Controlled Parturition

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Controlled Parturition
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Controlled Parturition

• Synthetic corticoids
• Dexamethasone 20 mg
• Flumathasone 7.5 mg
• Cows responding can be expected to calve between
  34-60 hours post-injection (505 hours).

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• Effects on cow
• Normal birth slight increase in difficulty due
  to lack of complete dilatation and relaxation of
  soft tissue.
• Retention of placenta is very common.
• Popular form of treatment pen- strept.
• No detrimental effect on milk production
• Effects on calf
• Reduction in birth weight

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• Applications are a management tool
• Control time of calving
• Heifer bred to known large offspring producing
  bulls
• Termination of calving period in naturally mated
  herds
• Other uses
• Excessive udder edemas- chronic prolapse of
  vagina- abnormalities of pregnancy

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Parturition

• The physiologic process by which the pregnant
  uterus delivers the fetus and placenta from the
  maternal organism.

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Signs of Parturition (physiological and
behavioral)

• 1. Changes in the pelvic ligaments
• -Soften and relax
• 2. Enlargement and edema of the vulva

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• 3. Mammary activity
• -obvious enlargement of the mammary gland
• -teats become swollen and secretions from the
  teat orifice may be observed
• -Mare colostrum oozes from the teat orifice
  forming a bead of waxing material at the site of
  each teat orifice
• 4. Nest building
• -a feature often observed in polytoccous
  animals behavior may be hindered in intensive
  management systems

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Initiation of Parturition

• Triggered by the fetus involving a complex
  interaction between endocrine, neural and
  mechanical factors (theories on initiation)
• SOW
• corticosteroids- concentrations increase within
  24 hours of parturition and decrease during early
  lactation
• progesterone- levels decline during the last
  days of pregnancy and drop abruptly by day 1
  postpartum

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Some Theories On The Initiation of Parturition

• Theory
• Fall in progesterone concentration
• A rise in estrogen concentration

• Possible Mechanism(s)
• Blocks myometrial contractions during pregnancy
  near term the blocking action of progesterone
  decreases
• Overcomes the progesterone block myometrial
  contractility and/or increases spontaneous
  myometrial contractillity

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Some Theories on the Initiation of Parturition

• Theory
• Increase in uterine volume
• Release of oxytocin

• Possible Mechanism(s)
• Overcomes the effect of progesterone block of
  myometrial contractility
• Leads to contractions in an estrogen-sensitized
  myometrium

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Some Theories on the Initiation of Parturition

• Theory
• Release of prostaglandins (PGF2)
• Activation of fetal hypothalo-pituitary
• -adrenal axis

• Possible Mechanism(s)
• Leads to contractions in an estrogen-sensitized
  myometrium
• Fetal corticosteroids cause a fall in
  progesterone, a rise in estrogen and a release of
  PGF2 these events lead to myometrial
  contractility

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Sow

• prostaglandin PGF2- continual rise until
  parturition and then declining to bacal levels
• estrone- increases to peak levels until day 2
  pre-partum and then falls to basal levels after
  delivery
• estradiol- follows same pattern as estrone

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Sow

• The rise in estrone and estradiol is associated
  with fetal maturity and is primarily of placental
  origin
• The number of fetal adrenal cortical cells
  increase rapidly from day 105 to 113 of
  pregnancy- increasing cortisol secretion

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• Cow and other species are similar to those seen
  in the sow
• Note
• PGF2? in the pig, cattle, and goats has a
  luteolytic (CL dependent) responsibility as well
  as an oxytocic effect in that it causes
  myometrial contractions. Whereas in the sheep
  (placenta dependent) regression of the CL does
  not necessarily need to precede parturition, so
  primary effect of PGF2? is on the myometrium of
  the uterus.

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• Fetal cortisol activates 17a- hydroxylase, an
  enzyme that causes conversion of progesterone to
  estrogen. This elevation is estrogen stimulates
  release of PGF2? and development of oxytocin
  receptors

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Mechanisms of Parturition

• Myometrial contractions
• Estrogen and progesterone influence motility
  through the release of PGF2?
• PGF2? interacts with smooth muscle adenyl cyclase
  causing a decrease in cAMP levels which in turn
  causes contractions
• Dilation of cervix
• 1. May be influenced by estrogen and PGF2?

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• Prostaglandins
• Specifically, PGF2? is the key player involved in
  the events determining the time of parturition in
  all species regardless of whether maintenance of
  pregnancy of CL-dependent or placental-dependent
• -The major site of PGF2? synthesis seems to be
  from the endometrium
• -fetus determines the day maternal determines
  the hour of the day of parturition