Reproduction in the Dog

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Reproduction in the Dog
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Reproductive Tract of the Bitch
Ovary
Oviduct
Uterine Horn
Uterine Body
Cervix
Urethral Opening
Vagina
Constrictor Vestibuli
Clitoris
Fossa Clitoridis
Vulva
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Physiology of the Ovarian Cycle in the Bitch
Puberty
In most bitches begins at 6 to 9 months of
age. Ovarian Cycle in the bitch is monoestrous.
Interval from cycle to cycle varies among breeds
and can be affected by environmental
cues. Range 4 to 13 Months Average 7 Months
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Ovarian Cycle is Divided into Four Stages
A. Proestrus B. Estrus
Physical turgid swelling of vulva and appearance
of a bloody discharge. Vaginal cytology will
change with very early non-cornified
epithelial cells increasing towards end of
proestrus. Behavior - bitch is restless and
secretes pheromones but is aggressively negative
towards male becoming more passive towards start
of estrus
Vulva swelling will soften and discharge will be
slightly pink to straw- colored. Some females
will still have a bloody discharge in
estrus which is normal. Vaginal cytology will
have a high concentration of cornified
epithelial cells with little debris. Behavior -
bitch seeks male turns hindquarters towards him,
raises pelvic region, waves tail to one side and
finally stands for mating by male.
Wolf Heat - (split heat) Have apparently normal
heat but go out of heat without ovulation.
Followed by another heat 2-6 weeks later (Fertile
Heat)
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C. Metestrus D. Anestrus Pseudopregnancy
Loss of vulva swelling and no discharge. Vaginal
cytology is no cornified cells and high numbers
of White Blood Cells. Behavior - non-acceptance
of male
Period of ovarian inactivity and no vaginal
discharge Will not return to heat again until at
least 4 months
Extension of metestrus period in which
progesterone concentrations remain elevated.
Female will have nest building behavior and
enlarged mammary glands.
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Endocrinology of the Estrous Cycle in the Bitch
Higher Brain Centers
Hypothalamus
GnRH
Anterior Pituitary
LH
FSH
Ovary
Estrogen
Progesterone
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Changes During Estrus of Bitch
Vulva Swollen and Enlarged
Bloody discharge from vulva
Copulation
Aggressive towards Male
Passive
Provides sexual posturing to male for copulation
Proestrus Estrus
-8 -4 0
4 8 12
Indicates Day of Peak in LH
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Hormonal Patterns During Estrous Cycle of Bitch
Fertile Period
Fertilization
Ovulation
Estrogen
Completion of Meiosis I
Arbitrary Plasma Concentrations
Progesterone
LH
-10 -6 -4 -2 0 2 4 8 12
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Days from LH Peak
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Ovulation Fertilization
Ova are released from the follicles approximately
two to three days following initiation of LH
surge.
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.
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B. LH Peak C. Plasma Progesterone
The greatest number of ovulations occur 24 to 72
hours after the LH peak. Breeding can be timed
from the LH Peak to the fertile period 4 to 7
days later.
Plasma progesterone concentrations rise prior to
ovulation in the bitch. This occurs because
follicles will start luteinization before
ovulation. Measurement of serum
progesterone concentration can be used as a means
to determine day of ovulation and breeding but
concentrations can be highly variable and the
following are only guidelines.
Baseline Progesterone 1 ng/ml Day Preceding
Ovulation 3-4 ng/ml Day of Ovulation 4-8 ng/ml
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Hormone Concentrations During Pregnancy and
Parturition
Parturition
Mating
Prolactin
Progesterone
Corticosteroids
Arbitrary Plasma Concentrations
Total Estrogens
0 10 20 30 40
50 60 70 Days of
Pregnancy
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Breeding
Dog achieves intromission by vigorous thrusting
of the hindquarters . The bulbus glandis swells
(6X4 cm) in the vagina in which vulva sphincter
muscles contract around the penis forming the
copulatory tie.
First Stage of Coitus
The Turn
Second Stage of Coitus
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Signs of Impending Parturition
Behavior of bitch is one of nest building,
restlessness and seeking quiet, out of sight
areas. Vulva becomes swollen, edematous and may
have some vaginal discharge. Relaxation of pelvic
and abdominal muscles is a consistent sign of
impending parturition. Presence of milk in
mammary gland is not an accurate sign. Decrease
in body temperature from 38 to 37oC just
before parturition.
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Parturition
First Stage of Labor
Averages 4 hours but can last 6-12 hours Period
in which the cervix dilates Bitch will be uneasy,
refuse food, pant, vomiting and frequently
looking at flank. Visible straining of bitch in
the sitting position and back against the box.
Placental membrane will break and there will be
fluid discharge from vulva. Amnion covering the
pup will be visible as it passes through the
cervix, vagina and out the vulva. Membrane will
rupture spontaneously or through licking of
dam. After the start of labor (active
contractions) first fetus cannot be expected to
survive more than 6 hours in the uterus. Fetuses
should be delivered within 2 hours of each other.
Usually interval between puppies is about 30
minutes.
Second State of Labor
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Third Stage of Labor
Passage of fetal membranes should take 5 to 15
minutes.
Dystocia Definition Any problem with delaying
normal birth of fetus.
Symptoms Abnormal fetal presentation, position
or posture Strong and persistent labor for 20
minutes without delivery of fetus. Weak and
infrequent contractions for 2 to 3 hours More
than 4 hours from delivery of last fetus (if not
last one) Most common problem is uterine inertia
(weak contractions), size of fetus and birth
canal.