My horse lives in a 400-acre pasture with a herd of 35 horses. Very
little of the pasture is flat. It is rocky in places with lots of hills
and uneven footing. In the summer most of the horses wear fly masks. The
herd has at least one flatout gallop daily, and the fly masks do not appear
to interfere with their ability to negotiate the terrain. In terms of a
safety issue, there is no comparison between leaving a halter on an
unattended horse and leaving a fly mask on. All the fly masks that I have
seen are attached with velcro and easily come off under any kind of
pressure. The problem that we have with fly masks in our pasture is keeping
the fly masks on. Some horses like to pull them off each other.
Shirley Delsart