Sterilization Options for Cats

As I’ve said many times, cats are not small dogs! Like dogs, the primary reason for neutering (spaying/castrating) a cat is to control the population. Most shelters and rescue organizations neuter puppies and kittens before placing them for adoption. The reason is simple: a good number of pet parents – even when pre-payment is made – do not return for neutering at the appropriate time. However, unlike dogs, the considerations for neutering a cat differ greatly from those of dogs.

What are the benefits of neutering my cat?

Spaying your female cat eliminates the possibility of pregnancy and pyometra (uterine infection). Neutering your male or female cat also ends mating behaviors that are stressful to cats and humans. When in heat, female cats may display behavior such as loud and persistent crying and frequent rubbing and rolling on the floor. Your cat may also exhibit marking behaviors such as urinating outside the litterbox. An intact female’s scent will attract male cats.

Unneutered male cats will wander from home in search of a mate and may not return. They may also spray inside the home and may be aggressive to owners. Feline immunodeficiency virus (FIV), which is more prevalent in intact tom cats, can be spread by sexual behavior and fighting; both FIV and the feline leukemia virus (FeLV) may be passed onto a queen's offspring. 

However, aggression and spraying can also occur in spayed females and neutered males. Spaying and neutering are not a guarantee that your cat will not be aggressive or will not spray. 

Neutering also reduces the risk of certain cancers in cats; namely, mammary, ovarian, and uterine cancer in females. Female cats have a 91% decrease in mammary cancer with spay prior to one year of age. Up to 96% of mammary tumors are malignant in cats. Ovarian and uterine cancers are not commonly seen. Spayed females no longer go into heat every 3 weeks for 5 days during the breeding season.

Removing the testes during castration reduces the risk of testicular cancer to near 0% in male cats. Neutered male cats also have a lesser risk of enlarged prostate gland and prostatic cancer, although prostatic disease is extremely rare in cats.

What are the recommended sterilization procedures for cats?

For females…

  1. An ovariohysterectomy (traditional spay) is the most common sterilization procedure in the US. Both the ovaries and uterus are removed during the procedure. Removing the uterus eliminates the risk of any future uterine disease, including infection (pyometra). 
  2. In an ovariectomy procedure, the ovaries are removed while keeping the uterus intact. This sterilization option is more common in Europe and other locations. An ovariectomy is less invasive and faster than an ovariohysterectomy.  Anesthesia time is shorter with an ovariectomy.  Ovariectomy should be performed in young healthy females with a healthy uterus. Otherwise, an ovariohysterectomy (traditional spay) is recommended.

 For males…

  1. Orchiectomy (castration) is the most common sterilization procedure performed in the US for male felines. The testicles are removed, and patients are typically discharged the same day. The biggest advantage of castration is the reduction of sex-driven behaviors.
  2. During a vasectomy, the veterinarian cuts, ties, and blocks off the vas deferens tubes, preventing sperm from entering the seminal stream during ejaculation. The procedure is potentially quicker and usually results in faster recovery than castration because the testicles are not removed.  While the male cat is rendered sterile, he will retain his male sex-hormone driven behaviors such as roaming, urine marking, humping and aggression. Vasectomies are generally not taught in US veterinary schools.

Research from Tufts University shows that feral cats that undergo a vasectomy or hysterectomy could reduce a feral colony's numbers more effectively than the traditional approach of neutering. This may be because vasectomized cats retain reproductive hormones and will continue to breed with females in heat. Because they are not able to reproduce, the females will come out of the heat cycle without being impregnated; this would also protect their turf from sexually intact competitors.

 What are the risks/disadvantages of sterilizing my cat?

  1.  Increased risk for diabetes: Cats have a 2- to 9-fold increased risk of developing diabetes mellitus after neutering, with Burmese cats reported to be especially susceptible. One hypothesis is decreased insulin sensitivity[1]. Castrated cats have an increase in serum concentrations of insulin growth factor I, prolactin, and leptin, all of which are associated with metabolic rate and fat metabolism.[2]
  2. Increased risk for obesity: There are known effects of neutering on the physiology and behavior of the cat that predispose it to obesity. Obesity and decreased insulin sensitivity go hand in hand. Sterilized cats can have increased body weight, increased body mass index, increased depth of the falciform fat pad (a type of abdominal fat), decreased activity and decreased metabolic rate. In addition to diabetes, obesity can open the door to a world of problems, including joint disorders, urinary tract problems, and cancer.

The best way to mitigate these risks is to feed a weighted and measured, species-appropriate, low-carbohydrate diet to your cat. Studies have shown that a reduction of up to 30% of calories might be necessary to maintain a healthy weight on a sterilized cat.[3] Cats may be less energetic post-sterilization and therefore, burn fewer calories. Food intake should be controlled, meaning not leaving out food all day for cats to graze upon. Actively encouraging increased activity will help boost metabolism and burn calories.

Most veterinarians will recommend sterilizing a cat by 6 months of age. However, I recommend sterilizing cats once they are fully developed, and bones are finished growth (most likely around 9 months). Early spay/neuter results in the bone growth plates remaining open longer. Cats that are spayed or neutered prior to the closure of the growth plates have increased incidence of physeal fractures.

As with any procedure, discuss all your options with your veterinarian. There may be other health considerations to consider before deciding the best course of action. Sterilization is one of those areas where cats do differ from dogs…there appears to be many benefits to being spayed or castrated but fewer downsides.

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