The main cause of limping is nutritional deficiencies usually due to an improper diet that doesn’t have enough niacin and other B vitamins. Often it’s because waterfowl are being fed a feed oriented towards chickens and not an all flock, multiflock, or waterfowl diet.
I don’t know what you’re feeding them but if it’s a chick start or grower you need to switch to a flock raiser, waterfowl start or duck start and get the gosling a liquid multivitamin or liquid B complex to give him a boost of what he’s lacking.
If you already have him on that check the tag on the feed, feed older than 4 months loses its potency and won’t be as nutritious.
I don’t see bumblefoot on those feet but some of those dark spots resemble a sort of dermatitis caused by bacteria from walking on damp bedding or mud for too long, often a weak immune system is also to blame. I had a very wet, warm winter this year and one of my ganders who has repeat bouts of intestinal infections got it this winter. The scales will feel rougher or raised and the skin will become somewhat swollen as it progresses. If the dark spots wash off with water, then this probably isn’t the case.
What you do for that is that you fill up a bin with warm water and epson salt and you make him stand in it for 5 to 10 minutes once or twice a day, then apply neosporin to the affected areas after the soak. Repeat until the condition goes away. It’s preferable to bandage the feet or keep them in some sort of booties between soakings to keep the feet as dry as possible.
