Vinegar can interfere with calcium uptake, especially in hot weather.
My birds are confined with no great deep shade for last half of the day so I have to be vigilant during heat waves. I do have shade cloths up on run, which helps, but still not deep shade.
To help cool down the coop I also have a box fan in the east window of coop, where it's shady most the day, and turn it on late afternoon...blows cooler air into coop and pushes hot air out.
To determine heat stress levels I go by activity level, if panting and wing holding seems extreme, I throw out a few treats to see if everyone is moving well.
Deep all day shade is best but....I don't have much of that.
This has worked very well to keep heat stress/stroke at bay:
I give a dose of
Sav-a-Chick electrolytes/vitamins about once a week during heat waves.
It
really seems to help....started this after they saved a heat stroked hen once.
Can mix up a smaller amount, just wrap the packet tight and store in a dry cool place.
Always have plain water available too.
BIG(9x14x2") chunks of ice last all day for wading, sitting, and sipping.
Much more useful to the chickens than frozen foods and treats.
Make space in your freezer!