when it doesn't work and has the opposite effect, the results can be truly devastating. Ie....IR, laminitis, crazy neurotic behavior, hormone level issues, obesity, poor hoof condition, udder development, and what other so far undocumented but likely effects like thyroid trouble (well documented by soy in people and other animals), reproductive problems, etc... (too many to list like increased risk of cancer, etc...)
Again, Equilibrium had TB's with issues on the same RB I used. It might be fewer TB's as compared to easy keeping breeds but again, why risk it?
ALL of my horses returned to normal after having the RB removed from their diet and remain looking fantastic in weight, bloom and overall health.