is considered by many nutritionists/scientists/vets to be very limited for overall nutrient balance. Nutritionists can’t use results for balancing a horse’s intake or consider hair testing credible in the face of such significant research.
Hair can be analysed for a variety of substances, including drugs, but in nutritional terms hair analysis refers to hair mineral levels. Minerals reach hair via the blood so it’s going have similar limitations as blood testing since hormones control the levels of many of the minerals giving little indication of the status for the rest of the body. Dr Kellon VMD “Hair mineral is not an accurate way to determine mineral status and is worthless for formulating the diet and supplements.” NRCPlus.
The kidneys will rapidly excrete minerals when they are higher than a tight range, electrolytes like potassium are a good example. The liver can remove minerals before they reach hair. Hair testing can’t tell mineral balance even if the totals were credible as it doesn’t indicate whether it’s due to a deficiency in the first place or competition with another mineral or the body had a high need at that time. This more recent study in 2022 compared mineral levels in hair to the liver. The liver is the gold standard to determine body status of mineral levels but of course, dire for the horse. Evaluation of hair analysis for determination of trace mineral status and exposure to toxic heavy metals in horses in the Netherlands found that “Our results do not support the use of hair to determine mineral status in the horse ..”
Hair can be useful for some heavy metals and selenium but from a nutrition point of view hair testing is not considered overall to be reliable.
Selenium may be an exception according to a 2014 study Analysis in horse hair as a means of evaluating selenium toxicoses and long-term exposures. Their results demonstrated that in *some cases* hair samples can be used to determine selenium exposure in horses up to 3 years postexposure.
Selenium results via hair testing is debated. Veterinarian and nutritionist Dr Sarah Ralston has concerns. Ralston, a faculty member at Rutgers University, agrees that hair analysis may be “vaguely useful” for selenium status, but believes values from blood samples are more representative of true levels. Dr Eleanor Kellon VMD recommends a whole blood sample.
Equine Hair Analysis
With selenium the result can’t tell us:
There’s been many studies which have demonstrated that many factors other than diet affect the mineral concentrations in hair. Things that affect the mineral levels in hair testing include the time of year, location on the body (different parts of the body test differently, even if they are the same hair colour), breed, age, hair colour, shampoo residues, airborne contamination, sweat, dust on the horse, soil on the horse (even if the horse looks clean), all make a difference. It’s not uncommon for hair mineral analyses can’t tell the difference between minerals that are on the surface of the hair and those that are actually inside the hair.
One study found higher concentrations of zinc in different colours of hair on the same animal. The same colour hair on different breeds of cattle eating the same food and in the same paddocks produced different mineral levels. Researchers found the age of calves/cows in the same paddock eating the same feed tested for different levels of minerals. Researchers found differences in mineral content of calf hair in calves by different sires – calves were all together and being fed same food. Animals tested all year round showed different mineral level at different times of year, even though they were eating the same thing. There has been more success with hair testing for arsenic and cadmium, but even such things as age, sex, and length of hair, have been demonstrated to affect the testing for arsenic.
One vet researcher sent hair from one horse as separate samples and got very different results. Dr Eleanor Kellon discusses the limitations of hair testing in NRCPlus and Dr Ann Nyland researched this in great detail in her book ‘Natural Horse Care The Right Way’.
There is a huge body of research on hair analysis, and not one scientific paper has found any evidence that it is in any way effective for balancing the intake (that I know of).
A 2015 study by A Ghorbani et al compared blood testing vs hair testing which found (not surprisingly) that hair testing was superior to blood testing. Since we know that blood testing is extremely limited it’s not saying much about the validity of hair testing.
When published it did cause a stir stating “Hair mineral analysis is a suitable tool for evaluating mineral status in horse.” Unfortunately the study design didn’t compare with liver nutrient status so wasn’t able to verify hair levels with body levels of nutrients. The statement that hair testing is a suitable tool is a stretch.
The best and most accurate approach is to have the intake tested (pasture/hay and so forth) and the diet balanced. It’s not an exact science but the best we have other than a liver biopsy! Soil testing is valuable for long term soil treatment and improving pastures but not useful for determining what is in your horse’s intake. Read more about soil testing and pasture or hay testing.
Links may change over time. If a link doesn’t work, search the title in your search engine.
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Can hair analysis determine what supplements a horse needs?
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