Magnesium in Limestones for Laying Chickens

THE BELIEF that additions of magnesium to the diet of laying chickens is likely to produce adverse effects and should be avoided, became established very early in the history of poultry nutrition. Alder (1927) reported that the use of free-choice dolomite as the only grit for Leghorn pullets resulted in decreased production, progressively thinner egg shells, and diarrhea within a period of four months. Replacing the dolomite with a high-calcium limestone corrected these ill effects. He concluded: “Since magnesium forms a part of most deposits of limestone, this product should never be used unless it is found to be free from this element.” Wheeler (1919) and Walker (1949) demonstrated that magnesium will not satisfactorily replace calcium in the diet of the laying chicken. Adverse effects on growth and bone development of chicks were noted by Buckner et al. (1932) when very high levels of magnesium carbonate (1.36 to 1.48 percent…