Neutering, from the Latin neuter ('of neither sex'), is the removal of a non-human animal's reproductive organ, either all of it or a considerably large part. The male-specific term is castration, while spaying is usually reserved for female animals. Colloquially, both terms are often referred to as fixing. In male horses, castrating is referred to as gelding. An animal that has not been neutered is sometimes referred to as entire or intact. Often the term neuter[ing] is used to specifically mean castration, e.g. in phrases like "spay and neuter". Neutering is the most common method for animal sterilization. Humane societies, animal shelters, and rescue groups urge pet owners to have their pets neutered to prevent the births of unwanted litters, which contribute to the overpopulation of unwanted animals in the rescue system. Many countries require that all adopted cats and dogs be sterilized before going to their new homes.
Methods of sterilization
Females (spaying)
Spaying is the surgical removal of the ovaries and sometimes uterus in female animals. It is commonly performed as a method of birth control, behavior modification, or emergency removal of damaged ovaries. In non-human animals, the technical term is an ovo-hysterectomy or ovariohysterectomy; while in humans, this is called a hystero-oophorectomy. One form of spaying is to remove only the ovaries (oophorectomy or ovariectomy), which is mainly done in cats and young dogs as well as in laparoscopic procedures. Another, less commonly performed method is an "ovary-sparing spay" in which the uterus is removed but one (or both) ovaries are left. A complete ovariohysterectomy may involve removal of the ovaries, uterus, oviducts, and uterine horns.
The surgery can be performed using a traditional open approach or by laparoscopic "keyhole" surgery. Open surgery is more widely available, as laparoscopic surgical equipment costs are expensive. Traditional open surgery is usually performed through a ventral midline incision below the umbilicus. The incision size varies depending upon the surgeon and the size of the animal. The uterine horns are identified and the ovaries are found by following the horns to their ends. There is a ligament that attaches the ovaries to the body wall, which may need to be broken down so the ovaries can be identified. The ovarian arteries are then ligated with resorbable suture material and then the arteries transected. The uterine body (which is very short in litter-bearing species) and related arteries are also tied off just in front of the cervix (leaving the cervix as a natural barrier). The entire uterus and ovaries are then removed. The abdomen is checked for bleeding and then closed with a three-layer closure. The linea alba and then the subcutaneous layer are closed with resorbable suture material. The skin is then stapled, sutured, or glued closed. For suturing the feline linea alba, the most appropriate suture bite and stitch interval size was suggested to be 5 mm. Laparoscopic surgery is performed using a camera and instruments placed through small incisions (ports) in the body wall. The patient is under anaesthesia and lying on the back. The incisions are between 5 and 10 millimetres (0.20 and 0.39 in) and the number varies according to the equipment and technique used. The surgeon watches on a screen during the operation. The first port is made just behind the umbilicus and the camera is inserted. The abdomen is inflated with carbon dioxide gas to create a space in which to operate. A second port is introduced a few centimeters in front of the navel and a long grasping instrument called a Babcock forceps is inserted. The surgeon finds the ovary with the instrument and uses it to suspend the ovary from a needle placed through the abdominal wall. This lifts the ovary and uterus safely away from other organs. The surgeon then removes the grasping instrument and replaces it with an instrument that cauterizes and cuts tissue. This instrument uses electricity to heat the blood vessels to seal them and to cut them. No sutures are placed inside. The ovary is separated from the uterus and round ligament. The cautery instrument is removed and replaced by the grasping instrument, which is used to pull the ovary out through the small abdominal incision (port). This is repeated on the other side and the small holes are closed with a few sutures. Another method uses ligatures and even the uterus is removed. The benefits of laparoscopic surgery are less pain, faster recovery, and smaller wounds to heal. A study has shown that patients are 70% more active in the first three days post-surgery compared to open surgery. The reason open surgery is more painful is that larger incisions are required, and the ovary needs to be pulled out of the body, which stretches and tears tissue in the abdomen (it is not uncommon for patients to react under anaesthesia by breathing faster at this point). Removing the ovaries in female dogs removes the production of progesterone, which is a natural calming hormone and a serotonin uplifter. Spaying may therefore escalate any observable aggressive behaviour, either to humans or other dogs. The risk of infections, bleeding, ruptures, inflammation and reactions to the drugs given to the animal as part of the procedure are all possibilities that should be considered.
Males (castration)
In male animals, castration involves the removal of the testes (testicles), and is commonly practiced on both household pets (for birth control and behaviour modification) and on livestock (for birth control, as well as to improve commercial value). Often the term neuter[ing] is used to specifically mean castration, e.g. in phrases like "spay and neuter".
Sterilization alternatives
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