How many times have you heard this' ”I give my horse at least some grain so she’ll get her vitamins and minerals.”
Used correctly, supplemented grain mixes can help with vitamins and minerals, but the major source of both is still hay and pasture.
When fed at the recommended feeding level, grains typically provide from 50 to 100% of daily minimum requirements for the nutrients on the label. However, they can’t correct hay mineral imbalances and only provide that level of minerals if you feed the full daily amount.
To keep the horse from getting fat, you’d have to cut hay at a rate of 2.5 to 3 pounds for every pound of grain. Therefore, if you go from giving no grain to feeding 5 pounds of grain (the usual recommended rate), you’ll have to feed 12.5 to 15 pounds less of his hay (not good!).
If you cut the grain back to a pound a day, you’re only giving 1/5 of the minerals and vitamins so instead of 50 to 100% of requirements, it’s now 10 to 20%. If all you need to do is up the horse’s vitamin/mineral intake, choose a supplement instead.