When to Neuter Your Golden Retriever - Should You Neuter?
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Neutering health effects more severe for Golden Retrievers than Labradors - July 14, 2014 - Life & Non-humans
Labrador retrievers are less vulnerable than golden retrievers to the long-term health effects of neutering, as evidenced by higher rates of certain joint disorders and devastating cancers, according to a new study by researchers at the University of California, Davis, School of Veterinary Medicine. Results of the study now appear online in the open-access journal PLOS ONE at http://tiny.cc/tia0ix. (This article was the first posted and is now below this article posted)“We found in both breeds that neutering before the age of 6 months, which is common practice in the United States, significantly increased the occurrence of joint disorders – especially in the golden retrievers,” said lead investigator Benjamin Hart, a distinguished professor emeritus in the School of Veterinary Medicine. “The data, however, showed that the incidence rates of both joint disorders and cancers at various neuter ages were much more pronounced in golden retrievers than in the Labrador retrievers,” he said. He noted that the findings not only offer insights for researchers in both human and veterinary medicine, but are also important for breeders and dog owners contemplating when, and if, to neuter their dogs. Dog owners in the United States are overwhelmingly choosing to neuter their dogs, in large part to prevent pet overpopulation or avoid unwanted behaviors.This new comparison of the two breeds was prompted by the research team’s earlier study, reported in February 2013, which found a marked increase in the incidence of two joint disorders and three cancers in golden retrievers that had been neutered. Health records of goldens and Labradors examined The golden retriever and the Labrador retriever were selected for this study because both are popular breeds that have been widely accepted as family pets and service dogs. The two breeds also are similar in body size, conformation and behavioral characteristics. The study was based on 13 years of health records from the UC Davis School of Veterinary Medicine for neutered and non-neutered male and female Labrador retrievers and golden retrievers between the ages of 1 and 8 years of age. These records included 1,015 golden retriever cases and 1,500 Labrador retriever cases. The researchers compared the two breeds according to the incidence of three cancers: lymphosarcoma, hemangiosarcoma and mast cell tumor. They also calculated the incidence for each breed of three joint disorders: hip dysplasia, cranial cruciate ligament tear and elbow dysplasia. The researchers also noted in these cases whether the dogs had been neutered before the age of 6 months, between 6 and 11 months, between 12 and 24 months or between age 2 and 9 years of age. Neutering and joint disorders. In terms of joint disorders, the researchers found that non-neutered males and females of both breeds experienced a five-percent rate of one or more joint disorders. Neutering before the age of 6 months was associated with a doubling of that rate to 10 percent in Labrador retrievers. In golden retrievers, however, the impact of neutering appeared to be much more severe. Neutering before the age of 6 months in goldens increased the incidence of joint disorders to what Hart called an “alarming” four-to-five times that of non-neutered dogs of the same breed. Male goldens experienced the greatest increase in joint disorders in the form of hip dysplasia and cranial cruciate ligament tear, while the increase for Labrador males occurred in the form of cranial cruciate ligament tear and elbow dysplasia. “The effects of neutering during the first year of a dog’s life, especially in larger breeds, undoubtedly reflects the vulnerability of their joints to the delayed closure of long-bone growth plates, when neutering removes the gonadal, or sex, hormones,” Hart said. Neutering and cancers The data also revealed important differences between the breeds in relation to the occurrence of cancers. In non-neutered dogs of both breeds, the incidence of one or more cancers ranged from 3 to 5 percent, except in male goldens, where cancer occurred at an 11-percent rate. Neutering appeared to have little effect on the cancer rate of male goldens. However, in female goldens, neutering at any point beyond 6 months elevated the risk of one or more cancers to three to four times the level of non-neutered females. Neutering in female Labradors increased the cancer incidence rate only slightly. “The striking effect of neutering in female golden retrievers, compared to male and female Labradors and male goldens, suggests that in female goldens the sex hormones have a protective effect against cancers throughout most of the dog’s life,” Hart said. Funding for the study was provided by the American Kennel Club Canine Health Foundation and the Center for Companion Animal Health at UC Davis.Read more at http://scienceblog.com/73321/neutering-health-effects-severe-golden-retrievers-labradors/#qKeflxdzmXVe6lco.99 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102241 This was the first article written I copied this from the website MOMIn contrast to European countries, the overwhelming majority of dogs in the U.S. are neutered (including spaying), usually done before one year of age. Given the importance of gonadal hormones in growth and development, this cultural contrast invites an analysis of the multiple organ systems that may be adversely affected by neutering. Using a single breed-specific dataset, the objective was to examine the variables of gender and age at the time