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Birth Control For Pets

Is there a birth control pill for pets? 

            I just read an article about a contraceptive vaccine for dogs which was created by veterinary scientists in Chile, where they are looking for an inexpensive option to help control the country’s growing dog population. Before we can talk about contraception in our pets, we need to talk about basic animal reproduction. 

Let’s talk about male pets first.

            Currently the main way to sterilize your male pet (dog or cat) is to surgically neuter him.  Neutering a male pet is quite different than when a man has a vasectomy. When we neuter a dog or a cat, we actually surgically removal the testicles; the remainder of the reproductive tract structures are left intact. Basically, the parts of the male reproductive tract that get removed are those which are responsible for making sperm and, more importantly, the major male hormone, testosterone.

            Some of our human listeners, especially the male ones, may be thinking “why in the world would you do that to your pet?”

  1. Population control; without sperm, dogs and cats cannot father young
  2. Genetic disease control; male pets with genetic disorders (seizures, allergies, orthopedic issues, etc.) cannot pass on their disease conditions to any young if they cannot breed
  3. Many medical disorders can be prevented by neutering; testicular cancer, perianal adenomas, prostate hypertrophy.
  4. Behavioral benefits; neutered dogs are less likely to roam, urinate on objects to mark their territory, hump your pillow and your legs, fight with other dogs, etc. 

Is there any other way to stop your male pet from reproducing without doing surgery?          

            We are going to talk about the sterilization vaccination in a minute, which can be given to both males and females. But until that vaccine is available, the only other thing I can think of would be a product with a hysterical name. It’s called the “Stud Stopper”! 

            The Stud Stopper creates a barrier between female and male dogs when the female is in heat. It is a waistband that is strapped around the male in front of his genitals like a sturdy kind of loincloth with a vinyl back layer (in case of splattering while urinating). The dog is not uncomfortable, but he also can’t mate. The dog can still be himself. He can groom and use the restroom. He doesn’t care that it’s there because it’s not uncomfortable or in his way.

            Stud Stoppers come in five sizes from extra-small to extra-large (for dogs from about 4 to 120 pounds). The product is available in at least eight natural colors from Coffee to Wheat on Amazon and StudStopper.com.

Now, let’s talk about females

When does a female dog first come into "heat"?          

            Puberty or sexual maturity in the female dog usually occurs around six months of age. The smaller breeds may go into estrus or "heat" earlier; the large and giant breeds may be a little older before they come into heat for the first time.

How often do female dogs come into “heat”?

            On average, this occurs about twice a year. Small breeds tend to cycle more regularly than the larger breeds.

How long does a "heat" cycle or estrus last?        

            "Heat” cycles vary, but average cycles last two to three weeks for most dogs. The “heat” cycle begins with the first signs of vulvar swelling or vaginal discharge. It ends when all discharge ceases and the vulva has returned to its normal size.

How can I prevent my female dog from coming into “heat” and having puppies?

There are two methods to prevent estrus or "heat" in a female dog:

  1. Surgery - ovariohysterectomy (spaying)         

            Ovariohysterectomy or spaying involves the surgical removal of the entire female reproductive tract, including the uterus and both ovaries. It is a permanent and irreversible procedure. Although this is a major abdominal surgery involving general anesthesia, there is little risk associated with the procedure when it is performed by a veterinarian.

            When a human woman has a hysterectomy, the ovaries are not usually removed. So, why is it necessary to remove the ovaries in my dog?

            The reproductive cycle of the female dog is entirely different from that of woman. Female dogs come into "season" or "heat" twice a year on average and it is only at that time that they can conceive. The purpose of an ovariohysterectomy is to ensure that the estrus cycle does not occur.

            Spaying has numerous health advantages for dogs.

  1. Preventing certain cancers; it reduces the risk of breast cancer and eliminates the risk of ovarian and uterine cancer.
  2. Unwanted/unplanned litters are prevented
  3. Behavioral changes associated with "heat" cycles are avoided.
  4. False pregnancy; Spaying your female dog will ensure that she does not experience the complications of false pregnancy. False pregnancies mimic true pregnancies and result in abnormal behaviors and increased risk of pyometra (uterine infection) and mastitis (mammary infection).
  5. Pyometra refers to infection of the uterus ("womb"). This is a serious and potentially life-threatening condition in un-spayed females. The risk of pyometra increases with age. Spaying eliminates the risk of this condition.
  6. Breast cancer (mammary neoplasia); Spaying a female dog prior to the first heat cycle reduces her risk of developing breast cancer to less than 0.5%. The earlier a female is spayed, the less risk she has of developing the number one form of cancer in dogs.

