Whenever a group of equine nutritionists get together (like at a recent Kentucky Equine Research conference where much of this was discussed), one thing we always tend to discuss is the amount of misinformation that is out in the horse world. We like to chat about products and companies that sell supplements that have misleading claims, or incorrect labels, or with questionable ingredients.
A newer trend that we’ve discussed is the numerous companies that try to sell horse owners a ‘Quick Fix’; that is, they sell different types of tests that try to tell you what your horse needs in their diet and management, without there being significant evidence that they work.
One type of test that is available is a hair analysis, that intends to analyze the mineral content of your horse’s hair and, by inference, determine if your horse’s diet is balanced for minerals. Of course, these companies also try to sell you products to meet your horses’ deficiencies.
There are very few scientific studies that have examined mineral content of hair, and with the exception of heavy metals that might accumulate over time (arsenic for example), research suggests that environmental contamination of the hair invalidates almost all correlation with body mineral content. In fact, if you were to send in two samples of the same one horse’s hair, but naming them as different horses with different histories and diets, you would get two very different analyses and feeding recommendations. I welcome any of you to try that fun experiment!
It may also be suggested to have your horse’s blood analyzed to determine any nutrient deficiencies. Short of a few nutrients, the body does a very good job of maintaining blood nutrition concentrations within a certain range. For example, blood calcium concentrations are maintained by two hormones, such that if blood calcium decreases, the body will remove calcium from the bone and put it into the blood to try to maintain blood calcium concentrations. So if you were worried about calcium, you might think your horse was fine based on bloodwork, but it may in fact have very weak bones if the diet wasn’t good!
Some nutrients may result in changes in the blood. For example, iron status may be accessed with blood ferritin concentrations (the storage form of iron), although it might not reflect actual iron intake (as most horses consume a lot of iron with few reports on elevated ferritin). Selenium status may be assessed by quantifying glutathione peroxidase activity, which is the enzyme associated with selenium’s function. Vitamin E concentrations also may be worth investigating with a blood sample, as some horses may have altered vitamin E absorption and show low blood vitamin E concentrations despite a normal dietary intake. It is easy enough to have your veterinarian add these tests (vitamin E, selenium and perhaps ferritin) to your horse’s yearly wellness blood panel, and discuss the results with your nutritionist.
Allergies may also be of concern for horse owners, and yes – there is a test for that! The skin test is the most reliable way to test for allergens, but they require clipping (which may not work for show horses) and tend to be more sensitive to environmental allergens vs. feed allergens. In fact, true feed allergies are exceedingly rare in horses, although horses may be sensitive to some foods (but not a true allergy). There are several companies that will analyze a blood sample and name the allergens your horse is sensitive to, with some also offering a series of injections for your horse to help them cope! Again – submissions from the same horse yielded different results.
While most allergies are environmental, if you truly suspect a dietary sensitivity, a withdrawal diet is the best way to determine what feed/ingredient is bothering your horse. To do this, you would remove all feed from your horse apart from some good quality hay, and feed only hay for two weeks (along with water and white salt). After that, you can add in either a different type of hay, or some grain (not introduced at the same time), and wait another two weeks. Then after two weeks you can add in another feed – until you identify the culprit.
As you can imagine, this takes some time and likely requires a horse not to be in any work (seeing as his overall nutrient intake would be limited due to hay). It also might mean trying different raw ingredients (such as straight oats or soybean meal) over a commercial feed so you can pinpoint the exact ingredient that is causing the issue. Because of this, many owners just prefer the quick blood test, even if it is not accurate.
Another evolving type of quick fix test is genetic testing. Horses do have some heritable (genetic) muscle disorders that can be diagnosed with genetic testing for specific gene mutations – for example, Hyperkalemic Periodic Paralysis (HYPP) and Polysaccharide Storage Myopathy type 1 (PSSM1). Unfortunately, there are some emerging muscle disorders that may have a genetic basis, but the gene in question has not been identified. There have been some genes that may show variation within a population (for example, a group of horses with some muscular disorder symptoms – like reluctance to work, muscle twitching or muscle wastage), but without a true genetic mutation identified, these markers are not specific to a true disease state.
There are a few excellent genetic testing facilities including one at the University of California at Davis, as well as the Neuromuscular Disease Laboratory at the Royal Veterinary College in the UK. However, there are several commercial laboratories offering diagnostic testing of muscle disorders that do not use peer-reviewed scientific data. These companies can potentially cause issues for breeders and buyers, because it leads to a lot of misinformation and confusion. One muscular term used by one such company is “muscle integrity myopathy”, which is not actually a disease described anywhere in the veterinary scientific literature!
So how do you get the ‘quick fix’? Surprise! It is even less invasive than pulling hair, blood or even muscle: analyze your horse’s diet! It is relatively simple to work on your own (for example with a program like FeedXL) or with an independent nutritionist to evaluate your horse’s diet to see what nutrients – if any – may be lacking.
