Mineral Deficiencies
A few commonly encountered problems that may have their roots in mineral deficiencies, or imbalances that can create deficiencies even when minerals are present in their minimum recommended amounts, include:
We looked at the calcium, phosphorus, copper, zinc and selenium figures for three nationwide hay samples and saw what happens combining 22 lbs. of these hays with 2, 5 and 10 pounds of a feed with a mineral profile that represents some middle-of-the-road minimum figures common in commercial premium horse feeds. Note: Calcium:phosphorus ratios of as high as 6:1 are reported to be tolerated as long as phosphorus intake is adequate, at least short term. However, long-term effects of this and other mineral excesses on absorption of other minerals has not been studied.
When fed at 2 lbs./day, the horse still falls short for individual minimum requirements for at least one mineral with all these hay types. At 5 lbs./day, individual minimums are met for the minerals we have information on, at least for maintenance, so the "One-A-Day" concept is met. However, we still don't know the status of magnesium, iron, manganese, iodine and cobalt, and we can't be sure these numbers are accurate because the feed analyses are in terms of minimums, not actual content.
Remember, too, that the mineral ratios are important. As the amount of grain fed is increased, there is a more significant effect on mineral ratios in the total diet. Although they're never completely corrected to ideal, at the high levels of feeding (10 lbs./day), the Ca:P (calcium to phosphorus ratio) and Cu:Z (copper to zinc ratio) are considerably improved. Once again, though, we're only talking about the minerals listed on the bag. Most hays have generous, if not excessive, amounts of iron and manganese, borderline-to-low magnesium, and you have no way of knowing if the levels of those minerals in the feed are improving the situation, having no impact, or even making it worse.
Smart Feeding
- Grazing a pasture with a variety of plants/grasses or feeding a variety of hay types usually helps to minimize mineral imbalances in this important part of the diet.
"One-A-Day" Equine Formulas
Taking a supplement that supplies all or part of daily mineral/vitamin requirements is much more likely to be beneficial for a human than a horse. The reason for this is simple: variety. We would never eat precisely the same meal, three times a day, 365 days a year. However, the number of horses with access to a variety of different plants and grasses to eat is rapidly shrinking. Many horses eat precisely the same grain and hay for months, even years, on end. This is especially important with minerals.
The horse can guard against over-absorption of minerals to a limited extent by shutting down absorption pathways in the body that actively seek and bind minerals, pulling them into the intestinal cells. However, minerals are also absorbed in the spaces between cells and this process is not regulated.
Consider free minerals inside the intestine as balls in a lottery machine. If you have 10 black balls (mineral X) for every 1 white ball (mineral Y), it's easy to predict which color has the best chance of hitting the chute. This is one reason why mineral ratios are important. High concentrations of minerals that can bind to other minerals and prevent them from being absorbed will also take a greater toll on minerals that are in short supply to begin with. Putting a one-a-day into an imbalanced "soup" in the intestines doesn't correct the basic problem.
What's It Mean?
What's the real-life significance of this? Obviously few horses have their diets meticulously balanced, but they're doing just fine anyway-or are they? But consider this: If all those supplemented grains and one-formula-fits-all supplements, designed along the "One-A-Day" lines, were really getting the job done, there wouldn't be such a huge market for hoof supplements or skin/coat supplements.
Throwing an excess of minerals at the horse is not without its problems either. Enteroliths, urinary tract stones/gravel and performance-related problems such as thumps and tying-up may all have their roots in mineral excesses.
When fed at 10 lbs./day with 22 lbs. of hay, our "average" premium-supplemented grain was able to improve even the skewed mineral ratios for Ca:P and Cu:Z in alfalfa hay, but the diet ended up providing 825% of maintenance and 550% of moderate work requirements for calcium.
Horses with access to pastures containing a mix of grasses, or mixed grass hays, and up to 20% legumes (clover, alfalfa) are much more likely to do well with supplemented grains or set formula mineral supplements because their base diet has a better chance of being inherently fairly well-balanced. Some people are even fortunate enough to have access to a single type of hay that happens to have a favorable mineral profile.
However, if you find yourself faced with one or more problems that likely have a component of mineral deficiency or imbalance, it makes more sense to us to find out exactly what the problems in your horse's base diet are (using hay analysis or regional analysis figures for your area) and supplementing only what's needed in the correct amounts.
Bottom Line
Supplemented grains can help get the required minerals into your horse, but to have a significant effect on imbalances they have to be fed in high amounts, which can lead to excessive intakes of some minerals and may not always get the job done properly.
If you are relying on a supplemented grain, request a complete analysis, including all minerals, from the manufacturer and compare this to your hay's (or region's) requirements. If the feed manufacturer will not release this information to you, find one that will.
