Rescue Dogs Blog

Association of dopamine- and serotonin-related genes with canine aggression

Balancing Selection on CDH2 May Be Related to the Behavioral Features of the Belgian Malinois

Behavior Genetics of Canine Aggression: Behavioral Phenotyping of Golden Retrievers by Means of an Aggression Test

Differences in Behavior and Activity Associated with a Poly(A) Expansion in the Dopamine Transporter in Belgian Malinois

DRD4 and TH gene polymorphisms are associated with activity, impulsivity and inattention in Siberian Husky dogs

Genetic background of aggressive behaviour in dogs

Heritability Estimates of Behaviors Associated With Hunting in Dogs

Holding back the genes: limitations of research into canine behavioural genetics

Strong selection for behavioural resilience in Australian stock working dogs identified by selective sweep analysis

The genetic contribution to canine personality

The Ontogeny of Expression of Communicative Genes in Coyote–Beagle Hybrids

The complete list of all the papers I have on file can be found here. I update it every so often as I find new things (or as people very kindly contribute articles).

Also, if you have access to it, The Genetics of the Dog 2nd ed. edited by Ostrander and Ruvinsky has a whole chapter on the genetics of behavior and behavioral disorders in dogs, with pages of references to research further. I HIGHLY recommend it to anyone serious about learning canine genetics, it’s a priceless resource.

Socialization. Every dog owner should make sure their dog is properly socialized to other people, babies, other dogs, other animals, cars, trains, etc. But Service Dog handlers take this to another level.

There’s a shopping cart with a broken wheel or two? Excellent, perfect time for training. Oh, the fire alarm went off in a mall? Perfect, let me get my treats. A fake Service Dog is trying to attack mine? Okay, gotta make sure my dog is safe, but if they are, what an awesome training opportunity! Oh, there’s six ambulances speeding by because a building just exploded down the road from us? Let me grab my clicker.

Service Dogs are exposed to every situation imagineable many, many times until it’s all just background noise to them and all they are focused on is helping their handler. 

Overview

The subject of whether and when to spay or neuter our dog and cat companions is decades old, and the dilemma and controversy has not subsided despite intensive medical, scientific and social study. The list of just some of the relevant references at the end of this article attests to the breadth and scope of the existing information.

Some factors that enter into the broader discussion include: • Societal and community responsibilities and concerns • Animal overpopulation and environmental issues • The human-animal bond • Interests and needs of individuals that both want and deplore animal companions • Costs of medical and maintenance care of animal companions • Prevention of cruelty and animal suffering • Personal preferences for eating meat, dairy and fish or only vegetables • Using animals for sport and competition events • Hunting for food and sport

This article will not attempt to address these broader discussion topics, but list them here as food for thought.

Benefits of Spaying and Neutering

For the individual animal and caregiver • Means of permanent birth control. • Less frustration with per caregivers dealing with mating instinct behaviors. • More convenient for the pet caregiver to not worry about estrus soiling of females, unwanted pregnancies, and roaming or sexual aggression of males. Pets more calm and content at home. • Permits early spay and neutering of dogs and cats in pound and shelter facilities (8-16 weeks of age). • Avoids non-compliance (typically above 40%) with pound and shelter sterilization agreement, if completed before adoption. • Reduction in undesirable mating instinct behaviors including mounting and urine spraying, especially problematic in male cats. • Reduced risk of false pregnancies (pseudocyesis) in dogs, which occurs in about 50% of unsprayed females. • Prevention of mammary tumors – female dogs and cats are seven times less likely to get mammary tumors if spayed before their maiden heat cycle. Mammary neoplasia is common in female dogs, with a reported incidence of 3.4%; about 50% are malignant. Female dogs spayed before their first heat have a lifetime chance of developing mammary tumors of about 99.5% less than that of intact females. If spayed after their first heat, the risk is about 92% less. Also, spaying female dogs more than two years before removing mammary tumors increases the survival odds by 45%. • In cats, gonadectomy before 5.5 months of age was not associated with increased rates of death, relinquishment, or occurrence of serious medical or behavioral condition. Provides important long-term benefits, especially for male cats. • Prevention of pyometra, hydrometra, uterine and ovarian cancers, and testicular cancer, although some spayed females may experience pyometra of the uterine stump. • Reduction in prostatitis, prostatic hypertrophy, and prostate cancer.

