Physiology of reproduction in bitches

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Physiology of Reproductionin bitch
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Why?

• To know.
• The stages of estrus cycle and
• corresponding clinical signs
• The changes in hormonal profiles
• and physiological changes
• By knowing these, one can intervene successfully
  in the process of reproduction.

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Neonate
Whelping
Puberty
Life cycle of Bitch
Adult
Pregnancy
Oestrous Cycle
Successful Breeding or Mating
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Reproductive Hormones originate from.

• Maternal
• Hypothalamus
• Pituitary Gland
• Ovary
• Placenta
• Fetal
• Adrenal Cortex

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Anatomy of typical mammalian hypothalamus and
pituitary
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HYPOTHALAMUS
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Hypothalamus
Gn RH
OXYTOCIN
For storage
Posterior Pituitary
Anterior Pituitary
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PITUITARY GLAND
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Anterior Pituitary
Posterior Pituitary
Hypothalamus
FSH
Oxytocin
LH
Prolactin
Follicular Devp E2 Prod.
Ovulation P4 prod
?
Uterus
Uterus
OVARY
Mammary gland
Luteal function
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OVARY
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OVARY
E2 E2 E2 / P4
P4
Pregnancy maintenance upto 35 days of LH surge
Estrous behavior
Then who is there to save the fetus after 35th
day ?
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FETUS
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Fetus under stress at end of Gestation
Uterus
Cortisols from fetus to mother
P4 to E2 in mother unit
PGF2a from feto-placental unit unit
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PLACENTA
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PGF2a from feto-placental unit unit
PLACENTA
Pelvis Uterine muscles relaxation
Relaxin
Whelping process
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• Puberty

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Average age of puberty in males and females

• Canine
• Male 5-12 months
• Female 6-24 months

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Puberty in biches has breed variation.

• Small breeds- Earlier
• Large breeds- Later
• Why.

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• Female must reach
• threshold body size before
• puberty can be achieved

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Gn RH neurons detect Moment to-moment changes
inBlood glucose FA
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• Blood FA may stimulate neurons that in-turn
  stimulate GnRH neurons
• Blood FA would be an indicator of nutritional
  status of the animal

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Leptin

• Adipocytes produce leptin that enters the blood.
• Leptin may stimulate GnRH neurons
• Blood leptin reflects the nutritional status of
  the animal because the greater the amount of fat
  the greater the amount of leptin

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Adult
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• Oestrous Cycle

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• Bitches - monoestrus non-seasonal
• Majority show signs of heat within a limited
  season (seasonality)
• Contradiction is probably due to the effect of
  Pheramones
• Pheramones from the fellow estrus bitch can
  induce cycle in an anestrus one
• This influences the intervention of
  pharmacological agents

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Canine Estrous Cycle
Stage Duration in days External signs
Proestrus 9 days Enlarged Vulva w/ bloody discharge, restlessness, no courtship w/ male
Estrus 9 days Clear to pink vulva discharge, female turns hindquarters towards him, raises pelvic region, waves tail, male acceptance and courtship
Diestrus 60 days Vulva shrinks, no discharge, non-acceptance of male, terminates with parturition
Anestrus 100 days Inactive ovaries, no vulval discharge, low steroids
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Swollen vulva sero-sanguinous vulvar discharge
characteristic of proestrus
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Softer vulva tan - coloured discharge
characteristic of Estrus
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• LH surge be taken as a centre point for the
  incidents take place during a cycle

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• Ovulation takes place- 2 days after LH surge
• Maturation ovum-2 days after ovulation
• Implantation of zygote-18-20days from LH surge
• Whelping takes place 63 days from LH surge

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Reproductive cycle in bitch
Prolactin
Fertilization
Ovulation
Implantation
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Changes During Estrus of Bitch
Vulva Swollen and Enlarged
Bloody discharge from vulva
Copulation
Aggressive towards Male
Provides sexual posturing to male for copulation
Passive
Proestrus Estrus
-8 -4 0
4 8 12
Indicates Day of Peak in LH
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FSH LH

