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An Urban Experience
5%: neutering at < 6 months of age nearly doubled the risk of suffering joint disease in the former, and increased it 4-5 fold in the latter.
Overall, however, it appears that the long-term health-re- lated welfare of bitches is likely to be improved, or at least not reduced, by neutering.
Female cats (queens): Neutering prevents the health risks associated with pregnancy, which is more likely to occur in free-roaming cats, compared to bitches. Al- though mammary tumours are much rarer in cats than dogs, they are also much more likely to be malignant, and neutering < 6 months results in a 91% reduction
in the risk of mammary carcinomas7. In contrast to bitches, neutering does not increase the risk of urinary incontinence in queens. The main health related welfare problem for neutered cats (of both sexes) is a substan- tially increased risk of obesity, with neutered cats being signi cantly more likely to become obese than entire cats8, and as a result being at signi cantly greater risk of becoming diabetic. Obesity can to some extent be avoid- ed, however, and so on that basis at least, neutering is likely to improve, or at least not reduce, health-related welfare in queens.
Male Dogs: Surgical complications of neutering are rare, but there are risks of signi cant negative long-term con- sequences for health-related welfare. Castration of male dogs removes the risk of testicular disease and reduces the risk of androgen-dependent diseases such as perine- al hernias. However neutering signi cantly increases the risk of prostate and bladder cancer, and although pros- tate cancer is rare in male dogs (0.2–0.6% incidence), it is almost always malignant9.
Castration also signi cantly increases the risk of lym- phosarcoma, with Hart et al5 reporting a 4% incidence in entire males, compared to 11.5% in neutered males; and Torres de la Riva et al10 reporting that ‘early’ neutered male Golden Retrievers had three times the frequency
of lymphosarcoma of intact males. Similarly, male Rottweilers, neutered at < 1 year of age are four times more likely than intact males to develop osteosarcoma (OSA)6. Thus the costs of routinely neutering male dogs in terms of the increased risk of very serious diseases probably outweigh the bene ts.
Male cats (toms): In contrast to dogs, both testicular and prostatic diseases are rare in toms, thus neuter-
ing has little direct impact on these aspects of health. Some studies report that neutering delays growth plate closure, while others suggest it does not, but none have identi ed a clinical problem as a result. The main wel- fare issue for the tomcat itself is, as with female cats,
a signi cantly increased risk of obesity and of diseases associated with obesity, such as diabetes. Despite this, tomcats are frequently neutered to make them easier to live with by reducing, to variable degrees, urine spraying,
aggression and roaming. Overall, neutering is unlikely to signi cantly affect health-related welfare in toms.
The health effects of neutering vary depending on factors such as the gender, breed, species and age / reproduc- tive stage at which the neutering occurs.
Evidence suggests that, overall, bitches may bene t
from neutering in terms of reducing their risk of serious diseases, but the same is not true of male dogs, where neutering increases long-term health risks. There is less evidence of impact of neutering on the health and welfare of cats.
1. Pollari FL, Bonnett BN, Bamsey SC, Meek AH, Allen DG. Postoperative complications of elective surgeries in dogs and cats determined by examining electronic and paper medical records. Journal of the American Veterinary Medical Association. 1996; 208: 1882-1886.
2. Porters N, Polis I, Moons CPH, Van de Maele I, Ducatelle R, Goethals K, et al. Relationship between age at gonadectomy and health problems in kittens adopted from shelters. Veterinary Record. 27 March 2015; doi: 10.1136/ vr.102678.
3. Hart BL, Hart LA, Thigpen AP, Willits NH. Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Veterinary Medicine and Science. 2016; 2: 191-199.
4. Beauvais W, Cardwell JM, Brodbelt DC. The effect of neutering on the risk of mammary tumours in dogs: a systematic review. Journal of Small Animal Practice 2013; 53: 314-322.
5. Hart BL, Hart LA, Thigpen AP, Willits NH. Long-Term Health Effects of Neutering Dogs: Comparison of Labrador Retrievers with Golden Retrievers. PLoS One. 2014 Jul 14;9(7):e102241. doi: 10.1371/journal.pone.0102241
6. Cooley DM, Beranek BC, Schlittler DL, Glickman NW, Glickman LT, Waters DJ. Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiology, Biomarkers & Prevention. 2002; 11: 1434-1440.
7. Overley B, Shofer FS, Goldschmidt MH, Sherer D, Sorenmo KU. Association between ovarihysterectomy and feline mammary carcinoma. Journal of Veterinary Internal Medicine. 2005; 19 (4): 560-563.
8. Nguyen PG, Dumon HJ, Siliart BS, Martin LJ, Sergheraert R, Biourge VC. Effects of dietary fat and energy on body weight and composition after gonadectomy in cats. American Journal of Veterinary Research. 2004; 65 (12):1708-1713.
9. Bryan JN, Keeler MR, Henry CJ, Bryan ME, Hahn AW, Caldwell CW. A population study of neutering status as a risk factor for canine prostate cancer. The Prostate. 2007; 67 (11): 1174-1181.
10. Torres de la Riva G, Hart BL, Farver TB, Oberbauer AM, Messam LLM, Willits N, et al. Neutering dogs: effects on joint disorders and cancers in Golden Retrievers. PLoS ONE. 2013;

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