6. Physiological parturition of mares - BP!! | Quizlet ZC

Average gestation period of mares

340 days

11 months

How long before parturition should mares be separated

1 month

6-4 weeks before

Colic signs before parturition is expected, may be due to?

Abortion

Where is the most ideal place for foaling

Clean open pasture, away from other livestock

Normal physiological presentation, position & posture (PPP) before parturition

Presentation: anterior longitudinal

Position: dorsal (dorso-sacral)

Posture: complete extension of head & fore limbs

Define parturition

Physiological process in which the pregnancy uterus deliver the fully grown fetus & placenta from the maternal organism on the completion of the normal pregnancy period

Name stages of parturition

1st stage - dilation of brith canal

2nd stage - expulsion of fetus

3rd stage - expulsion of membranes

Typical signs approaching foals

1. Udder becomes distended

2. Oozing of colostrum from teats - waxing

Duration of the 3 stages of parturition

1st stage: 1-4hrs

2nd stage: 0.2-0.5hrs (30 mins)

3rd stage: 1hr (>6/8hrs its retained)

How long is first stage of parturition

1-4hrs

How long does stage 2 of parturition last

20-30 minutes (0.2-0.5hrs)

how long does stage 3 of parturition take

1hrs

After how many hours is the placenta considered retained

>6-8hrs

Characteristic signs of stage 1 dilation of birth canal

Slow regular uterine contractions

Cervical dilation

Rupture of allantochorion

Rotation of fetus (mare & bitch)

When does the fetus rotate in mares

1st stage of parturition

15 minutes before expulsions of fetus

Characteristic signs of stage 2 expulsion of fetus

Stronger uterine & abdominal contractions - very powerful

Maternal recumbency

Appear & rupture of amnion

Expulsion of fetus

Characteristic signs of stage 3 expulsion of fetal membrane

Uterine contraction decrease

Loosening of chorionic villi

Inversion of chorioallanotosis

Expulsion of fetal membranes

Who initiates length of gestation/parturition mare or foals?

Foals decides the day, mares decide the time

What is the primary parturition stimulation molecules in mares

OXYTOCIN!!!!

What is the primary precursors of parturition for: mare, pigs, sheep, cows

Mare: oxytocin

Pig: prostaglandin

Sheep: fetal cortisol

Cow: prostaglandins & fetal cortisol

Physical factors that initiate parturition

1. Increase foal size - uterine irritability

2. Uterine distention - reverse progesterone block, reflex to reduce size by fetal expulsion

3. Fatty degeneration of placenta & presence of infarct - interference of fetal nutritional & separation process of fetus from uterus

Biochemical factors that initiate parturition

1. Increase CO2 tension in material blood bc increase fetal activity

= increase uterine Contractility

2. Release of fetal ag serotonin - release collagenase & stop blood supply to cotyledons

Fetal Neuroendocrine factors initiating parturition

1. Increase cortisol in adrenal - convert P4 to E2 & release PG

2. Increase ACTH of pit - stim cortisol release

3. Increase CRH in hypo - stimulate ACTH

4. Increase endogenous opiods - stim ATCH secretion

Maternal neuroendocrine factors initiating parturition

1. Reversals of progesterone block - myometrial contractions

2. Release of relaxin - dilation of birth canal, pubic symphysis & sacro sciatic lig

3. Placental estrogens rise - release of PG in Contractility

4. Pro inflam cytokine - softening of cervix

5. Release of PG - stimualte sm contraction

What two mechanical process is successful parturition dependent on

1. Ability of uterus to contract

2. Capacity of cervix to dilate

Involves a lot of changes to maternal & fetal systems

List maternal changes that occur in parturition

1. Myometrium

- slow infrequent contracts with little hydrostatic pressure

2. Cervix

- dilation induced by maternal steroids, prostaglandin, relaxin & pro-inflam cytokines

- softening / ripening involves edema & enzymes

3. Mamary glands

- large increase in BF

- change in volume

- secretion

Main compounds for inducing of mares parturition

1. Exogenous glucocorticoid - limited effeicny

2. Prostaglandins

3. Oxytocin IV

Main method of inducing parturition in mares

Oxytoxin IV (also dogs)

Result of oxytoxin injection in inducing parturition

Causes:

1. Myometrial contraction

2. Abdominal contractions

3. Expulsion of fetus

Mechanism of steroidogenesis between mare & fetus

Mother provide cholesterol precursor

In CL it s converted to pregnenolone, then progesterone

Fetus converts progesterone -> dihydroandrosterone

Placenta converts dihydroandrosterone to estradiol

Cortisol produced by the fetus, convert to aromatising enzymes in placenta & has negative effect of conversion of dihydroandrosterone to estradiol i.e., production of androgens

List hormones related to parturition

1. Estrogen

2. Relaxin

3. Prostaglandins

4. Oxytocin

5. Glucocorticoids

Function of estrogen in parturition

1. Increase synthesis of contraction associated proteins in myometrial cells

2. Increase electrical coupling by activation of connexin-43

3. Increase expression of PG & oxytocin receptors

4. Increase release of prostaglandins

Function of relaxin in parturition

Causes widening of pelvic by relaxing sacro-sciatic ligament & public symphysis of pelvic girdle

Function of prostaglandin in parturition

Increases contraction during labour in all species

Function of oxytoxin in parturition **

1. Power contraction of myometrium

2. Changes estogen: progesterone ration

3. Increase PG production to increase oxytocin receptor formation

Function of glucocorticoids in parturition

Cortisol - enhances amnionic cyclooxygenase & inhibits chorionic prostaglandins dehydrogenase activity

Name hormone responsible for widening of pelvis, relaxing of scars-sciatic ligament

Relaxin

What causes the increased expression of PG & oxytocin receptors on uterus

Estrogen

Function of fetal cortisol

Convert P4 to E2 & release PG