X. EFFECTS OF DEFICIENCY 95 



tion of the National Research Council is 130 mg. %.*-" For diets containing 

 homocystine in place of methionine, 60 mg. % of betaine-irreplaceable and 

 140 mg. % of betaine-replaceable choline are required, according to Alm- 

 quist.^-^ Minimum levels of methionine and of irreplaceable choline were 

 reported as 500 and 100 mg. %, respectively, by McKittrick.^-^ West et at. 

 found 100 mg. % of choline adequate if ample methionine was provided.*^' 

 The growth-depressing action of excess methionine in chick diets was 

 counteracted by guanidoacetic acid and by serine but not by decreasing 

 dietary cystine. Excess homocystine did not depress growth unless choline 

 was also present. McKittrick also noted that betaine was a satisfactory 

 replacement of part but not of all the choline requirement. 



Although the significance of betaine-replaceable choline in the chick is 

 not readily apparent in view of the reported failure of betaine to show anti- 

 perotic activity, the distinction between the two parts of the choline re- 

 quirement has emphasized the role of B12 in this phase of avian metabolism. 

 Patton et al. noted a beneficial growth effect of fish meal in chick diets com- 

 posed mainly of corn and soybean oil meal.^^* Choline, betaine, and methio- 

 nine were also reported to have an interchangeable supplementary effect 

 in the improvement of the corn-soybean ration.^-^- ^-^ Gillis and Norris found 

 liver paste superior to supplements of choline or betaine and later obtained 

 similar results with B12 in place of liver paste.^^^ Schaefer et al. reported that 

 both folic acid and B12 decreased the choline requirement for growth. ^^^' ^^^ 

 Jukes and Stokstad demonstrated that B12 spared the choline requirement 

 for growth but not for prevention of perosis.^"^^ The response to homocystine 

 in the presence of B12 was augmented by the addition of either choline or 

 betaine. However, a supplement of methionine has been reported to decrease 

 the B12 requirement of chicks on a diet lacking animal protein.*^* Methyla- 



"0 W. W. Cravens, H. J. Almquist, R. M. Bethke, L. C. Norris, and H. W. Titus, 

 Recommended Nutrient Allowances for Poultry, National Research Council 

 (U.S.), Washington, D. C, 1944, revised 1946. 



321 H. J. Almquist, Science 103, 722 (1946). 



322 D. S. McKittrick, Arch. Biochem. 15, 133 (1947); 18, 437 (1948). 



323 J. W. West, C. W. Carrick, S. M. Hauge, and E. T, Mertz, Poxdtry Sci. 30, 880 

 (1951). 



324 A. R. Patton, J. P. Marvel, H. G. Petering, and J. Waddell, /. Nutrition 31, 485 

 (1946). 



325 J. A. Marvel, C. W. Carrick, R. E. Roberts, and S. M. Hauge, Poultry Sci. 23, 

 294 (1944). 



326 D. H. Mishler, C. W. Carrick, and S. M. Hauge, Poultry Sci. 28, 24 (1949). 



327 M. B. Gillis and L. C. Norris, J. Biol. Chem. 179, 487 (1949); Poultry Sci. 28, 749 



(1949). 



328 A. E. Schaefer, W. D. Salmon, and D. R. Strength, Proc. Sac. Exptl. Biol. Med. 71, 

 202 (1949). 



329 G. M. Briggs, E. G. Hill, and M. J. Giles, Poultry Sci. 29, 723 (1950). 