of neutering versus leaving dogs gonadally intact, on all diseases occurring with sufficient frequency for statistical analyses. Given its popularity and vulnerability to various cancers and joint disorders, the Golden Retriever was chosen for this study. Veterinary hospital records of 759 client-owned, intact and neutered female and male dogs, 1–8 years old, were examined for diagnoses of hip dysplasia (HD), cranial cruciate ligament tear (CCL), lymphosarcoma (LSA), hemangiosarcoma (HSA), and mast cell tumor (MCT). Patients were classified as intact, or neutered early (<12 mo) or late (≥12 mo). Statistical analyses involved survival analyses and incidence rate comparisons. Outcomes at the 5 percent level of significance are reported. Of early-neutered males, 10 percent were diagnosed with HD, double the occurrence in intact males. There were no cases of CCL diagnosed in intact males or females, but in early-neutered males and females the occurrences were 5 percent and 8 percent, respectively. Almost 10 percent of early-neutered males were diagnosed with LSA, 3 times more than intact males. The percentage of HSA cases in late-neutered females (about 8 percent) was 4 times more than intact and early-neutered females. There were no cases of MCT in intact females, but the occurrence was nearly 6 percent in late-neutered females. The results have health implications for Golden Retriever companion and service dogs, and for oncologists using dogs as models of cancers that occur in humans. IntroductionThe overwhelming majority of companion dogs maintained in the U.S. are spayed or castrated (both referred to herein as neutered) [1]. Increasingly in the U.S. neutering is being performed early, demarcated in the present study as prior to one year of age. The impetus for this widespread practice is presumably pet population control, and is generally considered responsible pet ownership. However, this societal practice in the U.S. contrasts with the general attitudes in many European countries, where neutering is commonly avoided and not generally promoted by animal health authorities. For example, a study of 461 dogs in Sweden reported that 99 percent of the dogs were gonadally intact [2], and an intact rate of 57 percent was reported in a Hungarian study[3]. In the United Kingdom, a 46 percent intact rate was reported [4].In the last decade, studies have pointed to some of the adverse effects of neutering in dogs on several health parameters by looking at one disease syndrome in one breed or in pooling data from several breeds. With regard to cancers, a study on osteosarcoma (OSA) in several breeds found a 2-fold increase in occurrence in neutered dogs relative to intact dogs [5]. Another study on OSA, to explore the use of Rottweilers as a model for OSA in humans, found that neutering prior to 1 year of age was associated with an increased occurrence of OSA; 3–4 times that of intacts [6].Hemangiosarcoma is a cancer that is affected by neutering in females. A study of cardiac tumors in dogs found that cardiac HSA for spayed females was greater than 4 times that of intact females [7]. A study on splenic HSA found the spayed females had more than 2 times the risk of developing this tumor as intact females [8]. Neither of these studies separated early- versus late-spayed females with regard to increased risk, and neither focused on just one breed. A study on the epidemiology of LSA (lymphoma) in dogs, for comparison with human lymphoma, found that intact females had a significantly lower risk of developing this cancer than neutered females or neutered males or intact males [9]. Another cancer of concern is prostate cancer, which occurs in neutered males about four times as frequently as in intact males [10]. A study on cutaneous mast cell tumors (MCT) in several dog breeds, including the Golden Retriever, examined risk factors such as breed, size, and neuter status. Although early versus late neutering was not considered, the results showed a significant increase in frequency of MCT in neutered females; four times greater than that of intact females[11].In contrast to the rather strong evidence for neutering males and/or females as a risk factor for OSA, HSA, LSA, MCT, and prostate cancer, evidence for neutering as protection against a dog acquiring one or more cancers is weak. The most frequently mentioned is mammary cancer (MC)[12]. However, a recent systematic review of published work on neutering and mammary tumors found the evidence that neutering reduces the risk of mammary neoplasia to be weak, at best[13].With regard to joint disorders affected by neutering, one study documents a 3-fold increase in excessive tibial plateau angle – a known risk factor for development of CCL – in large dogs [14]. A paper on CCL found that, across all breeds, neutered males and females were 2 to 3 times more likely than intact dogs to have this disorder [15]. In this study, with sexes combined, neutering significantly increased the likelihood of HD by 17 percent over that of intact dogs. Given the widespread practice of neutering in the U.S., especially with public campaigns promoting early neutering, and the contrast with neutering practices in other developed countries, the objective of this project was to retrospectively examine the effects of neutering on the risks of several diseases in the same breed, distinguishing between males and females and early or late neutering versus remaining intact using a single hospital database. Because neutering can be expected to disrupt the normal physiological developmental role of gonadal hormones on multiple organ systems, one can envision the occurrence of disease syndromes, including those listed below, to possibly be affected