I cut off any moldy spots, but if I find some corn worms or cabbage worms...I just leave them. That's extra protein! I chop the whole bunch of veggies up and add in any weekly leftovers, stale bread etc. The chickens and Guineas love it and as I've said before: the more free feed I can give them, the more the feed bill goes down.
I think of it this way, If I save seeds this year then my expense for the plant is $0. To plant them in the ground may take a few minutes but it doesn't cost me any money. I fertilize with chicken poop tea which takes a few minutes each time, but it's free also. I water with duct pond water. Also free (and needs replaced regularly anyway) Each plant produces upwards of 3lbs of veggies, depending on the plant of course. I would guess tomatoes and cucumbers to be closer to 6lbs each. That's a lot of free feed! Plus I'm adding lots of vitamins and nutrients to their diets. Produce laying in the run attracts bugs which the chickens eat which means more protein in their diet also. A varied diet makes for happier chickens and brighter egg yolks. Plus it's an easy way to make a dent in the food bill.