Question
I breed Criollo horses in Uruguay. Normally, our horses are raised in open meadows without supplemental feeding, though I am beginning to understand the importance of additional vitamins and minerals. I am afraid, though, that I might exceed what the horses need by feeding a concentrate in addition to the meadow grass. I am especially worried about the foals, as I would like to see them grow and develop as well as possible.
Answer
There are two options for balancing the nutrition provided in the pasture grasses for your young growing Criollos: (1) have the grass analyzed for the nutrient composition and try to find a supplement that complements the nutrients that are low in your grasses; or (2) use general analyses for the grass types found in the pasture to establish what nutrients may be deficient or out of balance, and then pick a supplement made to complement the average forages.
The first method is by far the most accurate but requires more legwork and expense. Also, you will have to find a lab in Uruguay (or Brazil or Argentina) that has the capability to do forage analysis. The specific nutrients that would be of interest in helping you balance the diet of the foals would be energy, protein, calcium, phosphorus, magnesium, zinc, copper, manganese, and if possible, selenium. The other nutrients are usually in good supply in fresh forages, except for salt. The energy and protein content may vary with the seasons, but the minerals generally remain fairly constant over time. If you are truly sincere in trying to balance the diet, it is important to know which nutrients would be of concern if they are low in quantity or out of balance with other nutrients. Out of balance nutrients can be very detrimental. For example, even if there is adequate calcium, if phosphorus is higher than calcium it can cause secondary nutritional hyperparathyroidism (also known as big head disease).
Once you know what nutrients you need to supplement, then there are options for supplying those nutrients. First, the foals should have access to free-choice salt in the pasture. With free-choice feeding, the foals will normally consume adequate amounts to meet their requirements for sodium and chloride, which are typically universally low in forages, without risk of overconsumption. If you wish to get additional minerals and/or vitamins into the foals, then mixing it with salt is a proven way to effectively get horses to eat them. They have an appetite for salt and will consume the minerals with the salt. When it is offered free-choice, there is no control over how much each foal is getting, but usually the salt will keep them from overeating the mineral mix.
The free-choice salt with added minerals/vitamins can work if the foals are all eating some of the mix, but if you would like to have better control over nutrient intake, then the foals will have to be fed a supplement individually. If the grass is supplying adequate calories (energy) and protein, then only a vitamin and mineral supplement will be necessary. However, if the grass is not adequate in protein, then a “ration balancer” product with protein, vitamins, and minerals would be advisable.
If the forage is not supplying enough energy for the foals to maintain their weight and grow, then a commercial concentrate with some type of energy (usually from grain), protein, and vitamin/mineral fortification would be appropriate. When all of the above mentioned products are fed within their recommended feeding rates, there should be no concern about oversupplying any nutrients. The key is choosing the right product for your situation.
If you decide to have the forage analyzed, you should consult a nutritionist to help you find the right choice of supplementation for your horses.
