Broomd
WKR
Yes, wife uses the microscope to examine.Right, but do you do fecal floats?
We lost all effectiveness with it 20 years ago.
Parasites build up resistance.
So far, so good as far as resistance. We don't use it just because the calendar says it's time. We use it when we suspect conditions warrant it.
And frankly we use a far less volatile 'mectin,' one which isn't subject to long term meat and/or milk restrictions.