Globally, the approach to neutering of dogs varies considerably. Although surgical neutering is considered part of responsible pet ownership in the UK (similar to vaccinations) and performed routinely across the country, in Germany and Scandinavia, for example, surgical neutering is considered “mutilation” and is prohibited by law. Britain has one of the highest neutering rates in the world when it comes to canines, with over 80 percent of both males and females seen in veterinary practices having been surgically neutered. In the US, early neutering at eight weeks is common, whereas in northern European countries surgical removal of gonads is considered mutilation and is regulated by Animal Welfare Acts, just like docking in this country. This article will try to describe neutering as it is practised today in the UK, followed by articles discussing practices in other countries.
Practice policy
Most practices in the UK recommend neutering both male and female canines between six months and two years of age. There is a tendency for earlier and higher neutering rates of both sexes in urban practices and many rural practices will still recommend letting the female have a season before ovariohysterectomy (OHE) is performed. Veterinary practices usually have a set policy that is recommended to the clients by all members of staff. Neutering of both males and especially females is regarded as responsible pet ownership with many future health benefits for the neutered animal. It is rarely mentioned that neutering involves elective surgery on a healthy animal.
Advantages of neutering females
- Neutering a bitch before her first season will reduce the incidence of mammary tumours greatly. The use of non-surgical contraceptives is not as safe and increases the risk of developing these tumours.
- Prevention of unwanted pregnancies and control of dog population.
- Prevention of uterine and ovarian disease and neoplasia.
- Prevention of “in season bitches” living in pet homes.
- Prevention of behavioural alterations due to pseudopregnancy.
- Behaviour modification may be favourable for some animals of both sexes.
Oestrogen is one of the primary causes of canine mammary cancer, the most common malignant tumour in female dogs. Animals that are spayed prior to one year of age very rarely develop this malignancy which is very common in entire females. More than 50 percent of females that are left entire will develop mammary tumours in their life. The highest relative risk of mammary tumours was found in Boxers, Cocker Spaniels, English Springer Spaniels and Dachshunds (Moe, 2001). Recent studies on the incidence of pyometra are hard to come by with many countries routinely neutering all non-breeding females. The incidence observed in a colony of beagle bitches more than four years old over a 12-year period in Japan, was 15.2 percent (n = 165), with the average age of onset 9.36 +/- 0.38 years. (Fukuda, 2001).
Advantages of neutering males
- Prevention of testicular and prostatic disease and neoplasia.
- Prevention of roaming and some forms of aggression.
- Prevention or reduction of marking behaviour.
In the dog, the obvious advantage is the decreased risk of prostatic disease, including benign prostatic hyperplasia, prostatitis, prostatic cysts and squamous cell carcinoma of the prostate. Testicular neoplasias, the second most common cancer in intact dogs, are also eliminated. On the behavioural side, the findings are more ambivalent with territorial aggression decreasing, but a higher incidence of aggression towards other dogs and humans in already “shy” animals (Neilson et al, 1997). Most working dogs (police, sheepdogs, gundogs) are not neutered as handlers feel they are less keen and energetic. Recent development such as deslorelin implants for pharmaceutical neutering and selective receptor treatments for benign prostatic hyperplasia do offer alternatives to surgical castration.
Advantages of intact females and males
The American Society of Theriogenology has recently (2007) published an extensive study on the effects of neutering and has also looked at the numerous positive effects of the sex steroid hormones. Intact animals have a:
- decreased risk of haemangiosarcomas, osteosarcomas, transitional cell carcinomas and adenocarcinomas in bitches and dogs (Cooley et al, 2002);
- decreased incidence of obesity in bitches and dogs, due to a higher metabolic rate;
- decreased incidence of incontinence in bitches;
- lower incidence of chronic vaginitis and perivulvar dermatitis in bitches with juvenile vulvas or juvenile vaginitis if they are allowed to experience at least one oestrous cycle;
- reduced incidence of autoimmune thyroiditis and hypothyroidism in both male and female dogs;
- reduced incidence of cranial cruciate rupture in male and female dogs (Duval et al, 1999), reduced incidence of hip dysplasia in male and female dogs that are not gonadectomised before five months of age.
