this post by Hugo Straker advising caution in the repeated use of medicated grit.
I am far from being a grouse expert, but I am surprised by the response I get during advisory visits about worm burdens in grouse and the gritting policy. I often get the reply that worm burdens are not being assessed and that medicated grit is being used as a prophylactic measure.
There are two issues here: the cost and the build up of resistance to the dugs in medicated grit. I understand the need to reduce every risk it is possible to manage, but I would have thought a modest expenditure in blood testing would show whether the high cost of medicated grit would be justified. However, the risk of the build of resistance to worm treatment offered by medicated grit is by far the most important issue. Medicated grit has been shown to be a fantastic tool, but its use needs to be targeted; it should not just be used as a precautionary measure, however tempting.