I would start by treating for parasites, lice and mites. Ivermectin pour on, or added to water. If you can, you give him a dust bath yourself if he wont. Electrolytes and vitamins (with A, D, E, B, Selenium), peas, cat food (vet recommended to me for sick chickens), scrambled eggs daily.
If...
Long story short -> I have an indoor Rooster (Chicken Little), aged 1.5 years. Never around the outside chickens. He gets normal chicken feed, scrambled eggs, peas, meat, bread, lettuce, tomatoes, carrots, a wide variety of healthy foods for chickens. His comb and wattles are perfect, and always...
So I have a 3 week old embden gosling, and a 5 day old Chinese gosling. They're super healthy, spoiled, happy baby geese. But I have just noticed the other night while they sleep, one of them loudly whistles while she sleeps! Is this a normal goose thing? Or just something my goose does? Or...
I have a 9 day old gosling who I take out to graze, or on cold days I bring the grass to her. But I leave some grit for her as well or she finds it herself outside and she is doing great, growing fast. Absolutely loving her greens.