Quite often the ash content of the (defatted) bone is taken as a measure of the mineral content of broiler bones.

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Placed in a laboratory oven, then measured the amount of calcium

After ethical slaughter a 10-20 gram piece of long bone can be collected from the broiler bird. After initial heating it in a 25 or 50 ml silica crucible to remove moisture, it can be ashed in a muffle furnace and cooled in dessicator. Of course you have take initial and final weights. Calcium can be estimated by Talapatra (1940) method and Phosphorus by spectrophotometric method

https://www.ncbi.nlm.nih.gov/pubmed/22225247