What to feed growing foals- Part 3-the minerals.

Are my foals getting enough minerals in their diets?

What of these new studies that say that foals and broodmare can really benefit from more Copper?

Are my animals getting enough to ensure they have a long sound life ahead of them?

Like any breeder and foal raiser, I ask myself those questions pretty regularly. We want the best start in life for our foals and I find myself pretty bewildered at the wide array of feed and supplements out there being offered and touted as the best solution to this niggling worry. But when I go looking for actual data on what foals actually need I am faced with a couple of challenges.

  1. The information in other blogs and articles are so vague that it is of no use. “Make sure the foal has access to quality feed.” Please define quality? “Feed it a foal ration and follow the feeding instructions”-How is this feeding requirement the same for all foals raised everywhere?
  2. When looking into nutrient requirements- when I can find them from unbiased sources materials- the units are sometimes hard to follow, inconsistent, and are all over the place: mg/kg, ppm, %, gr/BW, kg, and lbs of course…
  3. Finally, when the numbers have been worked out for you they always mention that this is for an animal with a mature weight of 1100lbs- seems to be the gold standard probably because its the average weight of a QH and let’s face it there are way more of them in North America then warmbloods or sport horses. Average sport horses and warmbloods are 1250 to 1400 lbs at maturity and face the challenges of growing for longer with their livelihood literally depending on the quality of their constitution.

So, for those reasons, I went on the hunt to recalculate and do a sanity check on what sport horses and warmblood foals need

The key minerals.

Looking at minerals there are a few that require our attention. All minerals and vitamins are important of course but some have been proven to directly related to the future soundness of the animals we raise and so we focus closely on these. Calcium and Phosphorus (vital building blocks of bones) as well as Copper and Zinc.

Calcium and Phosphorus

Those two are pretty straight forward. They are well researched and the requirement for mature horses, broodmares, and growing foals is fairly well understood. The Calcium and Phosphorus contents are clearly written on almost all commercial feed and ration balancers and are often the bases for which feeding recommendations are built.

Let’s take a look at the requirement of various type of horses:

From: Storey’s Guide to Feeding Horses, 2003

As you can see the requirement of the growing weanling is well above and beyond any other class of horses. By a lot! Much higher than lactating mares too, that seems odd, doesn’t it?

Well, it turns out that there is not that much Calcium and Phosphorus in mare’s milk after all.

So why do growing weanling requires so much more than is available in their mother’s milk- doesn’t Nature provide at least some semblance of what is needed?

I think it comes down to understanding that those requirements are for optimal growth, horses in the wild stay small and grow slowly for a good reason. They are also not required to perform at the level we expect our future athletes to do so.

Since we are not raising mustangs that will live out their lives out on the range we must accept that we have a responsibility to provide a bit more.

What does that mean for our growing foals?

Again I propose ranges of values because every foal is a bit different in weight (here in lbs) and growth rate etc…

Range of requirement based on a range of size


They are always discussed in combination with each other as the ratio of Calcium to Phosphorus was identified as being an important aspect. The Calcium and Phosphorus content of any feed is found on the label and expressed most commonly as a %. Therefore it is not difficult to calculate.

But you must then consider how much are they getting from their mother’s milk (hint it is less than you think) and from the forage they have access to.

Here again, the choice of forage will have an impact on how much,  if any,  you need to supplement. Alfalfa provides a lot of Calcium compare to other types of hays. If you feed mostly alfalfa you are probably getting enough Calcium in their diet but Phosphorus is probably low.

If I look a the hay mixture we have on hand; grass hay with 25% alfalfa I see that from the analysis my foals need a little bit of supplementation.


However the calcium and phosphorus content varies quite a bit depending on the type of forage (legumes like alfalfa have more calcium 1-1.5% then grass hay 0.2-0.3%) so it’s important to base your need for supplementation on how much calcium and phosphorus are in the forage you have available.

Copper and Zinc

These metals are linked to the optimal development of cartilage and are of premier importance when considering the requirement of young sport horses. Studies have shown that broodmares need to be adequately supplemented in Copper and Zinc in order to reduce the incidence of developmental orthopedic disease (DOD) in their offsprings. However, it is also strongly recommended that the growing foal also be supplemented at rates much higher than those adequate for an idle mature horse.

Here are the requirements for the growing foals, once more given as ranges. There is not much point fussing over decimal point here (as for other numbers presented here) because were are not working with very precise science, and there is the whole debate of the form of copper (chelated etc.) best absorbed by horses. Using the recommended feeding rate of the National Research Council (NRC) here is the range of value needed (again with weight of the foal in lbs). So these should be seen as a minimum when we consider that most commercial feed will have the less bioavailable form of Copper because of cost reasons.

Contrary to Calcium and Phosphorus however the Copper and Zinc content in hay do not vary much and are generally quite low. The concentration of Copper is between 4 and 10 ppm in forage and that is generally enough for idle mature horses but for growing horses, there is simply not enough in conventional forage and grasses to reach the amount required.

Alberta forages (grass and hay) are very low in copper (4ppm) and so like everyone else we must rely on supplementation to reach the desire levels in our weanlings and in our broodmares.

Most hay analyses do not include the Copper or Zinc content, it is however safe to assume they are quite low and supplement accordingly unless you live close to an active smelter in which case the ground being enriched in metals from emissions could yield forage with higher values.

The value of adding copper and zinc to the diet of growing foals was identified for many years and therefore the feeding requirements were increased significantly 0ver what they are for mature horses. (10 ppm for mature horses and 50 ppm for growing horses). When looking at most commercial ration for foals, most feeds meet those requirements if fed at the full recommended rate. Like we saw in our previous article that might mean feeding an excess of protein, however. It might be better to look at some mineral supplements that contain no excess protein. It will once more depend on the type of hay your feed.

But overall the commercial feed, when fed at the recommended rate meets the requirement for Calcium, Phosphorus, Copper, and Zinc.

The same cannot be said for pregnant mares, the broodmare feeds are often not particularly fortified in copper. According to the study done in New Zealand with control groups, to prevent DOD and physitis in their foal, 1200 to 1400 lbs broodmares should be fed between 600-700 mg of copper. Assuming they get between 100 and 150 mg of copper from the forage they eat they need to need to be supplemented in the range of 500 to 550 mg/day.  Clearly, some concentrated mineral is the way to go, unless you want to feed your mare large quantities of ration. The highest Copper content I could find in ration available in Alberta is the ProFrom Step 7b mineral supplement ( with 890mg/kg of copper) but it’s meant to be fed in small quantities.

Supplemental sources of copper are recommended particularly for horses in Western Canada that are destined for athletic careers.

The best is to work with an accredited nutritionist to determine the best diet for your animal based on the forage that is available to them-commercial feed can only get you part of the way.












Owner and worrier in chief at Formosus Sporthorses in Alberta she's been breeding horses for over 15 years. Warmblood, warmblood crosses, and a few saddlebreds. She loves handling mare and foals and is passionate about giving foals the best start possible.

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  1. […] info here: Source of Nutrient, Minerals and, […]


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