People seem much more willing to get their dogs and cats spayed than to get them neutered. I suspect that much of this stems from two facts. The first one is that the owner of the bitch/queen obviously gets stuck with the unwanted puppies/kittens. The second one is the behaviour and mess associated with the heat cycle. Whatever the reasons may be, we seem to have very little difficulty convincing people to have their female dogs (and cats) spayed.
The most important reason by far that we recommend spaying female dogs and cats is to prevent a very common form of cancer; mammary cancer. Each heat cycle and each pregnancy that a bitch or queen goes through increases the chance that she will develop mammary cancer. It is generally regarded that each heat cycle will increase the chances of mammary cancer by 10% and each pregnancy will increase chances by between 15% and 25%. This occurs because during every heat cycle and pregnancy the mammary glands have to go from their resting or quiescent state to an active state so they are prepared to deliver milk to the young. The risk of quiescent cells becoming damaged during reproduction and becoming cancerous is much lower than cells that are reproducing at high rates like they do when the glands are active. Two other common forms of cancer in female dogs and cats are ovarian and uterine cancer. Since these tissues are both removed during the spay procedure the chances of these forms of cancer arising are obviously reduced to near zero.
Although territoriality is generally less of a problem in female dogs, they can be quite territorial, especially if their is not a male dog around to assume the role of leader. They tend to be a bit less protective of territory, but a lot more protective of their own personal space. Female cats of course are intensely territorial! Then of course you have the once or twice yearly heat cycle in a female when every dog within 5 miles (yes, literally 5 miles!) will come and hang around waiting for her to “come out and play”. During this period many females will attempt to break confinement and take off for up to 48 hours. This of course increases their chances of getting hurt or getting hit by a car.
The heat cycle itself in females can be very messy, especially in larger dogs. Once or twice yearly dogs will go through a reproductive cycle called “heat”. Over this 3 week period their ovaries will produce eggs that can be fertilized. The reproductive tract prepares for pregnancy and they undergo behavioural changes that are designed to get them “out there” where they can be impregnated. They tend to be very vocal during this period (especially cats!) whining and crying to get out a lot. During the latter 2 weeks of the cycle they also will have a bloody discharge that can become quite messy. What most folks don’t realize (and find out later) is that when the bleeding stops is when they are most fertile! It isn’t over when the bleeding stops folks, it is just getting started! Cats are even worse in a way as they are “induced ovulators”. This means that it is the actual act of mating that causes female cats to release their eggs for fertilization. The upshot of this is that cats will very often cycle repeatedly until they are bred! This can and often does go on for months.
The final reason that we recommend spaying females is the same one as in the males: pet overpopulation. If a female dog is spayed, there is no chance that she will contribute to this growing problem. The last figures I am aware of is that over 2.5 million stray dogs and cats are euthanized yearly in the United States, and over 250,000 a year are euthanized here in Canada. And these are very old numbers folks (they are from when I was in school 20+ years ago). The situation is a lot worse now.
The procedure itself is more invasive than in a male and we generally require them to rest overnight in our care after the surgery is performed. It involves making an incision in the wall of the abdomen (the belly), locating and removing the ovaries and the uterus and closing the abdomen afterwards. Female animals generally do not require the Elizabethan Collar like the males do, but occasionally we have to send one home with a “cone”. If the procedure is performed before they have their first heat (we like 6 months of age) most animals appear fully recovered within 24 hours and behave completely normally at home. If we have to spay an older animal or one that has just finished a pregnancy they are often quite uncomfortable afterwards and we will leave them on pain control for an extended period after they go home.