We have a baby bunny, around 400 grams (1 pound or so). He has a bed of hay and pellets in the cage and we feed him greens in the morning and evening. However, it seems that no matter how much parsil or lettuce we give him (e.g. 2-3 handfuls), he is still hungry. He keeps following me around and lick my feet until I give him more. Eventually, when I think he is full, he starts exploring, running and jumping around. So how much greens should he eat without overfeeding him? Thank you
What you are experiencing is that your bunny just really, really likes his greens. Lettuce is especially palatable for many bunnies.
About 1 cup of greens per 1-2 pounds of weight is usually the recommended minimum amount. Some sources say 1 cup per pound, some say 1 per 2 pounds, I fed my rabbit on about 1 cup per 2 pounds, plus a small amount of other veggies like carrots, apples, pear, cabbage, etc, and she did well. Note that while you can overfeed fruits and vegetables easily, rabbits can safely eat almost an unlimited amount of grass hay (timothy, orchard, or other grasses). You should also limit so-called 'high oxalic' greens like parsley and spinach, but you can give your bunny more than recommended minimum of low oxalic acid greens if desired.
Some rabbit owners allow young bunnies under six months to have unlimited pellets as well, but it doesn't seem like there's wide agreement on if this is a good idea or not. Adult rabbits should not be free-fed pellets in most cases.
Here is more detail about feeding your rabbit greens and vegetables: https://rabbit.org/suggested-vegetables-and-fruits-for-a-rabbit-diet/
In general rabbits use to eat a lot of little meals over day and night. They are "adjusted" to this style, so it is beneficial for them, if they can do so in your home too. If they can choose their food free from an overwhelming offer, they will not "eat until burst". They would choose themselves the appropriate amount of each food.
We as pet owner have problems to give them this "land of milk and honey" because we can not guess exactly right, what nutrients the rabbit needs exactly today.
But we can try...
There are some basic foods, which you can not feed "to much", because your rabbit (if it is accustomed to this sort of food) can choose themselves the right amount. Hay is one of this, grass and dandelion one another. But with fresh green food you have to start slow, with little amounts and increasing every day. For example if the food goes with the seasons, or your rabbit starts after a special diet for health reasons new with fresh food.
How to get this fresh food strongly depends on where you life. In European area, you can for example feed almost all leafs of native trees, or just cut a newspaper page big part of a wild meadow and feed this. After an period you have to take the food outside the cage again, this are the herbs your rabbit do not like (because of taste or health reasons).
If the rabbit became two times a measured amount of food, this will work too. But the rabbit eat all at once, because it is hungry from the last (for the rabbit long ago) meal. It will show this behavior for a small time after you start to feed "more than needed" anyway, but then eat more and more little meals instead of one large.
For my circumstances this way to feed is a good one. I like to take my time outside and every time have a little bag with me, to collect herbs and leafs everywhere I go. Benefit two: I pay only for food, if I have no time outside, or in winter season, if no green grows outside here.
One interesting thing I learned as I get my rabbits is that they can learn what to eat themselves: they can learn from older rabbits and they can try new food with a little bite, observe their own health in the time after it, and then remember this new food as "good" or "ick"! (Because of this "try bite" your rabbit seams to refuse new food first time, and next time it may love it. So a second attempt with it is a good idea.)
So I saw my old female rabbit eating ivy in my garden. Full of sorrow I searched resources, if it is toxic for rabbits, and learned: big amounts can be toxic, but in small dose it help with rheumatic issues (which I know she has). Same thing with my other female: She once eats thuja and I found it helps against a chill... So I trust them to choose (if they have variety) what they need.