Calcium tolerance of growing chickens: effect of ratio of dietary calcium to available phosphorus

Excess calcium intake has been shown to reduce growth and feed efficiency and to increase bone ash and bone strength in growing chickens. Source and level of dietary phosphorus have been shown to affect calcium tolerance. The effects of high calcium can be largely explained by its effects on intestinal pH. The proposed mechanism involves excess calcium reducing the soluble fraction of minerals and the proportion of minerals in small complexes. In consequence, their availability for absorption is probably also reduced. The growth depression of chickens fed on diets high in calcium may be partly caused by the decreased availability of other minerals needed for growth. Calcium tolerance of growing chickens may be increased by ensuring that there are higher than normal levels of the other required minerals in the diet.