What is the forage to concentrate ratio for a broodmare in the 10th month of gestation?

There is no "forage to concentrate ratio" that must be adhered to. The basic rules of equine nutrition apply with the exception that there are certain nutrients that should be fed in higher quantities. All horses should be fed 1.5%-3% of their body weight in forage per day as necessary to maintain weight and energy levels. Horses do not require concentrate feed in general though for certain situations concentrates may be fed to provide increased energy for performance or breeding. The amount of concentrates in the diet should be kept to a minimum as increase in concentrate feeding is linked to an increase in the risk of colic. For pregnant mares who need supplemental nutrition for breeding or to compensate for less than good forage quality they should be fed a concentrate that is labelled for use in pregnant or lactating mares at a rate according to the label. This amount can vary quite a bit depending on the type and brand of concentrate feed being offered.