Parturition (in sheep) Flashcards
What is parturition?
- process by which a conceptus is expelled from the uterus
What is the conceptus?
- its the foetus and the placenta
What is the gestation period in the sheep?
*143-147 days
What stimulates parturition?
- a signal from the foetus (foetal stress)
- cervical softening
- co-ordinated myometrial contractions
How many stages are there to labour/parturition?
- 3 stages
What happens prior to the 1st stage of parturition (in the days/weeks leading to it)?
- udder development
- relaxation of pelvic ligaments
- passing of mucous plug from cervix
- vulva swelling
How long can the 1st stage of parturition be?
- 2-6 hrs in sheep
- up to 24hrs in cattle
What happens in the 1st stage?
- regular uterine contractions
- cervical shortening and dilation occurs
- foetus enters birth canal
In the 1st stage there is a cervical dilation - what are the two phases involved?
- latent phase = cervix slowly dilates
- active phase = rapid dilation of cervix
How long is the 2nd stage of parturition?
- 0.5-2 hrs in sheep
- up to 4 hrs in cattle
What happens in the 2nd stage of parturition?
- foetus present at vagina
- abdominal contractions start
- cervix is completely dilated
- rupture of membranes
- complete delivery of foetus
How long is the 3rd stage?
- 5-8 hrs in sheep
- 2-4 hrs in cattle
What happens in the 3rd stage?
- uterine contractions continue and involution begins
- delivery of placenta
What may be signs a lamb was dead before stage 2?
- congenital malformation
- infection
- placental insufficiency
What signs suggest a lamb was dead during stage 2?
- anorexia or trauma
- bradytocia = sloe birthing, dystocia, malpresentation, twins, arthrogryposis
What signs suggest a lamb died after stage 2?
- infection
- hypothermia
- exposure
- trauma
- blood clot in foetal artery
What can loss of progesterone cause?
- induced abortion or initiates parturition
What hormone is essential to maintain pregnancy?
- progesterone
Progesterone is a steroid hormone and therefore is a derivative of what?
- cholesterol
What is the main cause of onset of parturition?
- achieved by foetal stress response
Once the foetus becomes stressed what is released and what increases?
- ACTH is released
- cortisol increases
What axis is involved in foetal stress?
- activation of foetal hypothalamic-pituitary-adrenal axis
What does a rise in foetal cortisol lead to?
- leads to decrease in maternal progesterone
What are the 3 layers of the uterus?
- endometrium
- perimetrium
- myometrium