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Canine Estrus

Estrus, or heat, is the stage in a female dog'sreproductive cycle during which she becomes receptive to mating with males. At this time, estrogen levels first increase and then sharply decrease, and mature eggs are released from the ovaries. Ideally, your dog should be spayed before she enters her first heat cycle. 
When does a dog experience her first estrus?

First estrus generally occurs when an unspayed female dog is between six and 24 months old. It tends to occur earlier for small-breed dogs and later for large-breed dogs.


How often do dogs go into heat?

Although it varies with different breeds and individual dogs, an unspayed female usually goes into heat twice yearly, about every six months.


How long does a dog stay in heat?

The time during which male dogs are attracted to a female dog is variable, approximately 18 days. However, females are receptive to males for only about half of this time.


How can I tell if my dog is in heat?

During estrus, your female dog may appear nervous, easily distracted and more alert than usual. She may also urinate more often than she normally does. You’ll most probably notice changes in her behavior; this is caused by a shift in her hormone balance. When a female dog is ready to be bred, she may initiate sexual interactions with other dogs, elevate her hind quarters toward males when they approach, deflect her tail to one side and tense her rear legs. At first, vaginal discharge is blood-tinged and the vulva is swollen. When the female is receptive to males, vaginal discharge decreases in amount and is straw-colored.


Successful breeding is really about successful timing. Your dog's heat cycle usually occurs the first time between 6 and 9 months of age; large breed dogs are usually 12 to 18 months old. Do not attempt to breed until your dog is fully mature. The heat cycle, or estrus, lasts about three weeks. It is sometimes difficult to determine the exact day the cycle begins, but you will usually notice her vulva beginning to swell and she may lick herself more than usual. Within a couple of days, you will begin to notice a bloody discharge; however, in small doses, this may not be noticeable. Sometime between the ninth and 12th day, this discharge will become slightly lighter in color. This is when she is fertile and will be willing to accept a male dog. When you introduce the male, he will be very excited and will mount the female. It is important for successful breeding that the dogs form a "tie." A tie occurs when the glands in the penis expand and the vulva contracts joining the two together. This is when the sperm is delivered to the eggs and will last about 15 to 30 minutes. If this breeding was successful, you will have puppies in about 63 days.


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