by neutering as a function of gender and the age at which neutering is performed. The study focused on the Golden Retriever, which is one of the most popular breeds in the U.S. and Europe. In this breed, HD, CCL, LSA, HSA, MCT, OSA, and elbow dysplasia (ED) are listed as being of particular concern [16]. Methods Ethics Statement No animal care and use committee approval was required because, in conformity with campus policy, the only data used were from retrospective veterinary hospital records. Upon approval, faculty from the University of California, Davis (UCD), School of Veterinary Medicine, are allowed restricted use of the record system for research purposes. The final dataset used for statistical analyses is available to qualified investigators, upon request, from the corresponding author. Data Collection The dataset used in this study was obtained from the computerized hospital record system (Veterinary Medical and Administrative Computer System) of the Veterinary Medical Teaching Hospital (VMTH) at UCD. The subjects included were gonadally intact and neutered female and male Golden Retrievers, 1 to 8 years of age and admitted to the hospital between January 1, 2000 and December 31, 2009. Data from patients less than 12 months of age and 9 years or older were not considered. Additional inclusion criteria were requirements for complete information on date of birth, date of neutering (if neutered) and date of diagnosis (or onset) of the joint disorder or cancer. Patients were classified as intact or neutered; the neutering was sub-classified as “early” if done before 12 months of age and “late” if done at 12 months of age or older. For all neutered patients, the neuter status at the time of each visit was reviewed to ensure that neutering occurred prior to onset of the first clinical signs or diagnosis of any disease of interest. While the study set out to estimate incidence rates related to age at the time of neutering, patients were diagnosed at different ages and with differing durations of the disease as well as varying years of exposure to the effects of gonadal hormone removal. For those intact, early-neutered and late-neutered dogs diagnosed with a disease, the age of diagnosis was recorded. Follow-up times were recorded for each patient and determined by age of the dog at the initial clinical signs or diagnosis, minus the age of the dog when first included in the study. For dogs with no disease, follow-up times were the age at the last visit to the VMTH minus the age when the dog was first included in the study. With the goal of obtaining a sample size sufficiently large for statistical analysis, the database records were initially screened using disease-related keywords to evaluate the frequency of occurrence of HD, CCL, HSA, LSA, MCT, ED, OSA, and MC. Extensive reviews of patient records were then performed for specific evidence and information on each joint disorder or cancer for every patient included in the study. Only diseases with at least 15 cases found using this screening were included in the study. For all patients where age at time of neutering was not available in the record, an effort was made to obtain the information by telephone from the referring veterinarian. At the same time, age of onset of the disease in question was also sought. If the information was not available from the referring veterinarian, an attempt was made to reach the dog owner for this information. In order to optimize success in obtaining information, these efforts were focused on patients born in 2000, or later, and that were admitted to the VMTH between January 1, 2005 and December 31, 2009. Table 1 defines the categories of diagnoses based on information in the record of each case. A patient was considered as having a disease of interest if the diagnosis was made at the VMTH or by a referring veterinarian and later confirmed at the VMTH. Patients clinically diagnosed with HD and/or CCL presented with clinical signs such as difficulty standing up, lameness, or joint pain; diagnosis was confirmed with radiographic evidence and/or orthopedic physical examination. Clinical diagnoses of the various cancers were accompanied by clinical signs such as enlarged lymph nodes, lumps on the skin or presence of masses, and confirmed by imaging, appropriate blood cell analyses, chemical panels, histopathology and cytology. When a diagnosis was suspected based on clinical signs, but the diagnostic tests were inconclusive or not done, telephone calls were made to referring veterinarians and owners to confirm the diagnosis. Lacking a conclusive confirmation, the case was excluded from the analysis for that specific joint disorder or cancer. Finally, body condition scores (BCS), ranging from 1 to 9 and obtained from the patient records (when available) were taken into account because BCS, as an indication of weight on the joints, is considered to play a role in the onset of these joint disorders [17], [18]. Also, neutering has been implicated in an increase in body weight, especially as indicated by body condition score [18]. Citation: Torres de la Riva G, Hart BL, Farver TB, Oberbauer AM, Messam LLM, et al. (2013) Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers. PLoS ONE 8(2): e55937. doi:10.1371/journal.pone.0055937 Editor: Bart O. Williams, Van Andel Institute, United States of America Received: August 3, 2012; Accepted: January 4, 2013; Published: February 13, 2013 Copyright: © 2013 Torres de la Riva et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Supported by the Canine Health Foundation (#01488-A) and the Center for Companion 330 Animal Health University of California, Davis (# 2009-54-F/M). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. |