I use it at least once a year in my rotation and it has worked fine.

The original complaints when it first came out about horses dying from it was spurred by using it on horses that were heavily infested and had a huge kill off.  All the dead worms overloading the horse system.

I have 4 tubes sitting on my desk now that I plan to use March 1st.

We have used it with no ill effects.  I would use a weight measure tape to get an idea of your horses weight so you don't overdose.  Some folks I know just shoot the horse a whole tube regardless of age or weight.  Not a good practice in my opinion.

Wormers are a LOT cheaper in the catalogs.  Especially if you buy in bulk (6 or more).  We buy many products from Valley Vet and Country Supply.  They both have websites where you can order online or request a catalog.

RIDE ON!

I have seen people do exactly what Dwight describes, shooting the whole tube regardless of size.  These newer drugs and formulations work as advertised only when used correctly.  If you are unsure about the weight of your horse ask your vet or take them to get them weighed.

Any wormer can kill a heavily infested animal.  When I bought my first show horse, I took him for the vet check and when he passed we wormed him and took him back to the barn.  Thank God the local equine vet owned the barn I used while mine was being completed.  We received a call that next morning that my newly purchased horse nearly died during the night and the vet slept with him keeping him on IV for electrolytes.  Poor kiddo, his belly was full of worms and he laid down in his stall with his bowels just gushing liquid all night.  They cleaned him up the next morning and when I got there he looked like a bag of bones!  This was when I realized that not everyone cared for animals like they should, a hard lesson for a young person.

As with any drug use as directed!

Thanks for the input, all of my horses have been on a regular worming shedule for years so I am not concerned about an overload of dead worms in their system.  I have 3 adult horses and one yearling.  One of the adults is a pregnant mare and I was not planning on using it on her or on the yearling, just the other two.  I will check their weight too as a precaution.

Again.... appreciate the helpful feedback.

We have used Quest since it first came on the market, no problems whatsoever. Used on our babies, to my 26 yr old barrel horse. Never had a problem with worms yet. Like others have said, do a little research. Contact a Vet Teaching College (Ames, Iowa has one) see what they think. Don't buy the really cheap stuff instead.. Just remember to use  a weight tape, you'd be surprised what you THINK your horses weigh, and what the difference is with a tape .

I've been using it for years with no problems what so ever.  I use it as part of a rotation worming schedule.