oxalates were not mentioned so i wanted to point out that: potatoes, spinach, rhubarb and almonds contain the highest amounts of oxalates which bind with free calcium to create calcium oxalate crystals and stones and robs the body of available calcium for egg shell production (in chickens) and strong bones (in humans).
so if you do feed your chickens spinach maybe give some strained yoghurt at the same time. this will allow the oxalates in the spinach to combine with the calcium in the yoghurt, instead of sucking it out of the body, and will then be excreted.
straining the yoghurt removes the whey which contains the majority of the lactose. i chill it in the fridge while straining then give it on hot summer days. they love, love, love it.