Apparent ileal digestibility of calcium in limestone was determined in broilers using the direct method.
Calcium digestibility coefficients of the three limestone samples ranged from 0.54 to 0.61.
Increasing the dietary phosphorus concentration from 0 to 4.5 g/kg increased the apparent ileal calcium digestibility of limestone from 0.56 to 0.60.
Further studies are needed to determine the calcium digestibility of other commonly used calcium sources.