I wouldn’t recommend using the product unless a knowledgeable rabbit vet were to recommend it. Many products say thy’re safe for bunnies, but aren’t really great for them. Unfixed bunnies tend to have much stronger scented urine and often spray as a territory marker, since he was neutered so recently, it may take a little time for the scent to diminish.
Some other tips for reducing odor from San Diego Rabbits Online Newsletter :
1. When you change the litter, be sure to rinse the box *thoroughly* with water. Occasionally giving it a white vinegar rinse will help keep calcium residues down and control the odor. Be sure to wash the bottom of the box as well.
2. Be sure there is no urine *under* the box or around the boxes in areas that are not wiped up. These get to smelling foul very quickly. If you do have a spot where the urine tends to seep in, remove the box, scrub the area thoroughly with white vinegar and rinse well with water. You might even want to bleach it, but be sure to rinse away all the bleach before you let bunny near the area.
3. Line the boxes with newspaper and a rabbit-safe litter, such as CareFresh, Yesterday’s News (now available for rabbits), or Feline Pine. (Do not use clay-based or clumping cat litter which can be dangerous for bunny if consumed). Top off the litter box with a large handful or more of hay. Bunnies like to munch on hay and use their litterbox at the same time.
4. CHANGE THE LITTER BOX EVERY DAY. If you line the box with newspaper, its easy to dump the waste into a trashbag for disposal or use for composting.