Effects of Excess Calcium on a Fluoride-Magnesium Interrelationship in Chicks

Abstract

The effects of excess calcium on the previously reported fluo ride-magnesium interrelationship were studied using a factorial arrangement of treatments involving two levels of calcium (1.0 and 1.67%), two of fluoride (0.005 and 0.085% ) and two of magnesium (0.07 and 0.47% ). As noted earlier, growth rate was reduced by fluoride alone, but was reduced to a much greater extent with fluoride plus magnesium. Magnesium alone did not influence growth rate. Excess calcium improved growth in chicks fed fluoride alone or fluoride plus magnesium, but growth rate was still inferior, particularly in the fluoride plus magnesium group, to the control or the diet containing magnesium alone. Growth rate was not affected by calcium level in chicks fed the other diets. Bone ash was increased with fluoride alone, reduced slightly with magnesium alone and reduced greatly by the combination of fluoride and magnesium. Excess cal cium increased bone ash only slightly in chicks fed high magnesium alone or in combination with fluoride. The characteristic leg weakness observed in chicks fed the high fluoride-high magnesium diet was not influenced by dietary cal cium. Excess calcium drastically reduced the fluoride content of plasma and bone of chicks fed the high fluoride diets. High dietary calcium also reduced plasma magnesium levels in chicks fed high magnesium diets. From these re sults, it was concluded that the beneficial effects of excess calcium on the fluo ride-magnesium interrelationship are mediated primarily through reduced ab sorption of fluoride, and possibly magnesium, rather than through correction of a relative calcium deficiency. J. Nutr. 102: 1699-1708, 1972. Earlier studies showed that feeding pens in electrically heated, wire-floored chicks high levels of both fluoride and mag- chick batteries. Each of the eight experi- nesium resulted in a greater depression mental treatments was assigned to four in growth than observed in chicks fed pens (replicates) of 10 chicks each with fluoride alone, and produced a character- the restriction that no replicate of the same istic leg weakness and reduced bone ash treatment could appear in the same battery not observed in chicks fed either fluoride or the same deck level, or magnesium alone (1â€5).Increasing die- The treatments were arranged factori- tary phosphorus (1) or calcium (2) had ally with two levels of calcium (1.0 and some beneficial effect in alleviating certain 1.67%), two of fluoride (0.005 and symptoms of the high fluoride-high mag- 0.085% ) and two of magnesium (0.07 nesium interrelationship, but did not cor- and 0.47% ). An increase of 0.67% cal- rect the condition. The purpose of the prA¨s- cium in the high calcium diet was chosen ent investigation was to investigate the since this level is equivalent on a gram mechanism by which increasing dietary molecule basis to 0.4% of magnesium, the calcium exerted a beneficial effect. increment used to produce the high mag nesium diet. The diets used were the same EXPERIMENTAL PROCEDURES