Pilgrim Goose paralysis

[FamilyJuulsFarm]

My gander, Ryan Gosling, has been getting progressively worse.
He was previously the boss in a flock of 11 girls and 3 other boys. About 6 weeks ago, my husband first noticed that he fell over continuously when he tried to herd him out of part of the garden.
Since then,I have switched to a higher quality feed, wormed everyone, and started vitamin supplements. However, Ryan has got progressively worse. He has become thin, spends a lot of time sitting, and looks pale around his eyes. I noticed yesterday that he had quite a heavy lice infestation so I dusted him with pestene. All lice appear to be dead today.... but he isn't walking at all. His voice is faint compared to normal. Still eating seed mix, still drinking, faeces looks normal...perhaps with a little more of the white part compared to his flock. He's not being picked on. The rest of my birds look healthy enough, though one goose has had dropped wrists since she went broody in December. I'm not sure why this has happened either.

My flock consists of 15 geese, 12 muscovies and 9 chickens. They are locked in a 100m2 pen overnight but free range during the day. There is shelter but the geese elect to stay out, no matter the weather.

So to summarise:What can I do? can anyone suggest what he may be suffering from? He's been treated for parasites, should I administer an antibiotic? What one? How much?

 

[Pyxis]

It's good that you're worming just in case. All it would do if it wasn't the cause of this is kill parasites that may be putting extra strain on him.

What are you feeding? In your post you said a seed mix, but that's not what poultry should be eating. Is that just a treat and do you also feed regular feed? How much niacin is in the feed? Geese need higher niacin in their feed than, say, chickens do.

Have you checked for bumbefoot?

Is he having any respiratory distress?

 

[FamilyJuulsFarm]

The seed mix is a poultry formula by Red Hen and he has access to green grass all day long. Majority of his diet is grass. The other geese in the flock are quite fat. He doesn't have bumble foot or respiratory distress, though his voice is a bit weak.
Point taken about niacin, I'll add some brewers yeast to his diet.

 

[FamilyJuulsFarm]

A follow up -

After 5 days on the ground, I really thought I was going to have to make a difficult decision.
But he is up and walking!
I credit treatment with sulfonamide antibiotic for his recovery. I don't know what the problem was.... but it has worked.