Foot Ash as a Means of Quantifying Bone Mineralization in Chicks

Three studies were conducted to evaluate foot ash as an alternative method to quantify the degree of bone mineralization in broiler chicks. In Experiment 1, the objective was to evaluate whether degree of bone mineralization would be reflected by foot ash in broiler chickens at 14 d of age. Birds receiving 0.24, 0.32, or 0.40% of dietary available phosphorus (AP) demonstrated significant differences in foot ash (10.93, 13.46, and 15.45%, respectively). In Experiment 2, we determined that the time required for a foot sample to dry to a constant weight at 105°C was 48 h. In Experiment 3, the objectives were to compare the response of bone mineralization to dietary phosphorus levels as reflected by foot ash and tibia bone ash and to evaluate the effect of fat extraction on the determination of these parameters. Broiler chicks were fed graded levels of AP (0.25, 0.30, 0.35, and 0.40%) from 1 to 14 d of age. Significantly different responses between each dietary AP level could be detected by any method used. A significant linear response was observed between dietary AP and percentage of extracted or unextracted tibia or foot ash, with determination coefficients above 90% found for all 4 methods used. Results confirmed that the dietary phosphorus levels affected bone mineralization and that the degree of mineralization could reliably be reflected by foot ash. The assay was found to be as reliable as the tibia bone ash in reflecting degree of bone mineralization in chicks during the first 14 d of age. Fat extraction did not affect the reliability of either assay.