The Reproductive Cycle
The reproductive cycle commences at puberty and may function throughout the bitch's lifetime as the bitch does not undergo menopause. During her reproductive life, her fertility (or ability to reproduce) peaks at 3 years of age and declines from about 6 years. There are breed and individual variations (often size-related) to this pattern.
The reproductive cycle consists of a number of oestrus cycles each lasting 4 - 8 months. The oestrus cycle is in turn subdivided into 4 stages. These stages are defined in terms of the bitch's sexual behavior. The 4 behavioral stages are, in sequence:
PRO-OESTRUS
Average duration is 5 - 9 days. This stage represents the first obvious evidence of sexual activity. Signs such as a swollen vulva, bloody vaginal discharge and attractiveness to the male are typical.
OESTRUS
Average duration is 6 - 12 days. This stage is characterized by the bitch permitting mating to occur. Ovulation and fertilisation will take place during the course of this stage of reproductive behavior.
DIOESTRUS
Average duration is 2 - 3 months in the non-pregnant bitch. In the pregnant bitch, dioestrus lasts 57 days and ends with the birth of the bitch's litter.
ANOESTRUS
Average duration 3 - 10 months. No obvious signs of sexual behavior are seen. The whelping bitch will produce milk during the first weeks of this stage.
Whelping chart
Bred-Jan 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Mar 5 6 7 8 9 10 111213 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Apr 1 2 3 4
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Bred-Feb 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Due-Apr 5 6 7 8 9 10 111213 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 May 1 2
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Bred-Mar 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-May 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Jun 1 2
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Bred-Apr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Due-Jun 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 July 1 2
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Bred-May 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Jul 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Aug 1 2
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Bred-Jun 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Due-Aug 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Sep 1
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Bred-Jul 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Sep 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Oct 1 2
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Bred-Aug 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Oct 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Nov 1 2
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Bred-Sep 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Due-Nov 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Dec 1 2
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Bred-Oct 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Dec 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Jan 1 2
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Bred-Nov 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Due-Jan 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Feb 1
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Bred-Dec 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Due-Feb 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Mar 1 2 3 4
Inbreeding
Inbreeding is the mating of a pair bearing 50% or more relationship to each other. Examples are parent to offspring, brother to sister, cousin to cousin, grandsire to grand-daughter.
Line-breeding
Line-breeding is the mating of dogs having common distant realatives such as grand or great grand-parents.
Outbreeding
Outbreeding is the mating of dogs that are unrelated or only distantly related.
Outcrossing
Outcrossing is the mating of two dogs two unrelated inbred lines. 