For the community and society • Reduced pet overpopulation and related cost burden. • Avoid euthanasia of millions of unwanted dogs and cats annually. • Reduced destruction and contamination of environmental rural and urban habitat. • Reduced wildlife interaction and breeding with domesticated dogs and cats. • Reduced feral dog and cat population, cost burden, and potential infectious and zoonotic disease spread. • Reduced cost and emotional burden of unwanted dogs and cats rescued by pounds and shelters. • Reduced non-compliance with pound and shelter sterilization agreement at time of adoption.

Risks and Disadvantages of Spaying and Neutering

For the individual animal and caregiver • Increased anesthetic and surgical complications, especial in the presence of other health issues. The risk for anesthetic-related death with all surgical procedures is low, about 0.05% for healthy dogs and 0.11% for healthy cats. However, this risk for sick dogs and cats is about 1.33% and 1.40%, respectively. • Increased risk of obesity, which varies between dog breeds, but is independent of the age at neutering. Obesity risk in gonadectomized cats is associated with increased food intake. • Increased risk (two-fold) in dogs of either sex for osteosarcoma; the risk increases with increasing breed size and especially dog height. • Increased risk (five-fold in female dogs; 2.4- fold in male dogs) for hemangiosarcoma. • Increased urinary incontinence in adulthood if female puppies spayed before 12 weeks of age. But, spaying at 4-6 months of age did not affect urinary incontinence risk later on. • Increased urinary incontinence in spayed females, with incidence ranging from 4.9-20%. • Increased urinary tract cancers in dogs of both sexes. Increased risk of prostate cancer in dogs (about 2% vs 0.6% in intact males). • Increased incidence of feline lower urinary tract disease, primarily in males. • Increased risk in male cats of stones or a plug in urethra, urethral sphincter incontinence, and urethral blockage. • Increased risk in dogs of both sexes for adverse reactions to vaccinations (27-38% increase). • Parallel increased risk in cats of both sexes for adverse reactions to vaccinations. • Increased frequency of hypothyroidism in dogs, primarily females. • Increased hormone-responsive alopecia (hair loss). • Increased loss of cognitive function in geriatric dogs, especially in males; believed to be associated with testosterone level. • Increased anterior cruciate ligament (ACL) injury and rupture in dogs.

For the community and society (same as above. but the inverse of the beneficial effects)

Behavioral Issues with Spaying and Neutering

• Despite numerous studies, a consensus has not been reached concerning the effects that neutering male and female dogs have on behavior and specifically on aggression. • Study results were highly variable so that other factors presumably have a larger impact than neutering. • For female dogs with existing aggression, many studies have reported increased aggressive behavior to humans and other animals, and some found more separation anxiety. • In neutered male dogs, more behavioral problems were recorded especially in aggression. • In spayed female dogs, the most observed behavioral problem was fearfulness. • Early-age gonadectomy has been associated with an increased incidence of noise phobias and undesirable sexual behaviors in dogs of both sexes. [see more below] • Spaying female dogs reduces production of progesterone, a natural calming hormone and a serotonin promotor.

Breed- and Sex- Associated Differences with Spaying and Neutering

Golden Retrievers vs Labrador Retrievers • Marked increase in three joint disorders (hip dysplasia, ACL tear, and elbow dysplasia) and four cancers (lymphosarcoma, hemangiosarcoma, mast cell tumor, and mammary cancer) was reported in spayed and neutered Golden retrievers than in their intact counterparts. • In male and female Golden Retrievers, with a 5% rate of joint disorders in intact dogs, neutering at 6 months increased the incidence of a joint disorder to 4–5 times that of intact dogs. • In contrast, Labrador Retrievers, where about the same 5 % of intact males and females had one or more joint disorders, neutering at 6 months doubled the incidence of one or more joint disorders in both sexes. • For cancers, in female Golden Retrievers, with a  3% rate of one or more cancers in intact females, neutering at all periods through 8 years of age increased the rate of at least one of the cancers by 3–4 times. • The incidence of one or more cancers in female Labrador Retrievers increased slightly above the same 3% level of intact females with neutering. • However, in male Golden and Labrador Retrievers neutering had relatively minor effects in increasing the occurrence of cancers. Comparisons of cancers in the two breeds suggest that the occurrence of cancers in female Golden Retrievers is a reflection of particular vulnerability to gonadal hormone removal.

