Roles of hormones in parturition and lactation

parturition

giving birth

progesterone (1)

levels decrease - allows other hormones to effect uterine muscles. In some species, this drop depends on the placenta, in others the corpus luteum

oestrogen and oxytocin

levels rise - leads to uterine contractions and cervical softening. Parturition begins

relaxin

secreted by ovaries

relaxes the pelvic ligaments and opens the birth canal

oestrogen and progesterone (2)

levels drop - allowing prolactin to be secreted, triggering lactation

lambing

giving birth in sheep

kidding

giving birth in goats

whelping

giving birth in dogs

calving

giving birth in cattle

what hormone is similar to progesterone?

cortisol

relationship between cortisol and progesterone when giving birth

when animals are stressed their body releases cortisol, which is similar in structure to progesterone

the body prioritises making cortisol, so progesterone levels drop, which causes a high oestrogen:progesterone ratio 

can lead to early labour

lactation

production of milk by the female’s mammary system

allows a mother to provide her offspring with highly nutritious milk to aid its survival

offspring suckles on the mammary system, which stimulates milk release

drinking the milk supports the offspring until they are weaned and ready to move onto other foodstuff

lactation process

nerve impulse caused by: calf suckling, sound of milk machine, sight of calf

prolactin starts the process as it triggers the mammary gland to start milk production

release of oxytocin

mammary system begins to release milk