In addition, aggression towards people and animals may increase in bitches following gonadectomy; and by leaving animals intact there is more chance of retaining an active gene pool for each breed for potential future breeding. The decreased risk of some other cancers does not outweigh the incidence of mammary tumours, uterine and ovarian disease in the female or the prostate and testicular disease in the male. It may, however, be useful in assessing animals of certain breeds which are predisposed for certain types of cancer. In a more recent study, urinary incontinence after neutering occurred in 9.7 percent of bitches. It affected 12.5 percent of bitches that had more than 20kg body weight and only 5.1 percent of bitches that were lighter (<20 kg body weight) (Okkens et al, 1997). The type of surgical procedure (ovariectomy versus ovariohysterectomy) had no influence on the incidence, or on the period between neutering and the occurrence of urinary incontinence. Urinary incontinence occurred on average at two years and 10 months after surgery (Stocklin-Gautschi et al, 2001). In the last years, the Kennel Club has published a list of endangered dog breeds that have less than 50 puppies registered each year. It includes such breeds as the Bloodhound, Manchester Terrier and Clumber Spaniel which would have been quite common until recently. Given that the active breeding life of the female is only about five years and a neutering rate of over 80 percent, extinguishing a breed or narrowing the population to an unsustainable level can happen very quickly.
Alternatives to surgical neutering
Keeping intact females usually involves suppression of oestrus
at certain times in their lives. Traditionally this has been done through administering progesterone either long acting by depot injections (proligestone) or short term with norethisterone.
More recently GNRH agonists such as deslorelin (Suprelorin), which have much fewer side effects, have been used. In many cases, male castration is not necessary and many of the negative behavioural patterns associated with intact dogs can be controlled with proper handling and training. Reversible castrations in males can be achieved by implanting them with deslorelin (Suprelorin), which suppresses the production of testosterone and spermatogenises temporarily.
Conclusion
Although neutering both males and females has certain health benefits, it still involves elective surgery on a healthy animal. This is an approach that is not used in other areas of veterinary medicine and has been rejected as unethical in some parts of Europe. There are advantages to staying intact for both bitches and dogs and these should also be discussed with the owners when making the decision on neutering. There are also many more pharmacological solutions available now for non-surgical neutering as well as the treatment of some of the problems associated with intact canines later in life.
References
Cooley, D. M., Beranek, B. C., Schlittler,D. L. et al (2002) Endogenous gonadal hormone exposure and bone sarcoma risk. Canc Epidem Biomark Prev 11: 1,434-1,440.
Duval, J. M., Budsberg, S. C., Flo, G. L., Sammarco, J. L. (1999) Breed, sex, and body weight as risk factors for rupture of the cranial cruciate ligament in young dogs. J Amer Vet Med Assoc 215: 811-814.
Fukuda, S. (2001) Incidence of pyometra in colony-raised beagle dogs. Experimental Animals 50 (4): 325-329.
Moe, L. (2001) Population-based incidence of mammary tumours in some dog breeds. Journal of Reproduction and Fertility 57 (Suppl): 439-443.
Neilson, J., Eckstein, R. and Hart, B. (1997) Effects of castration on problem behaviours in male dogs with reference to age and duration of behaviour. Journal of the American Veterinary Association 211: 180-182.
Okkens, A. C., Kooistra, H. S. and Nickel, R. F. (1997) Comparison of long-term effects of variectomy versus ovariohysterectomy in bitches. Journal of Reproduction and Fertility 51 (Suppl): 227-231.
Olson, P. N., Kustritz, M. V. and Johnston, S. D. (2001) Early-age neutering of dogs and cats in the United States (a review). Journal Reproduction and Fertility 57 (Suppl): 223- 232.
Stocklin-Gautschi, N. M., Hassig, M., Reichler, I. M., Hubler, M. and Arnold, S. (2001) The relationship of urinary incontinence to early spaying in bitches. Journal of Reproduction and Fertility 57 (Suppl): 233-236.
