<Anything I put on her foot/frog will just be washed away with the wet, muddy ground so maybe some one can give me some suggestions.>. 

I have found the Red Horse products (Hoof Stuff, Artimud, Field Paste) stay on relatively well in wet conditions. I clean the feet, then put each foot down on a dry towel (on top of a yoga mat or something similar) for a few minutes before applying. These products are made in England, where they know about mud! As you know, it can take months to improve if not resolve thrush, and the zinc-based clays like the Red Horse products are gentle enough to use long-term. 

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Maxine and Indy (PPID) and Dangles (PPID)

Canberra, Australia 2010
ECIR Primary Response

https://ecir.groups.io/g/CaseHistory/files/Maxine%20and%20Indy%20and%20Dangles 
https://ecir.groups.io/g/CaseHistory/album?id=933