Early-Age Spay and Neutering

• Several studies have indicated the procedure to be safe between 8-16 weeks of age, with no increase in mortality or serious health and behavioral problems when compared to conventional age neutering. • One study showed increased incidence of hip dysplasia (6.7%) for dogs neutered before 5.5 months of age compared to 4.7% for dogs neutered later on. • No association between age of neutering and arthritis or long-bone fractures, and no  correlation between age of neutering and musculoskeletal problems. • Study of large breed dogs with ACL rupture found early-age neutering to cause an excessive angle to the tibial plateau. • Female dogs neutered early are much more likely to develop cystitis although the risk did not appear to be chronic. • Two studies showed an increased risk of canine parvovirus infection with early age neuter, but causation was not established. • Separation anxiety, aggression, escape behavior and inappropriate elimination were reduced while noise phobia and sexual behavior was increased. In aggressive males, earlier neutering may increase barking. In cats, asthma, gingivitis, and hyperactivity were decreased, while shyness was increased. In male cats, occurrence of abscesses, aggression toward veterinarians, sexual behaviors, and urine spraying was decreased, but hiding was increased.  

Traditional Surgical Options and Alternatives for Sterilization

• Classical ovario-hysterectomy and castration still considered the traditional methods of spaying and neutering pre- and post-pubertal dogs. The ovaries, fallopian tubes and uterus are removed from a female dog. This sterilizes her and eliminates her heat cycle. • Newer methods include ovariectomy (only ovaries removed) and hysterectomy (only uterus and part of the fallopian tubes are removed).  With hysterectomy, the ovaries remain and produce hormones. • Spaying with laparoscopy is becoming more popular for females. • Tubal ligation by snipping and tying off the fallopian tubes can be performed on female cats and dogs, but few veterinarians perform the procedure. • Castration or orchiectomy is the typical neuter. The testes are removed, and male breeding behaviors should cease. • Vasectomy cuts and ties off the vas deferens, which conducts sperm from the testes. The testes still produce hormones, so that male breeding behavior can continue.  It is uncommonly practiced in dogs and cats.

These alternatives from complete neutering as they leave the levels and cycle of sex hormones unchanged. Both sexes will retain their normal reproductive behavior, and other than birth control, none of the advantages and disadvantages listed above will apply. These methods are favored by those people who seek minimal change in natural state of companion animals and yet still achieve the desired reduction of unwanted births of dogs and cats.

Non-Surgical Sterilization

An approved product available to neuter male dogs; injected into the testes to stop sperm production and render the dog infertile. Because not all of the hormone-producing cells of the testes are affected by the drug, the testis will continue to produce hormones. As research continues, other products for nonsurgical sterilization should be forthcoming.

W. Jean Dodds, DVM Hemopet / NutriScan 11561 Salinaz Avenue Garden Grove, CA 92843

Selected References American Veterinary Medical Association. (2015) Spaying and neutering. https://www.avma.org/public/PetCare/Pages/spay-neuter.aspx.   Retrieved May 22, 2015.

Beauvais W, Cardwell JM, Brodbelt DC. (2012) The effect of neutering on the risk of urinary incontinence in bitches - a systematic review. J Sm Anim Pract  53 (4): 198–204.  doi:10.1111/j.1748-5827.2011.01176.x. PMID 22353203.

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Cave NJ, Backus RC, Marks SL, et al. (2007) Oestradiol, but not genistein, inhibits the rise in food intake following gonadectomy in cats, but genistein is associated with an increase in lean body mass. J Anim Physiol Anim Nutr (Berl) 91 (9–10): 400–10. doi:10.1111/j.1439-0396.2006.00667.x. PMID 17845247.

Cooley DM, Beranek BC, Schlittler DL, et al. (2002) Endogenous gonadal hormone exposure and bone sarcoma risk. Cancer Epidemiol Biomarkers Prev 11(11): 1434–1440. PMID 12433723.

