Tail-bone Densitometry as a Technique for Measuring Bone Mineral Status in Cattle

The paper describes the development and use of a bone densitometer (single photon absorptiometer) for the field measurement of bone mineral density in cattle. The densitometer consisted of a radioactive source of 241Americium a sodium iodide detector plus photomultiplier tube, counter and ratemeter linked to a computer. The source and detector were mounted in a “U-shaped” frame which clamped over the Cy” vertebra. A linear potentiometer measured tail thickness. Verification of the technique was carried out using postmortem material from abattoirs and spent animals for antimortem/postmortem data. Field data were obtained from a phosphorus depletion/repletion trial using mature cows. Results obtained from the abattoir experiment suggested that densitometry gave a good indication of bone ash under controlled laboratory conditions. The field data indicated that densitometry, while capable of providing a measure of bone mineral status, may not be sensitive enough to replace current methods being used. Nevertheless the results do suggest that in more sensitive animals (young growing stock) the bone densitometer may be a useful diagnostic tool.