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September 7, 2011 at 6:00 AM

Veterinary Q&A: Neutering your dog, Part 2

Posted by Neena Pellegrini

crauer.JPGDr. Brad Crauer, above, the medical director of the Seattle Humane Society, and Dr. Jennifer Mills Buchanan, below, a humane society veterinarian, answer this week's questions.


Question: Why are some unaltered male dogs "perfect gentlemen" and do not mark or show signs of dominance or aggression, while others are very difficult to control and train? Can this be breed specific? Age specific? Should environment (or other dogs) be factored in?

Answer: In part, the behaviors associated with intact males (mounting, urine marking, dog aggression) stem from the hormone testosterone, which is the predominant male sex hormone produced in the testes.

Testosterone is the primary hormone responsible for libido in male dogs, and it is this hormone that is behind the urge to mount, announce his presence via urine marking and the inclination to view other dogs as competitors. However, many other factors, including breed, age, socialization, individual tendencies and training play a significant role in a dog's overall disposition.

Breed does influence both desirable and undesirable behaviors. Depending on the intended use of a breed and individual breeding line (field vs. show), a dog may be genetically programmed for specific traits.

For example, terriers were developed for their energy and tenacity in hunting small and potentially dangerous game. As a result, many terriers are focused to the point of stubbornness, which may make them more difficult to train, whether male or female, intact or neutered.

Another factor to consider is age. Most breeds of dogs become sexually mature between 6 to 8 months of age, but psychological maturity may not be attained for up to 3 years. The socialization, training, dog-dog and dog-people interactions during this period of development will influence the ability of an individual dog to overcome his hormonal urges.

Finally, individual variation and experience helps to differentiate the "gentleman" from the rest.

Question: Can you explain the physiology and how behavior is linked to these hormones?

Answer: Many of the inappropriate behaviors associated with unaltered male dogs seem to be a result of rising levels of testosterone at sexual maturity.

Testosterone is produced by the Leydig cells within the testes in response to hormonal signals from the central nervous system, specifically the hypothalamus.

At puberty, the hypothalamus secretes larger and larger pulses of gonadotropin releasing hormone (GnRH), which stimulates the pituitary gland to produce pituitary gonadotrophs, follicle stimulating hormone (FSH) and luteinizing hormone (LH). Both of these hormones circulate throughout the body with myriad effects, but it is LH that stimulates Leydig cells to produce testosterone.

Testosterone is crucial to the formation and maturation of spermatozoa, growth of the prostate gland and maintenance of libido.

In a male intended for breeding, testosterone also stimulates behavioral changes meant to increase his genetic success. The intact male begins to urine mark to advertise his presence to potentially receptive females and prospective rivals.

He will engage in escape behavior, (digging, fence-jumping, roaming) in an attempt find receptive females. He may become protective of females in his home and view other male dogs, neutered or not, as rivals to be removed. And the intact male dog becomes driven to mounting behavior when excited or aroused, often inappropriately.

In addition, training may become difficult at this stage simply because the dog is unable to concentrate beyond his instinctual behaviors. While these behaviors were acceptable in a primitive male, they make it difficult to co-habituate in a human household.

Question: If I have a mature dog, how much change in behavior can I generally expect?

Answer: Neutering won't affect your dog's working abilities, friendliness, playfulness or personality, but some subtle changes may be expected.

Neutering removes the testes, which removes the primary source of testosterone in the body. Therefore, neutering should reduce behaviors associated with high levels of testosterone, such as urine marking, roaming, and mounting. Research shows that castration reduces marking, roaming, and mounting by 50 percent to 90 percent in most dogs.

Unfortunately, not all instances of these inappropriate behaviors are motivated by testosterone. For example, some mounting behavior is part of a normal social dynamic among dogs, and neutered males will continue to participate in social and play behavior.

Researchers also have found that after time, some behaviors become habitual and are not resolved after neutering.

No conclusive evidence has been found that neutering will reduce dog-dog aggression, although it has been postulated that reducing testosterone levels may decrease male-male aggression because the stimulus for rivalry is no longer there. However, in aggression toward human family members, fewer than a third of dogs can be expected to have marked improvement.

The most common change owners note after neutering is weight gain, although this can be easily controlled with diet and exercise. Neutering removes the majority of testosterone and with it a powerful urge to roam. Without the instinct to seek out females, some dogs become more sedentary, but most weight gain is the result of a decreased metabolic need related to age and reproductive status.

Question: Is there a downside to neutering? Is there any reason not to neuter a dog?

Answer: The benefits of neutering far outweigh the potential problems.

Dogs who are neutered before 5 months old have an extended bone growth, which results in taller, thinner dogs. This lengthening of the bones has been linked to an increase in hip dysplasia in those breeds already predisposed.

Question: What do you tell (or advise) clients who think that neutering a dog in some way emasculates or "kills" the natural spirit of the dog?

Answer: A dog's personality and value is too complex to be destroyed by the removal of a single hormone. The personality is built on a combination of genetic traits and individual experience that will remain undamaged by neutering.

Dogs are such wonderful creatures that they do not feel apprehension but live in the moment, and so do not grieve or miss lost opportunities, unlike their human companions. Worry and misgivings about emasculation of a dog is strictly in the perception of the owner.

Drs. Brad Crauer and Jennifer Mills Buchanan

Dr. Crauer joined the Seattle Humane Society in 2010 with 20 years experience as a veterinarian and administrator in private practice and for animal hospital, emergency and shelter facilities. When Hurricane Katrina struck New Orleans, he served as an adviser to FEMA and as the lead veterinarian in charge of rescue, triage, treatment and long-term management of an evacuation shelter. He has two dogs and two Katrina rescue cats.

Dr. Jennifer Mills Buchanan graduated from Oregon State University's College of Veterinary Medicine in 2010. She has been with the Seattle Humane Society for just under a year. She has three cats, a 2-year-old lab and recently adopted Olives, a rabbit with a wheelchair.

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Read our past Q&As:

Veterinary Q&A: Incontinence in dogs
Veterinary Q&A: Hanging tongue syndrome
Veterinary Q&A: Bad breath in dogs
Veterinary Q&A: How much is too much exercise for my dog? Part 2
Veterinary Q&A: How much exercise does my dog need? Part I
Veterinary Q&A: A killer called bloat
Veterinary Q&A: Initial care for new puppies
Veterinary Q&A: Knee problems in dogs
Veterinary Q&A: Flea-control treatment
Veterinary Q&A: Bearded dragon lizards
Veterinary Q&A: Vaccinations for indoor cats
Veterinary Q&A: Lumps and bumps
Veterinary Q&A: More on aging dogs and arthritis
Veterinary Q&A: Aging dogs and arthritis
Veterinary Q&A: Puppy and geriatric exams
Veterinary QA: What dogs can safely chew
Veterinary QA: Why does it cost so much to clean a dog's teeth?
Veterinary QA follow-up: More on cleaning a dog's teeth
Veterinary QA: When to spay or neuter

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Do you have a question about pet health? Ask now! We'll pose some of your questions to a local vet in an upcoming post.

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