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Looks like her feet are pointed inwards (Pigeon-Toed) which is a common sign of a B3 Niacin deficiency. I would start her on Cattle B Complex Injectable, Durvet brand immediately, you can give her 1ml a day orally with a syringe or over treats, water is not a preferred method of administration since they waste so much water, it's hard to calculate the dosage. In conjunction with this, if you arent already, I would start feeding her a feed formulated for ducks or all poultry, as plain chicken feed does not contain enough niacin for ducks, which leads to problems like this. If you have other ducks, I would start them on the B complex too, even if they are showing symptoms. I would like to see a video of her walking too, just to be sure, although giving the B complex won't hurt any.
This is the brand you want.
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