The Effect of Magnesium in Limestone on the Growth and Tibia Ash of Chicks

MAGNESIUM is present in varying quantities in different limestones, and it has been thought that if limestones containing the higher levels of magnesium were used as a source of calcium in the diet of growing chickens undesirable effects would be produced. Both Buckner et al. (1932) and Milby (1934) observed adverse effects in chicks fed diets supplemented with magnesium carbonate in sufficient quantity to raise the magnesium level of their diets, respectively, to 13,600 and 8,900 p.p.m. These levels of magnesium, however, are higher than would result from the addition to the diet of any of the commonly available limestones as a source of calcium. Gardiner et al. (1960) added sufficient magnesium carbonate to a purified diet for chicks to raise its magnesium content to 4,058 p.p.m., but observed no undesirable effects. Keene and Combs (1962) added as much as 2,000 p.p.m. of magnesium (as magnesium carbonate) to a corn-soy…