Concannon PW. (1993) Biology of gonadotrophin secretion in adult and prepubertal female dogs. J Reprod Fert Supp 47: 3–27. DeBleser B, Brodbelt DC,Gregory NG, et al. (2009) The association between acquired urinary sphincter mechanism incompetence in bitches and early spaying: A case-control study. The Vet J 187 (1): 42–47.doi:10.1016/j.tvjl.2009.11.004. PMID 20004121.  

Diesel G, Brodbelt D, Laurence C (2010) Survey of veterinary practice policies and opinions on neutering dogs. Vet Rec 166: 455–458.

Egenwall A, Hagman R, Bonnett BN, et al. (2001) Breed risk of pyometra in insured dogs in Sweden. J Vet Int Med  15:530-538.

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Grumbach M. (2000) Estrogen, bone growth and sex: a sea of change in conventional wisdom. J Ped Endocrinol Metab 13: 1439–1455.

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Hart BL, Hart LA, Thigpen AP, Willits NH (2014) Long-term health effects of neutering dogs: comparison of Labrador retrievers with Golden retrievers. PLoS ONE 9(7): e102241. doi:10.1371/journal.pone.0102241.

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Howe LM, Slater MR, Boothe HW, et al. (2000) Long-term outcome of gonadectomy performed at an early age or traditional age in cats. J Am Vet Med Assoc 217 (11): 1661–1665.  doi:10.2460/javma.2000.217.1661. PMID 11110455.

Howe LM, Slater MR, Boothe HW, et al. (2001) Long-term outcome of gonadectomy performed at an early age or traditional age in dogs. J Am Vet Med Assoc 218 (2): 217–21. doi:10.2460/javma.2001.218.217. PMID 11195826.

Lefebvre SL, Yang M, Wang M, et al . (2013) Effect of age at gonadectomy on the probability of  dogs becoming overweight. J Am Vet Med Assoc 243:236–243.

McGreevy PD, Thomson PC, Pride C, et al. (2005) Prevalence of obesity in dogs examined by Australian veterinary practices and the risk factors involved. Vet Rec 156 (22): 695–702.  doi:10.1136/vr.156.22.695.PMID 15923551.

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Neilson J, Eckstein R, Hart B. (1997) Effects on castration on problem behaviors in male dogs with reference to age and duration of behavior. J Am Vet Med Assoc  211 (2): 180–182. PMID 9227747.

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Root-Kustritz  MV. (2007). Determining the optimal age for gonadectomy of dogs and cats. J Am Vet Med Assoc  231 (11): 1665–1675. doi:10.2460/javma.231.11.1665. PMID 18052800

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Sanborn LJ. (2007) Long-term health risks and benefits associated with spay / neuter in dogs. http://www.naiaonline.org/Retrieved 13 April 2010.

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Sorenmo KU,Goldschmidt M, Shofer F, et al. (2003) Immunohistochemical characterization of  canine prostatic carcinoma and correlation with castration status and castration time. Vet Comp Oncol 1 (1): 48–56. doi:10.1046/j.1476-5829.2003.00007.x. PMID 19379330.

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Spain CV, Scarlett JM, Houpt KA. (2004) Long-term risks and benefits of early-age gonadectomy in cats. J Am Vet Med Assoc  224 (3): 372-379. doi:10.2460/javma.2004.224.372. 

Teske E, Naan EC, Van Dijk EM, et al. (2002) Canine prostate carcinoma: epidemiological evidence of an increased risk in castrated dogs. Molecular Cellular Endocrinol 197 (1-2): 251–255.  doi:10.1016/S0303-7207(02)00261-7. PMID 12431819.

Torres de la Riva G, Hart BL, Farver TB, et al. (2013) Neutering dogs: Effects on joint disorders and cancers in golden retrievers. PLOS ONE 2013; 8(2): e55937.  doi:10.1371/journal. pone. 0055937.

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White CR, Hohenhaus AE, Kelsey J, et al. (2011) Cutaneous MCTs: Associations with spay/neuter status, breed, body size, and phylogenetic cluster. J Am Anim Hosp Assoc 47: 210–216.