Never had an issue but we watered the heck out of the surrounding areas and washed out the gutters. They moved the horses to another stable for several days just to play it safe.

Hank

I have cleaned multiple horse farms. The first one I did I was a little worried, I talked to the owner and he laughed. He said that if I knew about all the chemicals that they used I wouldn't be worried either.
Like my good man Hank said, just dilute everything down before you leave.

I'm roof cleaning a dog kennel in a few weeks. I explained the bleach content and they said, "we clean with bleach ALL the time!" My plan is to 1) keep the animals indoors, and 2) rinse, rinse, rinse the dog runs where much of the mix will drip (no gutters.)

I am also in the practice of flipping over water dishes when cleaning to make sure I don't fill them with mix. Might look around for places where the horses drink.

We've cleaned around horses as well. Created some massive mud puddles and just made sure they were diluted heavily. No issues.