Fly predators are tiny insects that feed on either the flies or the larvae, killing them. You turn them loose when the weather/climate is right for flies to be present and they know what to do.
For the simplifly to work it would need to be used on all horses in that location and it does not prevent others from coming in but it will reduce the numbers significantly of what would have been there had a feed through larvacide not been used.
Feeds should be fed by weight not volume so if you have a way to weigh your feed or let us know the size scoop you are using it would help.
I would ask who decided on the schedule and feeds they are currently on? Are they boarded or at home? Are your parents experienced or other adults in your family? If the mare isn't holding weight while in work on what she is currently at something needs to be adjusted or added. Knowing whether they are stalled or have access to pasture or free feed hay and how much time they have on the pasture or hay could make a difference in what is suggested.
You say the older mare shows twice a month. Are you the only rider? How much and what level of activity is she ridden? For the younger - what type of work or activity level?
Some horse people change their horse, they change their tack and discipline, they change their instructor; they never change themselves.
Last edited by QtrBel; 02-06-2020 at 02:07 PM.