Pine shavings are not safe for bunnies. The aromatic oils in the pine can be hard of the bun’s respiratory systems and can cause problems if the bun ever needs to go under anesthesia (something to do with the liver…). Aspen shavings are safe though, but are more expensive.
Pine pellets (on the other hand) are safe because they have been heat treated, which removes those aromatic oils. I use pine pellets because they work well and are very cheap (I buy them sold as horse stall bedding). I put a layer of pine pellets, then a layer of fluffy hay on top. I dump the whole thing every other day. I used to use a litter screen system and I would scoop out the wet areas, but I got lazy and realized I was doing all this extra work to save a very small amount of pellets.
Another popular option that works well for litter training is Care Fresh.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.