Knowing when it's the right time to breed your female.....

There are two stages of the heat cycle which are very important for every breeder to know. 
Proestrus
          Proestrus begins with the first appearance of a blood-tinged vaginal discharge and/or vulva swelling and ends with the bitch’s first acceptance of mating.  On the average, proestrus lasts nine days, but the length varies from one or two days.  Males will be attracted to the bitch during proestrus, but she will not allow breeding until her cycle of Estrus. 
Estrus
          Estrus is the period when the bitch will allow mating.  The average duration is nine days, but like proestrus, it can vary from one or two days.  In some rare cases, proestrus can last up to three weeks.  Estrus is also known to some breeders as, “standing heat”, which means she will be receptive to the male’s advances. She may lift her tail, dance in front of the males face. A test is to run your hand down her back, if she is in standing heat, she may lift her tail.  This is also known as flagging, and will be discussed further on this page.
          A good stud will not attempt mate until the correct time when the bitch is ovulating. He senses this by the smell of progesterone the bitch gives off during ovulation. For Smaller breeds, breeding will take place on days 10, 12, 14. Larger breeds may ovulate earlier.  If you are unsure of her best days to breed her, you can take your female to your Vet for a vaginal cytology.
Physical signs of the estrus cycle
          The physical signs that we look for during the bitch’s cycle can be divided into three categories: (1) swelling of the vulva, (2) vaginal discharge, and (3) response of the vulva to touch, “flagging”. 

• Swelling – swelling of the lips of the vulva is stimulated by the rise in estrogens.  Normally swelling of the vulva is detectable at the same time as the blood-tinged vaginal discharge at the
• Beginning of proestrus.  The swelling gradually increases during proestrus and reaches a maximum late in proestrus.  This is when the lips of the vulva are firm, pinkish, and flexible.  Once estrus begins, the vulva area softens, which is a good sign to know when to begin to breeding. 
• Vaginal Discharge – a discharge normally begins at the onset of proestrus, or rather proestrus begins when you first see a discharge.  The amount of blood discharge varies among individual bitches.  Some discharge may be bright red, while some might be light red, pink, amber, or even colorless.
• Flagging – The vulva will become sensitive to touch during estrus.  This sensitivity can be used as a sign of readiness to breed.  During proestrus, if the vulva is touched, there will probably be no response.  As the cycle progresses, this area will become more sensitive, and when stimulated the bitch will flag her tail and the vulva will be elevated to the position needed during mating.  This is a good way to test your female for readiness when the male is not available for testing.

Fertilization
          Once the female ovulates, it will usually take 48 hours for her eggs to ripen before they will allow penetration from the sperm.
Most females will release around 200 eggs which the male may fertilize. Her body and Mother Nature will absorb the unhealthy and some healthy fertilized eggs, leaving fertilized eggs that her body is capable of caring to term. There are some occasions when a female might absorb all of the healthy eggs. This is usually when you might question the stud used in this breeding.  It’s not always the stud’s fault that your female did not get pregnant.

There are a number of reasons a Female may fail to conceive.

• Age – the bitch may be too old or too young

• Poor health

• Irregular heat cycles- it may not be a true heat

• Bred on the wrong days - You may have bred too early or too late
  
• Stud has low sperm count- Always use a proven male that has sired other litters

Wither or not your female encounters a successful breeding, she will then enter into her Diestrus stage. 
          Diestrus is the two month stage following estrus when the reproductive organs are under the influence of progesterone. Diestrus is also the period of pregnancy in a bitch that is successfully bred.  If she is not pregnant, diestrus is the same length of time, about two months.  During this state hormone levels are the same for both pregnant and non-pregnant females.  This is when you have to determine if you are dealing with a real or false pregnancy.  
Interesting Facts:

The female determines how many pups in a litter.

The male determines the sex of the puppies.