I've just read that an average 2.5kg bun should be having between 1 1/2 and 2 1/2 cups of fresh veg a day. theres a link on another post of what they can have as well
Mine get this much every morning between 4 of them
rabbit.org said:What quantities of food should I feed mature adults? (1 to 5 years)
Unlimited timothy, grass hay, oat hay, straw
1/4 to 1/2 cup pellets per 6 lbs. body weight (depending on metabolism and/or proportionate to veggies)
Minimum 2 cups chopped vegetables per 6 lbs. body weight
fruit daily ration no more than 2 oz. (2 TBL) per 6 lbs. body weight.