At the vets we worked out 80% hay, 15% fresh veg & forage, 5% pellets.
So unlimited hay, around a handful or two of veg (keep fruit as a treat once a week), then around 15g to 20g of pellets.
This is per rabbit, per day.
Generally they'll eat everything you offer unless they're I'll or don't like the taste. The main thing is ensuring they eat enough hay.
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