This is the dosage listed for the product on Jeffers Pet website
“For rapid results, give undiluted, directly into mouth. 1 cc per 3 lb. Can be measured in the bloodstream in minutes.”
https://www.jefferspet.com/products/poultry-nutri-drench-8482-4-oz
https://jeffers.cvpservice.com/product/basic/view/1581002
There isn’t information that I can find for duration so the best I can suggest is what I’ve done in the past. I’d give it once in the morning and once in the evening for maybe two or three days, and then lay off because I worry about overdosing on Vitamins A and E. The body doesn’t really store vitamin C or B very well so it’s really difficult to overdose on them but A and E are a different story.
The most important thing to keep in mind is that I am not a vet, I’m just someone else who’s doing the best they can with limited means so it’s always important to do your own research on everything and make your own decisions based on what you find.