  1. Medical control of estrus

            Until the new vaccine is released (in possibly one year), there are currently no approved medications to control the heat cycle in dogs in the United States or Canada. In the European Union countries, there are some medications that are used to prevent pregnancy and regulate estrus. Some of these drugs have a high incidence of serious side effects. 

  • Cheque Drops (Mibolerone) anabolic steroids. Side effects include:

  1. Infertility
  2. Liver damage
  3. Body odor
  4. Personality changes
  5. Weight loss

  • Ovaban (Megestrol acetate); Ovaban works via a different mechanism than Cheque Drops, and is part of a class of drugs known as progestins. Reported side effects include:

  1. Development of pyometra
  2. Mammary gland enlargement and cancers
  3. Diabetes mellitus
  4. Adrenal gland suppression
  5. Behavioral changes
  6. Weight gain
  7. Lethargy
  8. Delayed birth and fetal defects when administered to pregnant animal

            The new contraceptive vaccine from Chile was developed from an existing formula used to sterilize pigs. The vaccine uses the concept of immunologial-sterilization. I’ll explain.

            The vaccine is made of a recombinant protein generated in Escherichia coli. The protein causes anti-bodies to be produced against Gonadotropins. Gonadotropins are produced in the pituitary gland and they are like the pre-cursor to all of the sex hormones. Without gonadotropin, there can be no Progesterone and Estrogen produced in the females and no Testosterone produced in the males. Without these hormones, there won’t be any reproductive activity.

            So technically, it’s immuno-neutering. The effect of the vaccine is similar to that of a surgical castration without needing the resources and subsequent care such an operation requires.

            It can be used in both males and females. Only one dose is needed for the vaccine to take effect. It is also a reversible measure based on hormonal alterations.

            Unlike past attempts to medically sterilize pets (like chemical castration or hormonal birth control, in which the patient would still engage in normal activity but would not be able to fertilize), immuno-castration is more like surgical neutering. There are no hormones so there is no activity. 

            With other hormonal contraceptives (like the ones we humans take) high quantities of hormones induce alterations in the uterus and can be related to the appearance of some cancers. In this case that does not happen. 

            Veterinary scientists hope the vaccine will help to control the growing canine population in Chile, where surgical castration is only applied in small numbers. They expect the vaccine could be administered to a group three or four times greater than those that undergo surgery.

            The vaccine has been patented in Chile, Europe, and the United States, and is undergoing further tests in controlled conditions. In Chile, the final formula will have to be authorized by the Agricultural and Livestock Service, before it is commercialized. 

Now, what about cats? 

            The vaccination is currently being used in dogs only, and not cats, which is a shame since cats are the ones that really have a population growth problem. 

Why is that so? Why are cats such effective reproducers? 

            Cat’s heat cycles are totally different than dogs. They are what are called "seasonally polyestrous." Starting as early as 5 months of age, cats have heat cycles between January through about October. Their cycle is influenced by seasonal changes in the amount of daylight.  Starting around January, a female cat will keep coming back into heat every 7-10 days until she is bred or the amount of daylight decreases (usually around October). To make things worse, cats kept indoors and exposed to artificial lights may cycle year-round.

            So, see the difference? Dogs only come into heat about twice a year, for 2-3 weeks. Cats are in heat pretty much all of the time except when the daylight hours get really short between mid-October to mid-January. Cats have lots more opportunity to get pregnant. And that’s not all; they can get pregnant again before they are even done nursing kittens. 

            For that matter, they can get pregnant again before they are even done heat. Female cats allow more than one tom to mate with her before they come out of heat, so it is possible for a litter of kittens to have different fathers. This is called superfecundation, and it explains whey sometimes there are kittens in the same litter that look completely different. They have different fathers. Actually dogs also have this trait, and that is why some people have purebred papers for dogs that don’t look like anything like their supposed breeds. These are probably from breeding situations where the royal female was mated to the appropriate royal male, allowing the litter to be registered in that royal breed, but then before the female came out of heat, she also mated with another dog in the kennel next door. 

Just a few more interesting notes…

            Symptoms of a cat in heat:  If your cat is in heat, you know it! They assume a posture with her head and front legs near the ground and the rump area held high. They urinate frequently and in odd locations. We have seen clients bring in cats that they thought were spayed when they adopted them at Christmas, then come January they noticed these horrible behaviors.  Just normal heat!  

            Just like in female dogs, spaying your cat will eliminate the risk of certain diseases including ovarian cancers and infections of the uterus, and will greatly decrease the risk of mammary cancer. Also just like in dogs, there have been many options tried for birth control-the Cheque drops and ovarian tablets, but the side effects are the issue. 


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