Normal
reproductive cycle of the bitch
Normal reproductive cycle of the
bitch is comprised of four stages: proestrus, estrus,
diestrus, and anestrus.
- Proestrus
- Average duration: 9 days; range = 3-17 days
Swelling of the vulva, the external tissue of
the vaginal opening, and bloody discharge marks
the beginning of the proestrus stage, also known
as the follicular stage. During proestrus, the
ovarian follicles, each containing ova, increase
in size. Increasing amounts of estrogen hormone,
secreted by the ovarian follicles, cause the
cells of the vaginal walls to take-on a distinctive
shape, a process known as cornification. Both
the level of estrogen and vaginal cornification
are useful indicators of proestrus.
Estrus- Average duration: 9 days; range =3-21 days
Receptivity to mating marks the beginning of
the estrus stage. Physiologically, estrus coincides
with the predominant presence of cornified vaginal
epithelial cells and an increase in serum progesterone
levels to 2 ng/ml. Ovulation usually occurs
2 days following this increase in progesterone
and hence, monitoring the levels of progesterone
is an excellent indicator for timing breeding.
Diestrus- Average duration: 2 months
Approximately 6 days after ovulation, the cornified
vaginal epithelial cells will revert to a non-cornified
state. This condition marks the beginning of
diestrus. This stage ends when progesterone
levels fall to less than 1 ng/ml just prior
to whelping in the pregnant bitch or approximately
2 months after ovulation in the nonpregnant
bitch.
Anestrus- Average duration: 4-4.5 months
The beginning of this stage is marked by the
drop in serum progesterone levels to less than
1 ng/ml. The beginning of proestrual bleeding
marks the end of this stage. Duration of anestrus
is quite variable among bitches and may be governed
by both genetic and environmental variables.
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FCI
Dobermann Standard: