Parturition &
Lactation
Animal Breeding
Pensacola Jr College
PARTURITION
Signs of Imminent
Delivery
w Tailhead prominence (due to
pelvic ligaments relaxation)
w Vulval swelling and mucus
strings (by estrogen)
w Behaviors: nesting,
seclusion, etc (by prolactin)
w Enlarged mammary glands
w Calculate gestation period
Camel pelvic
ligaments (72 hours to parturition)
Imminent parturition (ewe)
Mammary swelling
(camel)
Mammary Swelling
(mare)
Parturition
w The birth process, cervical
dialation through placenta delivery:
w Step 1 = cervical dialation
w Step 2 = uterine
contractions / fetal expulsion
w Step 3 = placenta expulsion
1. Cervical
Dilation
w Cervical canal relaxes and
opens
w Relaxin (a protein hormone):
Produced by ovary &
placenta
Relaxes pelvic / cervical
muscles
w Fetus of most animals moves:
Forefeet pointed at cervix
Head between forelegs
Abnormal
positioning
w Breech = tail towards cervix
w One or both feet turned back
w Head turned back
Breech
presentation
One leg
back
Hind legs only
Head back
Both forelegs
back
Elbow lock
Twins - front
and back
Four legs - one
head
2. Fetal expulsion
w Initial trigger = elevated
fetal cortisol
w Cortisol ΰ estrogens produced by placenta ΰ local transfer to uterus ΰ increased PGF2a ΰ local transfer to ovary ΰ CL regression ΰ decreased progesterone
2. Fetal expulsion
(contd)
w PGF2a ΰ small uterine contractions ΰ decreased blood flow to
uterus ΰ anoxia ΰ increased fetal movement ΰ stimulates uterine nerves ΰ oxytocin release from post.
Pituitary ΰ increased contractions (positive feedback loop)
Fetal expulsion
(camel)
Fetal expulsion
(camel)
Dystocia
w Prolonged / difficult birth
w Assistance required
w Due to:
Breech or other problem in
rotation
Twins
Large fetuses
Small pelvic areas
First pregnancy
3. Placental
Expulsion
w Stimulated by:
Secondary oxytocin surge
Low level uterine
contractions
w Retained placenta:
Due to twinning, high milk
production, dystocia, or low vitamin A/E or selenium
Treatment is infusion of
iodine and antibiotic solutions in uterus to prevent infections
Placental
expulsion (camel)
Newborn after
parturition
w Changes in circulation
w Oxygen enters through lungs,
requires surfactant
w Susceptible to temperature
extremes
w Slowly uses glycogen stores
in liver
w Needs colostrum (first milk)
Mother after
parturition
w Reproductive tract returns
to normal:
Organs shrink to normal size
Recovery / repair of uterine
endometrium
w Postpartum anestrus =
absence of cycling
w Postpartum estrus = first
estrus/ovulation after birthing
LACTATION
Mammary Gland
Anatomy
w Udder
w Median and lateral
suspensory ligaments
w Teat:
Teat cistern
Gland cistern
Ducts
Lobes / lobules
Alveoli
Mammary Anatomy
(cow)
Alveolus Anatomy
w Lumen = milk storage area
w Epithelial cells = produce
milk
w Capillaries = bring in vital
nutrients for milk production
w Myoepithelial cells =
contract to cause milk to empty into ducts
Alveolus anatomy
Mammary Gland
Development
w Fetal mammary glands begin
development due to:
Prolactin
Corticosteroids
Progesterone
w Adult female in gestation:
Estrogen ΰ duct development
Progesterone ΰ gland dev
Lactation
w Newborn suckling ΰ release of prolactin (or growth hormone)ΰ milk production
w Young suckling ΰ sensory nerve stimulation ΰ oxytocin from posterior
pituitary ΰ milk letdown (+ feedback)
Inhibition of
Lactation
w Stress ΰ cortisol release ΰ inhibits oxytocin
w Excitement ΰ opiods in brain ΰ inhibits oxytocin
w Either case results in less
or no milk letdown
Milk Composition
w Complete nutrition
including:
Proteins
Carbohydrates
Fats
Water
Minerals
Vitamins
w Composition varies greatly
between species