** M. Rubin and H. R. Bird, Maryland Agr. Expt. Sta. Bull. A-12 (1942). 



