I used to use the whey to make the layers mash

Even your hens ate healthy back in the day 🙂
Fascinating process and you obviously are expert at making kefir. I remember when I lived in California it was difficult to get raw milk. There was a health food store near us where people gathered early in the morning and a truck would pull up selling raw milk out of the back 🙄 you would think they were buying illicit drugs or something