A bit late to help, but this sounds like a case of ivermectin overdose. I've seen it in a dog. Stares at the wall a lot, won't eat much. Almost acts normal. A little bit gets past the blood brain barrier in vertebrates, but wears off eventually. Invertebrates have no blood brain barrier, so...
According to this, a chicken might drink 0.5 to 1 liter of water a day:
https://www.backyardchickencoops.com.au/blogs/learning-centre/how-much-water-does-an-adult-hen-drink-per-day
Hmm, that seems like a lot of water. Are we really sure that they drink that much? If they drank half a liter of...
Disclaimer: Many of my claims are speculative and not all of it is based on personal experience or research. Nothing I say is guaranteed to work or be correct. Do whatever you want.
This is what I've read elsewhere, 4mL per 1 gallon of the 1% injectable solution, but unsure of the...
