I think we are probably all on the same page regarding herbicides and pesticides. I will suggest that the odds of a single dose for a period of a week or two of ivermectin in deer feed is unlikely to have any impact on dung beetles or anything else. But if that is a concern, another thing we do is add essential oils to our deer feed including a garlic extract, clove oil, and a couple others...frankly I forget all...cinnamin maybe? Nonetheless these essential oils act as a natural anti biotic improving gut flora and reducing parasitic load. Just another of the small details that when added together can have big results
I have also read that chicory can have a cleansing effect for deer.