Hi,
Prevention is the key, but your going to need help from the daycare. Is there enough help in the daycare? It sounds like your sons biting is provoked. It is a defense that some kids learn about very early and one that works for them very well.
In my daycare the biter is always by my side and if not by my side, contained in some way, until the behavior stops. If, I allow the biter to wander off to socialize with the others, I keep a watchful eye. Biters position for the attack. Keep a whistle handy and blow if there is another kids body part anywhere near the mouth. If in doubt, blow anyway. It will turn heads, breaking the position of the biter. If you don't want to use a whistle, then clap your hands really loud several times and use an extremely firm voice.
I had a biter in my daycare during my visit for accreditation visit. I prevented a bite by clapping my hands very loud and saying " Get those choppers back in your mouth" very firmly. I was told that it was perfectly acceptable.
He is still young enough for a highchair or playpen. The other kids need to be protected, but they also need to understand why your son took a bite. Also, your son needs to see the pain he has caused to someone else.
The biter never gets all of the loving attention after biting. The victim does. First, I show the biter the bite mark and explain that it hurts really bad. I get an ice pack and really play it up. The biter has to help treat the victim.
With this said, I think that your son needs some protection form other kids taking things from him also. There is nothing more irritating to me than seeing older kids pick on little ones because they think they are defenseless. It is not fair. Older kids get away with this stuff all the time. If your son has a toy, he should be able to play with it without worry. Biting is never acceptable, but sometimes understandable!
The following is a suggestion from 30 years ago. It was published in a book. It is no longer socially acceptable, but it works!
I used it on my own 30 year old son when he was about 2. One time did it. He never took a bite again.
My son came up behind me when I was doing the dishes and took a big bite on my thigh. I put his own arm in his mouth. I placed my one hand on the top of his head and the other hand under his chin and caused him to bite himself. He never tried to bite again because he now understood the pain that it caused. One time is all it took.
The real key is prevention until he outgrows his animal behavior.
D.