Hi and congrats on your new bunny!

The reason why you’re not supposed to give baby rabbits treats, is that their microbial gut flora isn’t fully developped. That means they have sensitive stomachs. Especially sugary food can cause gut upset. Introduction of new food such as fresh greens should be done slowly and gradually and the HRS recommends you start around 12 weeks of age.

That said, because your bun is used to oats since he was a baby, you can use oats as treats for training him and bonding with you. It is not the best rabbit food though, so I personally think you could stop mixing oats with his pellets (or reduce amount of oats gradually) so his main food intake comes from pellets and hay. It’s especially important to get a young bun to eat lots of hay. If he fills up on oats, he will be less inclined to eat hay. Hay is what makes the gut flora robust and diverse, and it also keeps the teeth in good shape.

If you only give oats as treats, they will also be more attractive to him (the value of the treat increases). For training purposes, you want to be able to offer a high value treat.

I cant say exactly how much oats is suitable. A teaspoon (5 ml) over a day perhaps? The important thing is that he doesnt eat so much oats that he leaves his pellets and hay uneaten. Because hes growing rapidly now, he will make good use of the extra protein and calories.

I would wait another two weeks with introducing other treats, then I’d start slowly with small pieces of fresh greens.

I agree with everything Bam said. 🙂 You want him to develop a good appetite for his hay and a healthy gut flora to set him up not for a healthy tummy. You could prob reserve a few oats for after he’s had his pellets for the day as a bit of a treat. I often will hand feed pellets too before giving them the full ration, so you could do that as well. Pellets themselves are pretty energy dense, so you don’t necessarily need “treats” to be treats. 🙂

Too much starch (oats) can cause a tummy upset, so it is possible to overdo it. For pellets, I believe it is correct to feed unlimited at his age (this is a reputable resource: https://rabbit.org/faq-diet/).