When to Neuter Dogs and Cats: A Survey of New York State Veterinarians’ Practices and Beliefs
Practicing veterinarians in small-animal or mixed-animal practice in New York state were surveyed about their beliefs and practices regarding the age at which dogs and cats should be neutered and their attitudes toward early neutering (at 4 months of age or younger). The majority of veterinarians routinely recommended neutering for all client animals (70.6%) and supported the routine neutering of shelter animals before adoption (90.3%). More veterinarians in this study reported at least one perceived benefit (91.3%) for early neutering than reported at least one perceived risk (84.4%). Veterinarians with experience neutering early were less likely to believe that the procedure was associated with one or more risks.
Introduction
Many people in the animal-shelter community see routine pediatric neutering (i.e., gonadectomy of males and females) as an important step in reducing the number of dogs and cats relinquished to shelters, but the safety of the procedure is still debated among veterinarians. To date, studies have established safe anesthetic and surgical protocols12 and have shown that neutering at 7 weeks of age is associated with more rapid anesthetic recovery and fewer perioperative complications when compared to neutering at 7 months of age.3 In addition, studies have shown no adverse medical consequences for up to 3 years following gonadectomy surgery in cats.4 In dogs, prepubertal neutering is not associated with an increased incidence of behavioral problems or problems associated with any body system for up to 4 years following surgery, although it may be associated with an increased incidence of some infectious diseases.5
A recent survey of veterinary colleges6 found that 48% of North American veterinary colleges offer veterinary students instruction in neutering puppies and kittens aged 8 to 14 weeks. However, only a few previous studies have looked at whether veterinarians are neutering at this age in private practice, and these studies have been limited by a low response rate7 or reliance on volunteer responses.8–10
The objectives of this survey were to describe practicing veterinarians’ beliefs and practices regarding the age at which dogs and cats should be neutered and their attitudes toward neutering at ages of ≤4 months in both animal-shelter and private-practice settings. In addition, the study was designed to determine if these beliefs and practices varied by the veterinarian’s gender or were associated with other factors, such as year of graduation or experience with early neutering.
Materials and Methods
A list was obtained from the American Veterinary Medical Association (AVMA) of veterinarians in clinical practice with a mailing address in the state of New York, who listed themselves as being in feline practice, small-animal practice, or mixed practice (at least 50% small). From this list of 1,722 veterinarians, 627 were randomly sampled using commercially available software.a Information regarding the year of graduation and species seen was collected from the 2000 or 2001 AVMA membership directory.1112 In the summer of 2000, sampled individuals were mailed a cover letter describing the purpose of the study, a questionnaire, and a prepaid business-reply envelope. Three weeks later, reminder postcards were sent to nonrespondents. Remaining nonrespondents were sent a second mailing at 6 weeks, identical to the first, but with a modified cover letter more urgently requesting their participation. The questionnaire booklet was designed using published recommendations13 and was pretested on volunteers before finalization.
Questions were asked as a series of multiple-choice and embedded open-ended questions. For all questions, early neutering was defined as ≤4 months of age, and neutering was defined to include both spaying (i.e., ovariohysterectomy) and castration. The questionnaire consisted of three sections. The first section asked respondents to describe their beliefs regarding early neutering. Specifically, respondents were asked if and at what age shelter animals and client-owned animals should be neutered. General questions about the benefits and disadvantages of early neutering were also asked.
In the second section, respondents were asked to describe their own neutering practices and to identify the criteria they used for determining the age at which to recommend neutering animals seen in their practices. Specific criteria were listed in a multiple-choice format, including vaccination status, minimum weight and age requirements, etc. An “other” field was available for criteria not listed. In addition, respondents were asked how often they recommended neutering of mixed-breed and purebred animals, if and how they were trained in early neutering, and whether shelters in the area practiced early neutering. Respondents who had not practiced during the three months prior to receiving the questionnaire were excluded from this section.
Demographic information was obtained in the third section, including gender, age, years in clinical practice, practice location, type of services offered, and number of practicing full-time and part-time veterinarians. A “comments” field was included at the end for concerns not previously addressed in the questionnaire.
Commercially available statistical software was used to carry out analyses of results.b For all comparisons, an alpha level of P≤0.05 was considered statistically significant. The chi-square test was used to compare categorical variables. Continuous nonparametric data was compared using the Wilcoxon’s signed rank test (for paired data) or the Wilcoxon’s rank sum test (for unpaired data).14 Logistic regression was used to identify factors associated with dichotomous outcomes; for example, factors associated with believing that early neutering has at least one benefit. Models were built using backward selection as recommended by Kleinbaum, et al.15
Results
Response
Of the initial sample population (n=627), 11 respondents were subsequently determined to be ineligible because they no longer resided in New York state, were no longer in clinical practice, did not see small animals in practice, were deceased, or the questionnaire was completed by a veterinarian other than the one sampled. Of the remaining eligible sample population (n=616), 412 (66.9%) questionnaires were returned partially or fully completed. When responders and nonresponders were compared by three factors available from the mailing list or AVMA directory (i.e., species of animal seen, year of graduation from veterinary school, and geographic location), the response rate did not vary by species of animal seen or by year of graduation. However, the response rate for New York City metropolitan area and Long Island together (56.0%) was lower than for the remainder of the state (77.3%) (P<0.001).
