Ensuring your horse is getting all of his required nutrients is important for his overall health and nutrition. As a nutritionist, I feel the best way to determine if a diet is meeting a horse’s nutritional needs is to evaluate the diet for nutritional content. However, a recent study out of Iran sought to determine if dietary mineral intake resulted in changes in serum and hair mineral composition (Effect of Dietary Mineral Intake on Hair and Serum Mineral Contents of Horses; Ghorbani A., Mohit A. and Kuhi HD. Journal of Equine Veterinary Science, 2015).
In this study, researchers fed horses diets that were supplemented with a mineral source or were not supplemented, coupled with being fed the base diet at 100 per cent of recommended intake or 50 per cent of recommended intake (i.e. In the 50 per cent diet, they were fed 50 per cent fever calories, protein, etc.).
The diets had very little impact on serum mineral status, even when horses were fed significantly deficient diets (in all nutrients), reminding us the robust ability of the body to maintain blood concentrations through homeostasis under periods of nutritional stress (and thus showing that a blood sample is not very effective at diagnosing a nutritional deficiency!).
There did appear to be an effect of diet on hair mineral content, with horses being fed restricted levels of nutrition having lower concentrations of several nutrients in their hair, including several of the major minerals (eg. Calcium, phosphorus, magnesium and sulfur). Major minerals are also easily measured in feed. Therefore, it is likely of more interest the relationship between intake and hair content for some of the trace minerals that might be more difficult to test for in the diet (such as selenium, iodine and cobalt, as iron, copper, zinc and manganese are also found on feed analysis). There did appear to be a relationship between dietary intake of cobalt and manganese on hair concentration. However, there was also a variation in hair selenium content, despite two groups each having the same selenium intake. The authors also report varying concentrations of nickel, aluminum, and lead.
While these findings are indeed interesting, it appears that there are also non-nutritional impacts on hair content. A low mineral value on a hair analysis report should indeed be interpreted with caution and does not necessarily imply a nutritional deficiency. A thorough nutritional evaluation would likely pinpoint any deficiencies in the diet, but a hair analysis may help to confirm such a finding.