Apparent ileal digestibility of calcium in limestone for broiler chickens

Abstract

The objective of the study that is presented herein was to determine the apparent ileal calcium (Ca) digestibility of limestone for broiler chickens as influenced by limestone source and dietary phosphorus (P) concentration. Limestone from three commercial sources (coded as LM-1, LM-2 and LM-3) were obtained, ground to pass through a 0.2mm sieve and analysed for mineral composition and in vitro solubility. Analysed Ca concentration and in vitro solubility coefficient of LM-1, LM-2 and LM-3 were 410, 390 and 420g/kg, and 0.28, 0.29 and 0.27, respectively. Two experimental diets, containing 9g/kg Ca, were developed from each limestone source with 0 and 4.5g/kg dietary P. Titanium dioxide was incorporated as an indigestible marker. Each experimental diet was then randomly allotted to six replicate cages (eight birds per cage) and fed from day 21 to 24 post-hatch. Apparent ileal digestibility of Ca was calculated using the indicator method. Apparent ileal Ca digestibility coefficients of LM-1, LM-2 and LM-3 were determined to be 0.58, 0.61 and 0.54, respectively. Calcium digestibility of LM-3 was lower (P<0.05) than LM-2 but similar (P>0.05) to LM-1. There was no difference (P>0.05) between the Ca digestibility of LM-1 and LM-2. Increasing the dietary P concentration from 0 to 4.5g/kg in assay diets increased (P<0.05) the average Ca digestibility from 0.56 to 0.60.