Comparison of Methods to Evaluate Bone Mineralization

Extraction of lipid from tibias of broilers in the Association of Official Analytical Chemists-recommended procedure is often a rate-limiting step in evaluation of bone mineralization. In addition, environmental concerns may limit the use of solvents to extract lipids. A study was conducted to compare various alternative methods of evaluating bone mineralization in young (0 to 21 d) broiler chicks. Male chicks of a commercial broiler strain were fed diets ranging from deficit to surfeit in supplemental phosphorus. At 21 d, all surviving birds were killed. From each bird, the toes were removed from the right leg, and the foot (from the tibiotarsal junction) was removed from the left leg. After drying, these were ashed with no lipid extraction. Tibias from the right leg were taken and subjected to lipid extraction prior to ashing; tibias from the left leg were ashed without lipid extraction. Estimates of phosphorus requirements by nonlinear regression using each of the measurements resulted in similar values. A high correlation existed between each of the alternative measures and values from extracted tibias, with unextracted tibia ash appearing to have the highest relationship (R2 = 0.95) followed by foot ash (R2 = 0.92) and toe ash (R2 = 0.88). Considerations for using any of these alternative methods are the greater amount of organic matter that is burned off in ashing, which might create problems with alarm systems in laboratories, possible differences in lipid metabolism due to nutrition, disease, or other factors, and effect of age of the chick.