This article is from the rec.pets.dogs: Health Care Issues FAQ, posted to rec.pets.dogs newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
If you are not planning to breed your pet or put it to stud service, or your dog's breeding days are over, you will want to neuter it. There are a number of health benefits associated with neutering, for either sex.
Technically, the general term for either sex is neutering; bitches are spayed and dogs are castrated. However, general usage is that bitches are spayed or neutered and dogs are neutered.
Neutering is *not* a solution to behavioral problems; training is. However with some dogs it can alleviate some factors that make it more difficult to train. But you cannot expect to neuter your dog and have it turn into an angel without any work.
Tip: let your dog eliminate before taking it in and again after getting it back. Many dogs, especially crate-trained dogs, will not eliminate in the vet's kennels during their stay.
Castration
Dogs are castrated. A general anesthetic is administered, the testicles are removed (oriectomy) and several stitches are used to close it up. The scrotum will shrink and soon disappear after castration. You will want to neuter the dog around six months of age, although dogs can be neutered at any time after this. For example stud dogs are typically neutered after they are too old to breed, and they suffer no ill effects. Some clinics may use a local anesthetic instead.
Spaying
Bitches are spayed; this is an ovario-hysterectomy (uterus and ovaries are removed). She must be put under general anesthesia. A large patch of fur will be shaved (to prevent later irritation of the incision) off the lower abdomen. You may have to take your bitch back in to remove the stitches. From a health point of view, the earlier the bitch is spayed, the better. Ideally, she should be spayed before her first heat, this reduces the risk of reproductive and related cancer (e.g., breast cancer) later in life considerably; not to mention guaranteeing no unwanted puppies. The most dramatic rise in risk of cancer occurs after the second heat or two years of age, whichever comes first before spaying. After that, while the risk is high, it does not rise further.
Post-op recovery
You will need to watch to make sure your dog does not try to pull out its stitches, and consult your vet if it does. You might, in persistent cases, need to get an Elizabethan collar to prevent the animal from reaching the stitches. Puffiness, redness, or oozing around the stitches should be also reported to the vet. Some stitches "dissolve" on their own; others require a return to the vet for removal.
For further information on how neutering may affect your dog, see the section on neutering in Assorted Topics.
Cost
The cost can vary widely, depending on where you get it done. There are many pet-adoption places that will offer low-cost or even free neutering services, sometimes as a condition of adoption. Local animal clinics will often offer low-cost neutering. Be aware that spaying will always cost more than castrating at any given place since spaying is a more complex operation. Vets almost always charge more than clinics, partly because of overhead, but also because they often keep the animal overnight for observation and will do free followup on any later complications. Larger animals will cost more than smaller ones.
Pet Assistance has a program to help you locate low-cost neutering. There may be an 800 number, but the San Diego number is 619-697-7387. They can refer you to a veterinarian in your area who will perform low-cost spaying or neutering. Other low cost/coupon assistance: 1-800-321-PETS; Pet Savers Foundation at 1-800-248-SPAY. Most vets honor these coupons.
Effect on behavior
There is an extensive discussion on the effect neutering has on a dog's behavior in the Assorted Topics chapter of the FAQ. In summary, no one really knows, and for every example presented, a counter-example can be made.
 
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