I've found that chickens will try anything that is "bite-size". If they can swallow it, down it goes. With big stuff, like a squash or a watermelon rind, they peck at it trying to pull off bite size pieces to swallow, and with smaller stuff that is more than a bite, they will try to shake it into smaller pieces. So if I want to try something new on my chickens, I make sure to cut it to an appropriate size.
There lots of ways to do this. If it's in the
yard and I can run over it with the lawn mower, the pieces in the bag are usually the right size. Any time that I empty the lawn mower bag and move the chicken
tractor over it, they think they've gone to heaven. It's good for a couple hours of scratching entertainment.
Right now, I am experimenting with giving them fermented foods. I came across some articles saying that Lactobacillus in the diet can increase egg production, so I thought I would try it out. So I'm chopping vegetables and soaking them in brine and the chickens seem to like it so far.