Sparingly, calcium content is fairly high and greens contain a lot of moisture.
Also unless you know what has been done to the plants spraying wise and access to the field for dogs, cats, wildlife that can spread internal parasites, i'd be cautious.
For my rabbits i prefer to harvest above the 1m off the ground line or my own garden. Means they mostly eat thin branches with leaves on. Leaves are more nutrient dense and the branches themselves give them something to chew that keeps their front teeth worn as they need to be and the whole chewing function of teeth and molars working correctly.
Even animals with a sensitive digestion like rabbits can handle a fair bit with consistency and an always there baseline to the diet. Hay is a good one for that, because it stores easy and is dry, most free supplemental foods are fresh greens that may be to wet on their own to provide enough fibre to keep everything moving towards the exit. Mine here do fine with 20%-50% greens in the form of branches, bamboo, herbs. Now i don't worry much about variety because and they can handle what i give them safely in these amounts and my base feed is a pellet for the minerals and such along with 2 types of haycob (like a big pellet) that has multiple species of gras and herbs in it.
If i couldn't buy the pellet and hay i'd be way more picky about what to feed, gather way more variety per day and try to harvest and store more for winter. Part in the form of treehay most likely because that doesn't require machinery, just some big loppers/pruning shears and a drying rack.
