Should You Spay Your Dog?

by Teresa Garden, DVM

Spaying a female dog is actually the surgical procedure known as a complete ovariohysterectomy. The ovaries, uterine horns, and uterus are surgically removed, rendering the female effectively “sterilized”. She cannot conceive nor bear offspring and will not come into heat. Recent large research studies performed by the University of California-Berkley and the University of Georgia led scientists to conclude that sterilization not only significantly impacts when companion dogs might die but also as to why.

These studies confirmed many health benefits provided by spaying. Spaying was shown to increase life expectancy by 26.8% compared to intact female dogs. Spaying can protect against mammary cancer which is the most common cancer in intact female dogs. Fifty to sixty percent of mammary tumors are cancerous and can metastasize to the lungs. Spaying before 2 1/2 years old was shown to greatly decrease the risk of developing mammary tumors due to limiting the number of heat cycles.

Spaying will eliminate the possibility of your pet developing pyometra. Pyometra is a life-threatening infection of the uterus. It occurs in 23% of intact female dogs. Four percent of these pets will die from pyometra in spite of emergency medical and surgical treatment. These research studies also showed spaying will decrease the risk of perianal fistulas and will eliminate (the very small) risk of uterine, cervical, and ovarian tumors.

The data gathered during this research project showed there can be adverse effects on health associated with spaying. These findings may help to challenge the “auto-pilot approach” most veterinarians take toward the issue of spaying. The risk of oteosarcoma (bone cancer) needs to be addressed. Spayed dogs have a 2X risk factor for developing osteosarcoma compared to intact females. The findings showed an inverse relationship between time of exposure to sex hormones and the risk of developing bone cancer. Sex hormones are known to influence maintenance of skeletal structure and mass. The risk of osteosarcoma increased with increased breed size and height. Rottweilers spayed at less than 1 year old were 3X more likely to develop osteosarcoma than intact females. This cancer carries a devastating prognosis. A sensible approach to this issue is to avoid early spaying in medium, large, and giant breeds of dogs. Spaying these dogs after they are completely physically mature will decrease the risk of osteosarcoma.

Spayed females have a 2.2 higher risk of developing hemangiosarcoma-a common type of splenic cancer. Breeds at increased risk include Golden Retriever, German Shepherd, Boxer, Boston Terrier, Bulldog, French Bulldog, and Scottish Terrier. Golden Retrievers, Akitas, and Great Danes are at a 3X risk factor of developing hypothyroidism when spayed vs intact females. Spayed female dogs are more likely to be overweight than intact females due to changes in metabolism. The risk factor for obesity is 2X higher in spayed females. This can be offset by feeding a diet reduced in calories.

Urinary incontinence is common in spayed female dogs. The incidence is 20% vs only 0.3% in intact females. This condition requires life-long medication to treat. Urinary tract infections are a likely secondary complication of incontinence. Spaying before 5 1/2 months old increases the risk to urinary tract infections, recessed vulva, vaginal dermatitis, and vaginitis. Consider spaying after females have reached puberty to combat these health ailments.

Various orthopedic disorders are associated with early spaying. Dogs spayed before puberty have a 2X risk factor for cranial cruciate rupture. Early spaying was associated with a 70% increase in age-adjusted risk for hip dysplasia compared to dogs spayed after 5 1/2 months. Spaying causes a 3X higher risk of patellar luxation vs intact females. Spaying was shown to cause a net loss of bone mass in the spine.

The decision when and if to spay your female dog should be made carefully, taking into account age and breed risk factors. This approach emphasizes the importance of treating each pet as an individual case. The data collected from these studies can lead us to believe it is best to spay females only after they become physically mature. Avoiding early spaying in medium, large, and giant breeds of dogs will decrease many of the health-related risk factors discussed above. Health benefits associated with spaying may exceed associated health problems in many cases when a more common sense approach is taken.

Dr. Teresa Garden is chief veterinarian/owner of Animal Health & Healing, a full-service holistic and conventional veterinary practice in the Maplewood/Richmond Heights area. AnimalHealthandHealing.com; phone: 314-781-1738.