THE literature of the last several years contains anumber of reports dealing with the effects of high levels of dietary calcium (3.0 percent or more) on the performance of laying chickens. According to most of those reports, shell quality (strength, thickness, specific gravity, or percent of shell) is improved as a result of feeding diets containing levels of calcium higher than formerly recommended (2.25 percent) by the National Research Council (1960). Improvement in shell quality was noted by Petersen et al. (1960), Mostert (1960), Durham et al. (1960), Thornton (1960), Pepper et al. (1961), Harms and Waldroup (1961), Mueller (1961), Arscott et al. (1962), Sullivan and Kingan (1962), Hinners et al. (1963), and Reddy and Sanford (1963). Yates and Schaible (1960) and Wilkinson (1961), however, observed no significant improvement in shell quality as a result of feeding diets containing, respectively, 3.5 and 3.0 percent of calcium in comparison with diets…
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Arnon L. Mehring (1965) studied this question.