The Influence of Dietary Factors on Egg Shell Quality.

CONSIDERABLE data have been reported on the necessity of supplying supplemental calcium to laying hens. Collier (1892), by the use of balance experiments, showed the necessity of supplying extra calcium to laying hens and the value of oyster shell as such a supplement. Most of the material reported has dealt with the relative efficiency of different calcium supplements fed ad libitum. Very few data are available in the literature on the calcium requirements of laying hens, and those available are controversial. Norris, Heuser, Ringrose, and Wilgus (1934) reported that l.5 percent calcium was not sufficient for heavy egg production, 1.65 percent appeared just adequate, and 1.80 percent was optimum. Mitchell and McClure (1937), assuming 50 percent production and 50 percent utilization of dietary calcium, calculated that 2.74 percent of calcium would be necessary in the diet. Titus, Byerly, Ellis, and Nestler (1937) recommended a level of 2.2 percent in the . . .