Demographics
Reported characteristics of participating veterinarians are in Table 1. The median year of graduation from veterinary school was 1986 (range, 1950 to 2000). In addition to offering primary health care, 26.8% of respondents offered specialty or referral services, and 3.5% of respondents offered some form of alternative medicine (e.g., acupuncture or Chinese modalities).
Beliefs
Most respondents (90.3%) favored neutering some or all shelter animals prior to adoption, while 3.2% were unsure if shelter animals should be neutered before adoption. The 26 (6.5%) respondents who did not believe that any shelter animals should be neutered before adoption were significantly more likely to be male (88.0%) and graduated earlier (median year, 1974) than those who favored neutering shelter animals (50.6% male; median graduation year, 1986) (both P<0.001). Among these 26 respondents, reasons given for opposing routine neutering of shelter animals prior to adoption included the view that shelters compete economically with veterinarians (30.8%), the quality of care or surgical technique in shelters is poor (26.9%), and the adopter should be able to make the decision whether or not to neuter (11.5%).
When asked about the earliest age at which dogs and cats should be routinely neutered, the age reported was significantly lower for shelter animals than client-owned animals (all P<0.001 for male and female dogs and cats). A range of 61% to 65% of veterinarians (depending on the animal’s species and sex) reported a lower minimum age for shelter animals than for client-owned animals. The minimum ages for neutering ranged from 1.2 to 12 months [Table 2]. Slightly more than a third of veterinarians (35% to 39%, depending on the animal’s species and sex) thought that the earliest age at which client-owned animals should be routinely neutered was ≥6 months.
Ninety-one percent of respondents believed that there is at least one benefit associated with early neutering that is not also associated with neutering at a later age. Despite indicating one or more benefits, however, 14% of these veterinarians also reported that they were unsure about whether benefits exist. In logistic-regression models, year of graduation was the only variable associated with reporting at least one benefit. Those who reported at least one benefit of early neutering graduated later than those who did not (difference between medians, 9 years; P<0.0001). More than 75% of respondents (79.0%) believed that early neutering will help reduce pet overpopulation [Table 3]. Among veterinarians writing in specific benefits not listed in the survey [Table 4], the most common perceived medical benefit was reduced chance of mammary cancer.
Eighty-four percent of veterinarians believed that at least one risk is associated with early neutering that is not also associated with neutering at a later age. Among these, 16% also reported they were unsure if risks exist. More than half (59.8%) of respondents believe that early neutering increases the risk of anesthetic complications [Table 3]. A number (20.7%) of respondents also believed that early neutering has not been researched well enough to be considered safe. Among veterinarians writing in specific risks not listed in the survey [Table 5], the most common perceived medical risk was increased risk of feline lower urinary tract disease (FLUTD). In logistic-regression models, lack of experience with routinely neutering dogs or cats ≤4 months of age was the only variable associated with reporting at least one risk of early neutering. Among those having experience with early neutering, 68.7% reported at least one risk, while among those without experience, 90.6% reported at least one risk (P<0.001).
Seventy-three percent of veterinarians reported both benefits and risks for early neutering, indicating that individual veterinarians often had conflicting beliefs about the procedure. Opinions among veterinarians did not always agree either [Table 3]. In the multiple choice questions, for example, 23.2% reported that early neutering increased surgical complications, while 15.5% reported that the procedure decreased surgical complications. Similarly, in the open-ended questions, 8.9% of veterinarians reported that early neutering increased a dog’s trainability, while 16.7% thought early neutering reduced trainability.
Practice
The animal’s age was consistently the most common criterion used by veterinarians when deciding when to recommend neutering dogs and cats in their own practices [Table 6]. The age at which respondents recommended neutering animals in their own practices was significantly higher than the earliest age they believed should be used for client-owned animals in general (all P<0.001 for male and female dogs and cats). Approximately one-third of veterinarians (34% to 37%, depending on animal’s sex and species) reported the minimum age for neutering client-owned animals to be at a younger age than they actually practiced. Many veterinarians reported neutering earlier than their “minimum” age under some circumstances; for example, they stated they would neuter earlier if a cat was going to be declawed or if an animal had already developed a behavioral problem such as spraying. Vaccination completion was the second most common criterion for deciding when to neuter. No veterinarians recommended waiting until after a heat cycle to neuter female cats, and only two recommended waiting until after at least one heat cycle for female dogs. Similarly, no veterinarians recommended waiting until after at least one litter of offspring before neutering female cats or dogs.
