Anyone manage ducks at scale? Questions inside!

Hey, Permies!
We share a small nine-acre homestead with our 80+ ducks. We have had ducks for about 1.5 years and have had next to no problems. We paddock rotate them so they don't destroy any one area too bad. We seed behind them to continue to build soil ecology and the feed available to them. The birds are kept overnight in holding pen that uses wood mulch as a base and hay inside the Duck Mansion. Our male to female ratio is 1>14

In the last 6 weeks, we have had 3 different ladies come up with foot problems and 2 other ladies simply lay over and die in the middle of the night. The first lady with feet issues we had to cull, she would not respond to any attempted treatment, the leg/foot was completely pulled up to her belly and would not more, almost like rigor mortise had set in. The second we noticed early and isolated her added some fresh herbs and veggies to her normal Non-GMO ration and she healed up. The third now has both legs/feet showing bad signs and we will likely cull her if I don't find an answer in the next day or so.  I am attaching some pictures to help possibly identify the issue.

The weird thing is we have had absolutely zero issues since we started keeping ducks. The only change was a feed change, which we have since switched back. I don't believe a feed change would warrant the two overnight deaths, they had no injuries and no sign of stress. Any suggestions on where to start? Thanks!

We had that issue ourselves, but it ended up being with the individual birds and not going to the rest of the flock. A few died of choking deaths, but that occurs too.

Ducks are strange in that due to what they eat, they do not respond well to antibiotics at all, but like you, we have had mostly good luck with them. We however are not at a scale that you are, nor do we plan to be. We looke into it, however we just don't have a market here for that many ducks.

The sores on the feet look like bumblefoot to me--a bacterial infection (staphylococcus) that gets in through cuts or scrapes on the bottoms of the feet. It's very common--staph bacteria is everywhere! There are topical treatments (both sprays and ointments) that can help a lot. Often, just getting the birds out of any damp environment and standing on nice, dry, smooth ground for a week or so will allow their immune system to clear it up naturally. Occasionally an abscess might form, and then you can lance it, cover it with an anti-bacterial salve like Neosporin, and wrap the foot with gauze and VetWrap. You'll want to keep that animal in a confined, dry space while healing, too, of course. If you need to confine ducks away from access to ponds or tubs of water, keep a close eye on their nostrils, eyes, and uropygial gland (the oil gland on top of their tail, near the base of the spine) for signs of inflammation or irritation. If they are getting irritated or if the gland seems blocked, remove the foot bandage and give them supervised time with a shallow tub of water so they can preen and get their skin and nostrils back to condition. After they've had a bath, dry the foot thoroughly, re-apply the salve, and re-bandage.

Your mention of birds keeling over dead overnight, and birds with stiffness, also has me suspicious of botulinum toxin. This comes from eating something that has spoiled, and has grown clostridium bacteria on the surface. All birds (and humans) are susceptible to it--I've even seen a dog paralyzed from botox poisoning--and yes, it's the same botox some people inject into their faces to prevent wrinkles! But waterfowl, particularly ducks, seem to have extreme susceptibility to botulism poisoning and paralysis. So be sure you're inspecting their food and their enclosures carefully for signs of spoilage. Mid-rotation, walk their enclosures daily and pick up any dead rodents or songbirds you find (a prime source of botulism), any really old fruit that may have fallen off trees, etc.