The MFD of these units would probably be less than a few hundred Gauss. The distance from the magnet affects the strength. An inch away from the pad would greatly reduce it's magnetic field. This would render magnetic blanket claims of deep muscle benefits somewhat suspect. This would require magnetic fields hundreds of times the strength generated by these devices and could only affect a few drops of blood for a brief instant.
Horses have a very large volume of blood.
According to leading educators in physical chemistry, it would be impossible for such magnetic forces being used in the leg, foot, and blanket devices to impose the hall effect on any substance. It is common practice for a sales pitch to single out one tiny scientific morsel which would make their product look good but totally ignore the overall picture. In effect, since this magnet purportedly lasts forever, there is no expending of energy. For any process, such as the separation of charged ion particles, to take place, it must either be spontaneous, like a chemical reaction, or work must be applied. Since it is obvious that no work is being applied here, we are seeing the elusive perpetual motion machine.