Early Sterilization in Dogs and Cats

From the standpoint of effectively controlling pet populations, the best time for sterilizing dogs and cats is prior to puberty, which eliminates any possibility of the animal producing offspring.

Animal shelters and humane organizations which adopt young animals have long had policies that call for the adopting owners agree to have the animal neutered as soon as possible, but rates of compliance are typically low and, though a majority of such animals eventually are sterilized, many first have the opportunity to reproduce. Acceptance of early spay-neuter programs allow such organizations to effectively implement "neuter at adoption" programs.

The traditional approach to surgical sterilization of dogs and cats is to wait until the animal is at least 6 months of age before castration of spaying, but problems such as those described above have led many to advocate performing these procedures at a much earlier age.

Early neutering usually refers to gonadectomy performed at 6 to 14 weeks of age. This idea is certainly not unique - for example, a majority of male calves, sheep and piglets are castrated within a few weeks after birth. In the case of pups and kittens, this approach is being used more and more frequently and, although data on long-term effects are limited, early neutering appears to be a safe procedure providing that one recognizes certain physiologic differences between adults and neonates.

Techniques

The surgical techniques used for castrating and spaying young pups and kittens are very similar or identical to those used in adults. The chief concerns for these procedures are focused on the non-adult physiology of the young patient:

• They have an immature ability to maintain body temperature, a larger relative body surface area and less fat, which predisposes to hypothermia under anesthesia. This can be alleviated by maintaining the animal on a heating pad or similar device during surgery and recovery.
• Neonates are more sensitive than adults to hypoglycemia. It is advisable to withhold feed for only 4-6 hours prior to surgery, and some veterinarians advocate presurgical supplementation with sugar syrup or the administration of glucose during surgery.

These examples exemplify concerns many veterinarians have for performing gonadectomy on young pets and no doubt are legitimate. However, the experience of those that routinely perform these surgeries is that, with proper attention to some details, such surgeries pose minimal risks to the animal. Additionally, it has been reported that spaying young animals takes less time and holds less risk of hemorrhage than for adults.

Effects of Early Gonadectomy on Subsequent Development

Another source of resistance to early spay-neuter programs is concern that prepubertal removal of the gonads will result in obesity, urinary incontinence, stunted growth, behavioral abnormalities and other such problems. Some of these conditions are associated with gonadectomy, but there is little evidence to support the contention that risk is elevated by early gonadectomy per se.

While additional monitoring of animals gonadectomized early in life is warranted, experimental and survey data indicate the following effects of early spaying or neutering:

• Prepubertal gonadectomy significantly delays epiphyseal (growth plate) closure, apparently due to lack of gonadal steroids. The figure to the right depicts time of growth plate closure in 32 mixed-breed dogs (3 litters) spayed at different ages or not spayed. The difference in age of closure was significantly different among each of the three groups.
As a result of the longer period of growth, length of long bones is increased in animals neutered at a young age and the animal's size will be larger at adulthood. While this effect is well documented, it is not at all dramatic and should not be envisioned as a "King Kong" type of effect.
• Animals neutered prior to puberty show sexual infantilism, with poorly developed reproductive tracts. For example, the penis of such dogs is much smaller than that of sexually-intact animals and the vulva is quite small.
• Several studies have failed to demonstrate an adverse effect of prepubertal (including early) gonadectomy on play behavior and activity level relative to animals castrated as adults.

Summary

Careful followup of dogs and cats that underwent early gonadectomy indicate a few potentially adverse effects (e.g. elevated risk of incontinence in female dogs spayed prior to 3 months). However, the vast majority of traits characterizing a good pet are not significantly altered relative to what is seen in animals neutered later in life. Although some long-term effects remain to be studied definitively, all evidence suggests that early spay-neuter of dogs and cats is a safe procedure with minimal or any adverse effects on subsequent health of the animal.

Given the obvious benefits with regard to pet population control, gonadectomy of weanling puppies and kittens appears to be an idea whose time has come.

References and Reviews

• Aronsohn MG, Faggella AM: Surgical techniques for neutering 6-14-week-old kittens. J Am Vet Med Assoc 202:53, 1993.
• Bloomberg MS: Surgical neutering and nonsurgical alternatives. J Am Vet Med Assoc 208:317, 1996.
• Howe LM, Slater MR, Boothe HW, etc: Long-term outcome of gonadectomy performed at an early age or traditional age in cats. J Am Vet Med Assoc 217:1661, 2000.
• Howe LM, Slater MR, Boothe HW, etc: Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. J Am Vet Med Assoc 218:217, 2001.
• Lieberman LL: A case for neutering pups and kittens at two months of age. J Am Vet Med Assoc 191:518, 1987.
• Salmeri KR, Olson PN, Bloomberg MS: Elective gonadectomy in dogs: a review. J Am Vet Med Assoc 198:1183, 1991.
• Salmeri KR, Bloomberg MS, Scrugs SL, Shille VS: Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development. J Am Vet Med Assoc 198:1193, 1991.
• Spain CV, Scarlett JM, Houpt KA: Long-term risks and benefits of early-age gonadectomy in cats. J Am Med Assoc 224:372, 2004.
• Spain CV, Scarlett JM, Houpt KA: Long-term risks and benefits of early-age gonadectomy in dogs. J Am Med Assoc 224:380, 2004.
• Theran P: Early-age neutering of dogs and cats. J Amer Vet Med Assoc 202:914, 1993.