The ASPCA estimates that, of the 5 to 7 million companion animals that enter animal shelters each year, 3 to 4 million are euthanized. Yet, neutering our pets, particularly dogs, remains a hot-button issue. Some claim that neutered dogs lose their masculinity, become obese, and have drastic personality changes. Another argument is that neutering, particularly if done early, will stunt the animal's growth. While there may be physiological drawbacks to neutering in some cases, stunted growth is simply not one of them.
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Traditional Neutering Age
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Until recent years, veterinarians recommended neutering or spaying be done when a dog reached 6 to 8 months of age. Many vets still make this recommendation, as it tends to be one they are comfortable with in terms of anesthesia and surgical practices.
Newer Guidelines
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Other vets, especially in light of pet overpopulation, are now recommending and performing neuter surgeries on younger animals, with the idea being that the surgery be performed before the dog reaches sexual maturity. Although it varies somewhat by breed, dogs become capable of fathering pups well before 6 months of age. Neuters are being performed, particularly on shelter animals, as early as 7 weeks after birth, just before the dog becomes 2 months old.
Effect on Growth
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Reproductive hormones---testosterone and estrogen---play a certain role in canine bone development. Prior to sexual maturity, the growth plates at the ends of immature bones are loosely attached. Once sexually mature, the dog's body releases reproductive hormones, which cause those plates to fuse to the bones. What this means is that a dog neutered prior to sexual maturity---earlier than 4 months or so---actually tends to be slightly larger than one neutered after reaching sexual maturity. The differences are within fractions of inches, but they do exist, as the growth plates fuse to the bones later than in an intact animal. A dog neutered after reaching sexual maturity suffers no loss of growth due to the neutering. It reaches the same potential size it would had it remained intact.
Benefits of Neutering
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Aside from removing your pet's ability to contribute to the dearth of unwanted pets, neutering has health and behavioral benefits for your dog. A neutered animal is less likely to roam, hump, mark territory or be inappropriately aggressive than an intact dog. At the same time, no evidence supports the notion that a neutered animal is more likely to gain weight than an intact one, nor does it lose its natural tendencies to be appropriately protective of its territory and family. In a study cited by Ruth Marrion, DVM, neutered dogs were found to be more active than their sexually intact companions.
Physiologically, spaying and neutering can reduce the risks of certain kinds of cancers and other diseases in dogs. Most notably, ovarian and testicular cancers are nonexistent in animals who are lacking these particular organs. Females are also less likely to develop mammary tumors, which is the most common kind of tumor found in intact bitches.
Potential Drawbacks of Early Neutering
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Because the practice is relatively new, and because there are no set rules in veterinary medicine as to when castration surgery should be performed, there may be potential drawbacks to early neutering. Avoidance of these relies mainly on the surgeon's skill and experience, as well as the individual dog's physiology.
A commonly cited problem in spaying a young female is that she may develop urinary incontinence. This may happen if the muscles of her urinary sphincter are damaged, underdeveloped, or if the nerves in that region are compromised due to the surgery. This may be particularly true for very small breeds.
Chris Zink DVM, PhD, DACVP, states that females who are spayed early are more likely to develop vascular or bone cancers, and that there is evidence that they may develop endocrine disorders later in life. Males who are neutered early may have more incidence of bone cancer. In the case of both genders, Dr. Zink also reports a higher incidence of hip dysplasia in dogs who are neutered prior to sexual maturity.
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