• 2-3 weeks prior to proestrus, the ant.pituitary
  secretes FSH in pulses of increasing frequency
• FSH controls the development of the ovarian
  follicles, which in turn secrete principally
  oestrogen, but also, as they reach maturity,
  progesterone.
• Low conc of oestrogen exert ve feedback on the
  ant.pituitary that stimulate more FSH to be
  released, resulting in further follicle growth
  and increased oestrogen concentrations.
• Process continues until the follicles are mature
  about to rupture.
• At this stage, the higher concentrations of
  oestrogen have a -ve feedback effect that inhibit
  FSH secretion and trigger the release of LH from
  the ant.pituitary in a large pulse, which causes
  ovulation

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Ant. Pituitary
LH

• ----------

FSH
E2
E2
E2
Ovary
Oestrous Behav.
P4
P4
Ovulation
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• Successful Mating

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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 14
Days from LH Peak
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• Copulatory Tie is not necessary for conception

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Bitch - unusual in

• Low prog. conc produced by pre-ovulatory
  follicles are present prior to ovulation these,
  in conjunction with falling levels of oestrogen,
  are probably responsible for the initiation of
  standing oestrus
• The signal that marks the end of proestrus the
  beginning of oestrus are progesterone conc. above
  the critical plateau of 0.5ng/ml in conjunction
  with declining oestrogen conc.
• There is a long period of progesterone dominance,
  probably because the canine uterus produces no
  luteolytic factor

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Unique hormonal changes -in oestrous cycle lead
to two distinct phenomena

• False pregnancy cystic endometrial hyperplasia
  (CEH)- pyometra complex
• Long exposure to high progesterone conc. during
  each oestrous cycle may result in a syndrome of
  excessive GH production from the mammary gland
  resulting in acromegaly in some dogs

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• Pregnancy

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• Spermatozoa unite with the matured Ovum and forms
  zygote
• Zygote gets implanted in the uterus at about
  18-20 days after LH surge

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3 stages of Pregnancy

• I.Fertilization to Implantation
• II. Implantation to Ossification
• III. Ossification to whelping

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• Development of CL is initiated in response to LH
  is maintained by luteotrophic
  factor(s)-prolactin
• CL secrete progesterone, which, at high conc has
  a -ve feedback effect on production of LH, which
  maintains these secretory bodies until day 35
• As LH levels dropped down, the P4 levels comes
  down
• Falling levels of progesterone have a ve
  feedback effect on prolactin that maintains
  luteal function after day 35. Prolactin is the
  gonadotrophin secreted from Ant. Pituitary

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Anterior Pituitary
Posterior Pituitary
Hypothalamus
FSH
Oxytocin
LH
Prolactin
Follicular Devp E2 Prod.
Ovulation P4 prod
?
Uterus
Uterus
OVARY
Mammary gland
Luteal function
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OVARY
E2 E2 E2 / P4
P4
Pregnancy maintenance upto 35 days of LH surge
Estrous behavior
Then who is there to save the fetus after 35th
day ?
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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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• Whelping

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• Size of foetus increases
• Pressure on foetus gets elevated
• Pressure causes release of cortisols in fetus
• Cortisols from fetus enters mothers circulation
  through placenta
• Cortisols lead to conversion of P4 to E2 in
  mother
• Cortisols also cause release of PGF2a from
  feto-placental unit
• PGF2a induces production of Relaxin from placenta
• Relaxin results in relaxation of pelvis and
  uterine contractions
• Contractions of uterus will be longitudinal and
  circular movements alternatively

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• These movements push the fetus towards the cervix
• The pressure produced by the entry of fetus at
  cervix stimulates the release of Oxytocin from
  Posterior Pituiary gland
• This Oxytocin further aggravates the uterine
  contractions

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Fetus under stress at end of Gestation
Uterus
Cortisols from fetus to mother
P4 to E2 in mother unit
PGF2a from feto-placental unit unit
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PGF2a from feto-placental unit unit
PLACENTA
Pelvis Uterine muscles relaxation
Relaxin
Whelping process
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Hypothalamus
Gn RH
OXYTOCIN
For storage
Posterior Pituitary
Anterior Pituitary
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• The bitches with single fetus are more prone for
  whelping difficulties than those with multiple
  fetuses.

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Common clinical conditions in bitches

• i. Pre-pubertal-Delayed maturity
• ii. Mature-Mismating
• Pseudopregnancy
• Pyometra
• Prolonged anestrus
• iii. Pregnant-Dystocia
• iv. Postpartum-Agalactia
• v. Ovariectomised-Urinary incontinence
• vi. Ageing-Mammary tumors

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