My vote - let them
drink. Picking up a bug at a ride is the last thing I worry about.
That's a risk you take every time you take your horse off it's own property
& mingle it with other horses.
FYI Heidi - When
you ask a Quarter Horse to do something, it doesn't say "sure" it says " Make me
if you can!" All 3 of my QH are more stubborn than a team of
mules!