Your chicken has Scaly Leg Mite.
Some chickens have a genetic predisposition for it.
Most treatments rely on suffocting the mites. Don't bother with DE for this, or anything else come to that.
There are plenty of options to deal with the problem.
The fastest and, depending on the chickens temprement, is to dip the legs in surgical spirit (rubbing alcohol). The legs nee to be submerged for a minute or so.
I've used Vasaline mixed with Betadine (75% to 25%) in the past. The Betadine is anti fungal and antiseptic which helps to clean up the mite shite and prevent infection.
What you do need to be aware of is a single treatment isn't going to cure the problem, maily because the mites lay eggs under the scales and these hatch and the cycle starts again.
Whichever method you decide to use, you will need to repeat the treatment, first 5 days later, then once a week for a couple of weeks.
Do be aware that the scales will not go back to their normal orientation; the chicken has to shed the lifted damaged scales and this can take some months. The legs will only look normal again once new scales have grown in.
I've recently started using this product for SLM. I don't know yet how effective it is but I'm told by people who have tried it that it works well. It can be applied as a preventative/leg maintainance on a weekly basis.
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