Studies in Mineral Nutrition of Laying Hens.

Factors Affecting the Transfer of Calcium (45 Ca) from the Hen’s Diet to the Egg Shell

“…There is, however, considerable variation in the findings of different investigators. Norris et al (1934), Titus et al (1937), Gutowska and Parkhurst (1942), and Berg et al (1944) have suggested dietary calcium requirements which varied between 1.6 and 2.1 percent. Later investigators, Petersen et al (1960), Durham et al (1960), Harms and Waldroup (1961), Balloun and Marion (1962), and Reddy and Sanford (1963) have shown that higher dietary calcium levels (2.75 to 4.60 percent) were more effective in improving egg shell quality.…”

Method for improving egg‐shell strength by selection12

“…Direct comparison of these results with those by others is difficult because the eggs of this study were from hens 55 weeks of age, whereas, the age of hens from which eggs were obtained by other researchers was not reported or was not constant. A greater breaking force would be expected from hens of younger ages as Gutowska and Parkhurst (1942) and Heuser and Norris (1946) have shown that shell strength decreases with increased age of hen. Significantly greater breaking force and energy in shell deformation (P<0-05) was required by eggs from the low breakage line than from their contemporaries of the high breakage line.…”

The Influence of Dietary Factors on Egg Shell Quality.

“…Losses in albumen index occurred at the 1.5 and 2.5 percent levels of calcium. Gutowska and Parkhurst (1942) fed Rhode Island Red pullets for six months on diets containing 2.35, 2.77, and 3.95 percent calcium. This gain was due to decreased production, since it has been observed by Miller and Bearse (1937) that a hen produces eggs with a higher albumen index when she is laying only a few eggs than when she is in heavy production.…”