NORMAL HEAT CYCLE
A “heat” refers to the time when a female dog becomes sexually responsive to a male dog in attempts to conceive a pregnancy. Most female dogs will demonstrate signs of their first heat sometime after she is 6 months old, with smaller dogs tending to start earlier than larger dogs.
Most dogs will have a heat cycle routinely every 6 to 8 months, with the heat lasting on average a total of 14 to 20 days. During this time frame it is normal to see a bloody vaginal discharge for the first 7 to 10 days. The female may not necessarily ovulate, or release the eggs, until this bleeding subsides. It is during this period when she will typically allow a male dog to breed her.
If successful, a pregnancy will last 60 to 63 days from the mating, although the time will vary depending on when the actual ovulations and fertility occurred.
MONITORING THE HEAT CYCLE
Occasionally, it is necessary to intervene in the natural mating process when natural breeding is unsuccessful. If it appears that the female has a problem conceiving, or if she refuses the male when all else appears normal, several avenues are available.
A series of hormonal blood tests can be done to determine when she is truly ready to ovulate and thus should accept a male. As the female nears ovulation, certain hormones will rise, indicating the timing for insemination.
Examining vaginal cytology is also a helpful tool to map out a cycle. The local cell morphology will mature as the dog nears ovulation.