How Effective Are Grazing Muzzles in Reducing Pasture Intake?

Limiting pasture intake is recommended for obese horses and ponies, especially those at risk for laminitis.  This can be difficult to do if horses have access to pasture full-time or when, for example, stabling is not an option.  Using grazing muzzles has been recommended but how much of an effect do grazing muzzles really have on reducing pasture intake in horses? 

 Read more about this research and the results here:

 Grazing Muzzles Ponies March 2016