Pelleted feed is often made from alfalfa hay. The pellitizing process involves heating the hay which completely destroys all seed viability. For all its size, the average 1,000 lb horse has a relatively delicate digestive system, completely different from that of ruminants such as cows, sheep or deer. A too-high protein level can upset its delicate metabolic process to the point of endangerment and even death. Switching from bulk hay to pellets suddenly can cause colic.
Pellets can also cause horses to choke.
This option could potentially be hazardous to horses through spread of disease if they had to be quarantined at trailheads. The California program of certified weed-free forage was supposed to be implemented by the year 2003. But it has encountered a number of obstacles at this writing. There is no funding available to implement it. Agriculture commissioners have no CWFF coordinators.