Rabbit - neutering is necessary

Surgery can be as safe on rabbits as on any animal. Unfortunately, the majority of veterinarians aren't experienced with safe techniques.
Females can be spayed as soon as they sexually mature, usually around 4 months of age. Males can be neutered as soon as the testicles descend, usually around 3-1/2 months of age.
The risk of reproductive cancers for an unspayed female rabbit stands at is virtually eliminated by spaying your female rabbit. Your neutered male rabbit will live longer as well, given that he won't be tempted to fight with other animals due to his sexual aggression.

REASONS TO SPAY A FEMALE DOG

Why Female Dogs Should Be Spayed
1. Mammary Cancer
A female dog spayed before her first heat will have about zero chance of developing mammary cancer. After the first heat, this incidence climbs to 7% and after the second heat the risk is 25%. It is easy to see that an early spay can completely prevent what is frequently a very difficult and potentially fatal form of cancer.
Spaying removes both the uterine horns and both ovaries and is crucial in the prevention as well as the treatment of mammary cancer.

2. Simple Convenience
The female dog comes into heat every 6 months or so. There is a bloody vaginal discharge and attraction of local male dogs. Often there is an offensive odor. All of this disappears with spaying.
3. Pyometra
Pyometra is the life-threatening infection of the uterus, which generally occurs in middle-aged to older female dogs in the six weeks following heat. The uterus with pyometra swells and is filled with pus, bacteria, dying tissue, and toxins. Without treatment, the pet is expected to die. Despite her serious medical state, she must be spayed quickly if her life is to be saved.
This is an extremely common disease of older unspayed female dogs. Pyometra is not something that might happen; consider that it probably will happen. If you still decide against spaying, be very familiar with the signs of pyometra.