Most (70.6%) respondents recommended neutering of both purebred and mixed-breed dogs and cats to all clients. About a fourth (26.4%) of veterinarians recommended neutering for mixed-breed animals more often than for pure-bred dogs, or else they made exceptions to their policies for purebred dogs. Eleven (2.7%) veterinarians recommended neutering purebred and mixed-breed dogs and cats rarely or only to some clients.
Of those who had learned to neuter dogs or cats at ≤4 months of age (n=223; 55.9%), most were either self-taught (48.4%) or learned as veterinary students (20.2%). Others reported having been taught by a colleague (17.0%), learning at an animal shelter (9.9%), or having taken a course or workshop after graduating (1.8%). Twenty-nine (13.0%) commented that they considered early neutering the same as neutering at a later age, or that no additional training was required. About half (46.9%) of veterinarians reported being interested in learning more about early neutering procedures, regardless of whether or not they had already performed early neutering.
Animal Shelters in Practice Area
A majority (67.4%) of respondents reported that at least one animal shelter in their area routinely neutered dogs and cats at ≤4 months of age. Ninety-three out of 271 (34%) veterinarians reported seeing more complications from early-neuter surgeries performed at their local animal shelters than from neuter surgeries in their own practices. Among these respondents, the factors believed to contribute to the complications were exposure to infectious agents (81.7%), the stressful environment of the shelter (76.3%), a low level of care provided by the shelter staff (47.3%), and neutering too young (29.0%).
Discussion
The overall response rate for this study (66.9%) was high compared to many recent surveys of veterinarians in the United States, which had response rates ranging from 6.4% to 82%.716–23 The lower response rate from New York City and Long Island may be partially due to the frequent turnover of veterinarians who were interns or residents in New York City. Also, New York City veterinarians may be more likely to move to a suburb in an adjacent state (e.g., New Jersey or Connecticut) and no longer consider themselves eligible for the study. Other urban areas (e.g., Buffalo, Rochester) were sampled more successfully. While nonresponse bias is always a concern, one study has suggested that nonresponding veterinarians’ unwillingness to participate in surveys is often due to ineligibility or distance from the subject matter (e.g., the nonresponding subjects are no longer in clinical practice).22 Some error from the sampling source was possible, since the AVMA membership logs are updated by veterinarians only yearly and since veterinarians may code their occupational information incorrectly or may fail to update this information with membership renewals.
Veterinarians believed that the earliest age for neutering dogs and cats in shelters should be 3 months as compared to 5 months for client-owned animals (regardless of the animal’s gender) [Table 2], and 90.3% of responding veterinarians favored neutering some or all shelter animals before adoption. The discrepancy between the recommended minimum ages for shelter animals as compared to client-owned animals could be attributed largely to veterinarians’ beliefs that early neutering is an important strategy for reducing pet overpopulation and facilitating adoptions [Table 3]. Therefore, any risks associated with the procedure are warranted for shelter animals. Interestingly, the median earliest age at which veterinarians actually recommended neutering to their clients was 5.5 months for female cats and 6 months for other cats and dogs [Table 6]. These ages are later than the minimum ages reported for client-owned animals in this study and later than those found in a survey of 33 practicing veterinarians in the Buffalo, New York area (median, 4.5 months for dogs; median, 4.0 months for cats, unpublished data). All of the veterinarians in the Buffalo study had volunteered with an animal shelter’s spay-neuter clinic, which included neutering as early as 6 weeks of age. In a study conducted by the American Humane Association of volunteer participants among veterinarians attending a conference, 78% to 80% of veterinarians (depending on the animals’ sex and species) reported that they would neuter at ≤4 months of age for the purposes of population control.10 These results are similar to those in this study, where 75% to 78% of veterinarians reported that the earliest age at which shelter animals should be neutered is 4 months. Many of the veterinarians that recommend neutering at 6 months for client-owned animals also commented that neutering before the first estrus is important, even though the first estrus is at or before 6 months of age for many dogs and cats.24
A high proportion (84.4%) of veterinarians perceived at least one risk associated with early neutering that is not associated with neutering at a later age. Twenty-nine percent of respondents reported at least one perceived medical risk. The most common medical concern raised was the possibility of increased risk of FLUTD or problems associated with this condition, such as urethral obstruction [Table 5]. Several respondents recommended neutering male cats only after 10 months of age, largely due to this concern. A recent long-term study4 found no increased risk of FLUTD in early-neutered cats up to 3 years after surgery. Similarly, another study found that age of neutering was not associated with a decrease in urethral diameter.25 Further studies are needed to completely address concerns about FLUTD and urinary obstruction. In the study of veterinarians in the Buffalo area cited above, only one veterinarian (among 33 with experience in early neutering) reported increased complications from early neutering in his own practice. These results are consistent with the findings of this study, that veterinarians with experience in early neutering are less likely to report risks associated with the procedure.
