Dog and cat overpopulation is a huge problem in the United States today,
with estimates starting at 6 million dogs and cats being euthanized in shelters
alone. This is not including animals that were euthanized by veterinarians
and those that died of other causes. If 2 cats are allowed to produce 8 kittens
per year, they could be the start of 174,760 cats in 7 years! Managing reproduction
consists of either preventing the animal from reproducing by surgical or
non-surgical means, or by careful and responsible breeding.
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Surgical sterilization is the most common method for permanent reproduction
control in dogs and cats in the United States. The most widely available,
convenient and reliable option for reproduction control, surgery can be done
even before the animal is obtained, and is a one-time procedure that lasts
the life of the animal without any further caretaker effort. The most widely
performed procedures are "spays" (usually referring to an ovariohysterectomy
where the ovaries and uterus are removed in females) and "neuters" (where
both testicles are tied and removed from males). These procedures have advantages
and disadvantages that should be weighed by caretakers.
Neutering with removal of the testicles has several advantages in addition to reproductive control. Since the testicles produce the male hormones that control male-specific behaviors, neutering tends to decrease behaviors such are urine marking, mounting other animals, roaming and fighting with other male animals, and removes the more pungent odor of the intact male's urine. It will not change basic personality patterns such as watch-dog barking, hunting activity, playfulness, activity level and seeking affection. One study showed that male intact cats exhibited less affection to humans than neutered cats. By removing the testicles, cancer of the testicles, the second most common tumor in the male unneutered dog, is prevented. Cryptorchid dogs (those that have testicles that never descended into the scrotum so are not visible externally) have a very high risk of cancer if not neutered. Other testicular diseases such as infection or torsion, as well as diseases of the secondary sex organs like the prostate (which will occur in many unneutered males as they age) are prevented.
Rare complications include risks associated with anesthesia and surgical complications, bleeding, scrotal swelling and infection. A common misconception is that after neutering, males will become lethargic and gain weight. No published evidence shows a change in appetite or exercise after neutering. Some possible explanations for the misconception may be the decreased roaming activity and decreased fighting between males. Any weight gain can be controlled by the caretaker decreasing the animal's available food intake. It should also be noted that sperm may still be found in the male for up to 21 days in the dog and up to 49 days in the cat after neutering and may cause pregnancy if allowed to breed.
An alternative to surgical neutering with removal of the testicles is a
vasectomy where the connection between the testicles and the body is tied
off, leaving the testicles in the scrotum. This procedure is not widely performed
because it does not provide the medical benefits such as decreased cancer
risk nor does it affect male-specific behaviors such as intermale aggression
while carrying similar risks to neutering.
By spaying you remove the female's ability to reproduce. Spaying usually involves removal of both the ovaries and uterus in the female. Mammary cancer is the most common tumor of the intact female. If female dogs are spayed prior to their first estrus, risk of this cancer is only 0.5%. But after 1 cycle the risk increases to 8% and after 2 cycles to 26% with not much effect if spayed later than that. So, in order to gain a major medical benefit, the procedure must ideally be done before the first heat cycle. No benefits have been shown by allowing a female to experience her first cycle before spaying.
Spaying also prevents pyometra (infection of the uterus which can be very serious and even fatal), decreases urine marking, prevents cycling behaviors and bloody discharge associate with heat, and avoids disorders associated with pregnancy and birthing.
Although rare, anesthetic and surgical risks (<0.1%) have been reported, including wound opening, infections, bleeding, incomplete removal of ovaries and uterus, and accidental ligation of a ureter. A more common complication is incontinence in dogs (<1%) as they age due to a weakened bladder sphincter which is estrogen sensitive. This problem can be treated pharmaceutically. If food intake is regulated, no weight gain is seen postoperatively. A decrease in activity by some females after spaying has been attributed by some to changes in activity with increasing age, especially since spaying has traditionally been done at about 6 months of age when activity levels often start to decline normally.
As with neutering, there are other surgical options that do not remove
all the uterus or ovaries, but these procedures are not widely performed
due to a lack of health benefits and one is still subjecting the animals
to the same surgical risks.
In the United States, the progesterone hormone, megestrol acetate, is
marketed to suppress estrus ("heat") in dogs. It has been reported to be safe
and effective for this purpose when administered during the appropriate period
of the cycle of the female. To suppress estrus, it has to be given orally
for 8 days, then retreat about every 4-6 months. Some of the adverse effects
seen include weight gain, increased appetite, drinking and urinating more,
diabetes, depression, lethargy, changes in temperament, infections in the
uterus, suppressive effects on immune status, adrenocortical suppression
and hair loss. It is not frequently used in the U.S. due to the repeated
treatments required and the severe side effects possible. It is not currently
approved for use in cats in the United States.
Mibolerone is an androgen hormone that is approved for estrus prevention
in dogs. It is only approved for up to 2 years although it has been shown
to work for up to 5 years of continuous treatment. It is given at least 30
days prior to the expected estrus and is given daily as a liquid added to
food. It has caused vaginal discharge and clitoral enlargement in some dogs
as well as some possible liver toxicity with various doses. It is not currently
approved for use in cats in the United States.
Another method of preventing unwanted litters is to prevent access of your
animal to other breeding animals. Both males and females that are capable
of reproducing should be restricted in their access to other animals. Dogs
and cats do escape from houses and backyards, or other animals may enter
these areas where your animal is kept. Dogs generally come into estrus twice
a year. Estrus is preceded by signs of proestrus, including vulvar swelling
and bleeding, for approximately a week, followed by an estrus with a duration
of 7-10 days. A female dog in heat attracts male dogs giving them strong
hormonal motivation to get to that female, and dogs can mate very quickly.
Cats may cycle at any time of the year, although there tends to be a seasonal
peak of their 21 day cycles in the early spring. They can become preganant
even before weaning a previous litter. If this is the chosen method of reproductive
control, a very diligent owner is needed to closely supervise the animal
and have safeguards to prevent other animals from approaching and mating
Many owners purchasing a new "AKC-registered" or "papered" dog choose to
have their pet reproduce because the dog is a show-quality purebred or in
order to perpetuate outstanding qualities in an animal. AKC registration
or certification means that the ancestors of the dog were all certified to
be of one particular breed and therefore the dog is certified to be of that
breed as well. It does not certify the quality of the dog, nor does it consider
any health problems that may be present in the line. A thorough medical
history as well as history of behavioral traits should be investigated in
both parents and back several generations as genetic diseases often do not
manifest in every generation. Responsible breeders address health issues
and temperament before breeding dogs. Responsible professional bredders believe
that final responsibility for the progeny produced should fall upon the
breeder who produced them and these animals should never be given to shelters.
While non-surgical alternatives are available for diligent caretakers who
can medicate or monitor their animal's whereabouts, surgical sterilization
is currently the most practical and effective method of preventing unwanted
preganancies. Most veterinarians will perform spays when unwanted matings
have already occurred or if a breeding animal has had an accidental breeding.
Some veterinarians offer termination of the pregnancy without spaying. Taking
care of a dog or cat includes taking responsibility for either controlling
the reproduction of your animal or being responsible for any progeny that
your pet produces.
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