Originally Posted by Ryle
And just to clarify, even though ivermectin is currently effective and so can be used as the main drug in a deworming program we still need to limit it's use to only when necessary. This is because frequent use leads to increased risk of the parasites developing a resistance to it. And this is already starting----a study done in KY last year showed that strongyles on one farm were resistant to ivermectin.
The AAEP site does not say rotating is not necessary.It says "To date, ivermectin resistance has not been noted for any of the major parasite in adult horses, so rotating may not actually be necessary"
MAY is an important word. The information is also from 2007. Several studies and advances since then.