In a previous communication Gillis and Norris (1949) showed that certain types of practical chick rations are significantly improved by the addition of betaine or choline. However, when the basal diet contained 0.15% of an animal protein factor (APF) concentrate (Wilson and Company’s liver paste) no further response was obtained by adding betaine or choline. The APF concentrate used in this work contained approximately 17 micrograms of vitamin B12 per gram. The assumption was made that either this vitamin or some unidentified component of the APF complex exerted a sparing action on the chick’s requirement for labile methyl groups. The amount of APF concentrate used supplied only 0.0018% choline in the diet. A report of a preliminary experiment in which a purified vitamin B12 preparation was found to have the same effect as the APF concentrate was made at the Informal Conference on Poultry Nutrition held at Detroit, April 18, .