Reluctance on the part of veterinarians to recommend early neutering to their clients may be due to a variety of reasons. Both practicing veterinarians and clients may be accustomed to neutering at a minimum of 6 months of age, as this has been the standard in veterinary practices for many years. Several respondents commented that they would like to be able to recommend early neutering for clients’ animals, but their employers did not allow them to do so. Veterinarians also clearly had mixed beliefs about early neutering. Many individuals perceived both risks and benefits, and there was a fair amount of difference of opinion among veterinarians. For example, 29.1% believed that the risk of one or more medical problems was increased with early neutering when compared to neutering at later ages, while 23.3% believed that this risk was decreased.
Veterinarians continue to express concerns about perceived anesthetic, surgical, and perioperative complications of early neutering even though these issues have been evaluated by recent studies and no increased risk has been identified. For example, more than 30% of veterinarians believe that early neutering results in more surgical complications or perioperative infections [Table 3], even though a recent study reports that neutering at ≤23 weeks of age results in fewer perioperative complications than neutering >23 weeks of age.3 Similarly, 59.8% of veterinarians in this study were concerned about anesthetic complications of early neutering, while studies have demonstrated several safe anesthetic protocols226 and shown no increase in anesthetic complications from early neutering.3 Veterinarians may be unaware of the study results or feel personally uncomfortable with performing the procedure. Some of this discrepancy in opinion may also be related to limited research regarding long-term effects associated with the procedure. A few studies in the literature address long-term consequences. In a study of cats, no difference was found between cats neutered before 24 weeks of age and those neutered after 24 weeks of age after a median follow-up time of 37 months.4 In a long-term study of dogs, infectious diseases were more common in dogs neutered before 24 weeks of age, but the authors speculate that this difference may be attributable largely to exposure to canine parvovirus in one particular shelter at the time of neutering.5 Thus, it is difficult to discern if this increase in infectious diseases is due to early neutering or simply due to exposure to a shelter setting at an early age.
Several veterinarians commented that they could ensure 100% compliance with their current neutering policies and recommendations, so early neutering was considered unimportant for the purposes of population control in their clients’ animals. In contrast, other veterinarians commented that early neutering (or else neutering at the time of the last vaccinations) was important, because pet owners could not be trusted to return for neutering before their animals went through puberty. This concern that pet owners will wait too long to have their animals neutered is supported by at least two studies of randomly contacted pet owners, in which 15%27 and 16%28 of adopted female dogs and cats had unplanned litters before the owners had them neutered. The major reason cited by owners for these pregnancies before neutering was accidental breeding. Studies suggest that routine neutering 2 to 3 weeks following the final vaccination of client-owned animals can now be done safely13–526 and will ensure that accidental breeding is minimized. There is no data supporting 6 months as the ideal age for neutering. That coupled with many veterinarians’ concern that client-owned animals complete their vaccination series before neutering, suggests that recommendations for age at neutering could be lowered to 4 to 5 months of age for client-owned animals, depending on when the vaccination series is completed.
Only 29% of veterinarians who saw complications from early neutering in their local shelters attributed the complications to the animals’ ages. Some veterinarians who thought that shelter animals in general could be safely neutered early, still expressed concerns about the procedure’s safety at particular shelters in their area. In the “comments” section, some respondents even mentioned concerns about the practices (e.g., surgical technique or aseptic practices) of individual shelter veterinarians or staff members. These results suggest that shelters routinely neutering dogs and cats at an early age must adhere to good practice standards for early neutering and be aware of possible complications when these standards are not met. At the same time, practicing veterinarians must familiarize themselves with the procedures actually used in their local shelters and provide constructive feedback about any complications they see to shelter personnel.
Conclusion
The results of this study show that veterinarians are overwhelmingly recommending neutering for their clients’ animals and that veterinarians are not perpetuating unfounded ideas about neutering (e.g., that female dogs and cats should have a litter before spaying). Nevertheless, many veterinarians, particularly those who graduated earlier and who lack experience with early neutering, still have concerns about neutering at ≤4 months of age. Although some of these concerns still need to be addressed by further research, others have already been dispelled by studies. Training and experience with early neutering will allay many concerns, and the results of this study show that practitioners have a large interest in further training in techniques for early neutering. At a time when millions of healthy, adoptable dogs and cats continue to be euthanized for lack of homes, neutering (before breeding) is an essential tool for reducing unnecessary deaths.
Microsoft Excel 97; Microsoft Corporation, Redmond, WA
Minitab 13.1 for Windows; Minitab Inc., State College, PA
Acknowledgment
The authors thank Dr. Noel B. Rosales for assistance with graphic design and questionnaire layout.
