a.k.a. Bone Mineral Density (BMD) is a measurement of the relative proportion of bone mineral versus fibrous tissue matrix in boney tissue. It is an important indicator of skeletal health, strength, and resilience. Methods of measurement include X-Ray, Ultrasound, CT scanning and single photon absorptiometry.
Factors influencing BMD include age and exercise (newborn foals have low BMD at only 17% of adult values whereas yearlings may approach 87% of adult density). Training stimulates re-modelling of bone to strengthen areas under the most stress and generally results in increased BMD. Where training stresses exceed the ability of bone to withstand forces applied, fracture or microfracture may result. The ‘’shin soreness’’ common in young Thoroughbreds undergoing race training is a result of microfractures in the shaft of the cannon bone. As BMD increases during training such damage becomes less likely. Stabling a horse even for a week without access to exercise will significantly reduce BMD even when dietary minerals are plentiful. Dietary mineral intake will influence BMD only when bone is being actively re-modelled, that process being driven primarily by sufficient fast work. Increasing Calcium & Phosphorous intake to support rising BMD during training of 2-year-old Thoroughbreds is desirable, along with the use of Omega 3 supplements like flaxseed oil which has been shown to improve the Calcium absorbtion and retention rates.
