You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply. Please be patient. This may take a few minutes.
That's an interesting idea but very difficult to confirm. Each drop of 1% ivermectin contains between 0.5 - 1 mg of ivermectin. I might dose ivermectin as high as 0.6 mg/kg to a pup. A 30 kg pup would then receive 18 mg. Depending upon the number of chickens you treated and how much poop he could have ingested there's a possibility - if not very high - that he could have intoxicated himself with ivermectin. Signs of toxicosis arise within 4-12 hours of exposure and may include depression, disorientation, vocalization, ataxia ("drunken sailor"), tremors, vomiting, anorexia, recumbency, blindness, coma, seizure, and death.
I regret that my state board of veterinary examiners doesn't allow me to speak to customers by phone in this venue but other experts in this category may be able to assist you in this regard. Please let me know if you'd like another expert to do so and I'll opt out of this conversation. Please stay in the conversation if you wish.
You nailed it, Rob. A dietary indiscretion rather than ivermectin toxicity should be considered. I would fast the pup for 12 hours but leave water down unless drinking induces more vomiting at which time you should replace his water with ice cubes for him to lick. There's no reason to alter his diet when you offer him food once again.
I can't set a follow-up in this venue so please return to our conversation - even after rating - with an update at your convenience. You can bookmark this page for ease of return.