EXPERIENCE at the Wisconsin Experiment Station has shown that when chicks are hopper-fed chick size limestone grit or chick size oyster shell the consumption will vary from 1 to 4 percent of the ration. Chicks receiving an insufficient amount of vitamin D will consume more calcium carbonate grit than will those having access to direct sunshine or those receving an ample amount of vitamin D as supplied by cod liver oil or other vitamin D oils.Halpin (1926) reported that chicks reared inside, fed rations containing and addition of approximately 3.6 percent limestone, weighed 509 grams at ten weeks whereas those receiving no limestone averaged only 353 grams. Later experience, however, demonstrated that 2 percent of a calcium carbonate carrier in the usual chick ration was sufficient.Herrick, Ott, Halpin, and Holmes (1935) reported preliminary results which indicated that rations, high in calcium carbonate, increased the susceptibility of chickens to .