There are multiple plant species in your picture, but the primary one is crimson clover. That is safe to feed as part of a varied diet.
Off to the right is a sprig of what appears to be horse weed. That one is toxic. Don't let them eat that one.
It looks like a type of clover - but the cover I know here in the UK has a white line across its leaves and rounder flowers in purple or white.
So I'm not 100% sure, but google 'types of clover' to see if you can find a match then check it on www.thetortoisetable.org.uk