I always get excited when I learn new things, especially when I thought I knew a subject. It was the case when I started taking equine nutrition courses. Far be it from me to tell you how to feed your horse, I just wanted to share a few insights on what I discovered.
What does ''balanced diet'' actually mean?
For a few decades, the National Research Council has been working on determining the nutrient requirements for horses. The document is regularly updated in order to include the latest scientific research (6 updates so far). It is a detailed guide meant to recommend calories, minerals and vitamins intakes, depending on the horse's age, weight, working class, etc. Feeding the right amount of calories is not usually an issue. Feeding enough of a specific mineral would not be complicated either.
But here is the thing: minerals compete with one another for absorption. For example, too much iron decreases copper absorption (copper is essential for healthy joints, brain and hooves, among many other functions). Which is why, in addition to amounts, the NRC recommends ratios for minerals, in order to prevent interference. This is what ''balancing a diet'' means: ensuring that nutrients are given in right amounts AND in proportions that will allow the horse to benefit from them all.
Building the diet
The ability to feed a balanced diet depends strongly on the knowledge of your horse's needs, the ratios but also the nutritional contents of what you feed it.
Nowadays, most horse and barn owners feed their horses this way: constant supply of clean water (we all agree on that!), commercial concentrates (chosen because they're popular or recommended by someone else), about 1% if the horse's body weight in hay (it has to smell good and be pretty) and adding supplements when a problem arises (joints, digestive issues, etc.). Then if the horse is too fat, grain is cut back, if the horse is too skinny, more grain is added.
Now that you have read the previous paragraph, you understand why adding more concentrates and supplements without knowing their nutritional content (nor your horse's actual needs) may in the end do more harm than good, as well as lead to unnecessary expenses.
What happens when we don't balance minerals
An unbalanced diet can affect the muscles, joints, bone density, hoof and coat quality, energy levels, performance, gaits, immune responses, blood balance and cardiovascular health. It can also worsen metabolic problems.
Let's go back to the iron example: let's say that you live in an area where hay contains high levels of iron (like the Ottawa valley). You add a feed or balancing supplement that contains even more iron. Then you give your horse a hoof supplement (which contains manganese, which increases iron absorption/decreases copper absorption) because his feet are starting to crack and flare.
If you just looked at the copper requirements for your horse, it is probably ingesting the recommended amount. But there is so much competition from iron that your horse becomes unhealthy (iron increases insulin resistance FYI). Also, the horse has no efficient way of excreting excess iron; it is stored in the liver, which in the long run might become overloaded.
Too much versus not enough
Now that you understand the importance of ratios, you also need to understand the risk associated with the ''if a little is good, then more is better'' approach. Toxic levels have been determined for most minerals and vitamins. Below are a few examples.
Selenium is a very potent antioxidant. Low levels can cause muscle soreness, anemia and impaired immune functions. Overload can cause inflammation, sloughing of the hooves and can even be fatal if acute.
Potassium is sufficient in most equine diets. Deficiency tends to come from sodium deficiency: the kidneys excrete potassium when sodium levels are too low. Potassium is crucial to muscles and nerves; both deficiency and excess can cause weakness, tying-up, nerve irritability and even paralysis.
Magnesium deficiency can cause muscle spasms, stilted gaits, difficulty turning or cantering. Excess magnesium can impair the heart, kidneys and GI tract. If supplementing magnesium oxide, be aware that it is a hidden source of iron!
Starting to realize the risks associated to supplementing ''loosely''?
Assessing your own horse
I grew up in France, where the ideal horse in terms of body condition was the high level eventer. As a result, my definition of ''fat'' is quite different from that of most Canadians, but this is not the point! There is a tool to assess a horse's body condition score: the Henneke horse body condition scoring system. It was created by Henneke et al. (1983) at Texas A&M University and is 100% objective.
Fat horses need to be addressed seriously. In addition to cardiovascular problems, being overweight put extra strain on the joints and has negative repercussions on the horse's largest organ: the skin. By the way, hooves ARE skin!
Bottom line is: if your horse scores around 5, has a shiny coat, healthy hooves and moves/performs well, it is most likely getting everything it needs from its diet.
Does your horse really need grain?
Horses in light and moderate work don't usually need added grain or concentrates.
According to the 2007 NRC Recommendations, light and moderate work are as follows:
Light: Mean Heart Rate: 80 beats/minute. 1 to 3 hours per week; 40% walk, 50% trot, 10% canter
Moderate: Mean Heart Rate: 90 beats/minute. 3 to 5 hours per week; 30% walk, 50% trot, 10% canter, 5% low jumping, cutting or other skill work.
Most of the horses I am working with fit in those two categories. They do well on hay and a balanced mineral/vitamin supplement.
The risks related to concentrates
Very few brands actually communicate the detailed list of ingredients and nutritional analysis of their products. There is partial information on their websites, but that's it. ''Lower sugar content'' does not tell you how much sugar there was nor is (which can be very problematic if your horse is insulin resistant or Cushings). ''Added selenium'' neither, and depending on your hay, you might or might not want too much of it.
The best approach when purchasing commercial feeds is to educate yourself so that you are better able to discuss your horse's diet in depth with the sales representatives.
What you can do
The only way to know what is in you hay or pasture is to have it tested. If it's not a possibility, you can ask your chamber of agriculture for regional tendencies.
Nutrition is not at the source of every issue nor does it solve them all. You should consult your vet for any health-related issue.
Reliable sources for equine nutritional recommendations include scientific research, independent nutritionists, laboratories such as Equi-Analytical and courses such as the ones offered by Dr Kellon. Her blog provides as wealth of information, as well as the incredibly resourceful website Equine Cushings and Insulin Resistance Group, aimed at helping owners of horses with metabolic problems. Many hoof professionals are also very knowledgeable, because they are aware of the tight relation between hoof health and proper nutrition.
Conversely, be careful when reading generic blogs, articles, commercial documents and posts on social media, especially when they do not contain any scientifically-sourced information.
Also remember that there is no ''one size fits' all'' and that your horse is unique: a single article cannot determine what to feed your horse, there are way too many parameters to take into account.
Thank you for reading!