Veterinarians recommend desexing for a variety of reasons. Firstly, it prevents unwanted litters of puppies and kittens. In females, the spey procedure removes the reproductive organs (most commonly the ovaries and uterus) and immediately stops hormonal cycles with the associated bleeding in bitches, and risk of pregnancy. Castration of males can help prevent wandering tendencies (often in search of females) as well as some territorial behaviours in cats such as urine marking and fighting. The latter can lead to many an unplanned vet visit due to injuries which can in themselves require surgery and extensive treatment to resolve. There is also a risk that fighting, and mating behaviour can transmit diseases, such as Feline Immunodeficiency Virus (FIV) in cats (to which there is currently no cure).
Medical Benefits of Desexing
There are also significant medical reasons for desexing, both in terms of prevention and cure. Speying reduces the risk of mammary tumours (which can be cancerous like in people) as well as tumours of the ovaries, uterus and cervix. It also prevents a uterine infection known as a pyometra, which is common in mature bitches and without a quick diagnosis and treatment, is often fatal.
Castration reduces the risk of some prostatic diseases, as well as perianal tumours, and eliminates the possibility of testicular cancers.
Desexing is often recommended to prevent hereditary diseases being passed on, for example, hip dysplasia or cryptorchidism (where one or both testicles do not fully descend into the scrotum, increasing the risk of testicular cancers).
Desexing can also be used as a treatment for a variety of conditions, these include pyometra in queens and bitches, and prostatic hypertrophy in dogs.