Reproductive Cycle Of Bitch

Dr. Muhammad AwaisDepartment of Theriogenology

Estrous Cycle Cyclic or recurrent set of physiological and behavioral

changes that takes place from onset of one estrus period

until onset of the next estrus is called estrus cycle.

Interval from cycle to cycle varies among breeds and

can be affected by environmental causes Range: 4 to 13 Months Average: 7 Months

The onset of the first estrous

cycle (puberty) of an

individual bitch is expected

between 6 and 10 month of

age but may not begin until

she has reached 2 years of

age.

STAGES OF ESTROUS CYCLE

Four stages:

1. Proestrus2. Estrus3. Diestrus4. Anestrus

Canine Estrous Cycle

Proestrus

Proestrus lasts from 9 days average.

Estrogen rises from basal anestrous levels (2-10 pg/mL) to

peak levels (50-100 pg/mL) at late proestrus.

Progesterone remains at basal levels (<1ng/mL)

FSH and LH levels are low during most of proestrus, rising

during the preovulatory surge.

Proestrus

During proestrus, the bitch becomes attractive

to male dogs but is still not receptive to

breeding.

Vulvar discharge of uterine origin is present,

and the vulva is mildly enlarged.

The vaginal mucosal folds appear edematous,

pink, and round.

Changes During Estrus of Bitch

-8 -4 0 +4 +8 +12

Proestrus Estrus

Aggressivetowards Male Passive Provides sexual posturing

to male for copulation

Bloody dischargefrom vulva Copulation

Vulva Swollen and Enlarged

Indicates Day of Peak in LH

Estrus

Accept male for matting

Estrus lasts 3 days to 3 weeks, with an average of 9 days.

Estrous behavior precede or follow the LH peak

Primary oocytes ovulate 2 days after the LH peak, and

oocyte maturation is seen 2-3 days later.

the life span of secondary oocytes is 2-3 days.

Ovulation:Ova are released from the follicles approximately two to

three days following initiation of LH surge.

Fertilization: Ovulated ova are not ready for fertilization (must complete

Meiosis I) and therefore are not fertilized until Day 4 to 7

following the LH surge.

-10 -6 -4 -2 0 2 4 8 12 14

Hormonal Patterns During Estrous Cycleof Bitch

Arb

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once

ntra

tions

Days from LH Peak

Estrogen

LH

Progesterone

Ovulation

Fertile Period

Completionof Meiosis I

Fertilization

Diestrus

Bitch becomes refractory to breeding

Diminishing attraction of male dogs.

Vulvar discharge diminishes

Edema slowly resolves.

The appearance of vaginal mucosal folds becomes

flattened and flaccid.

Diestrus

Estrogen levels are variably low

Progesterone levels steadily rise to a peak of

15-80 ng/mL before progressively declining in

late diestrus.

Diestrus usually lasts 2 month in the absence of

pregnancy.

Anestrus Period when female does not experience cycles

Mean levels of FSH are moderately elevated, and those of LH

slightly elevated during anestrus.

Basal LH is low (<1–2 ng/ml) between sporadic, variable-

height and often-large pulses (3–30 ng/ml) at intervals of

7–18 h or longer

Anestrous

At late anestrus, the pulsatile release of LH

increases, causing the proestrous folliculogenesis.

Estrogen levels are basal(2-10 pg/mL)

Progesterone levels (<1 ng/mL) at late anestrus.