Pregnancy and Parturition

Pregnancy begins with

• Fertilization – the union of sperm and ovum

• Creates a zygote

24 hours

• Zona locks out all other sperm

• Sperm DNA and egg DNA combine

• Cell divides

8 celled pig zygotes

Day 5

• Arrive in the uterus

• About 100 cells

• Called a blastisist

Day 6

• Break out of Zona

• Suppresses Mother’s immune system in the uterus

• Attaches to uterine wall

• Begin to form placenta

• Placenta is the membrane that surrounds and supports the embryo inside the uterus

Week 2

• Blastisist is the size of a poppy seed

• Gasterlation begins – forms 3 layers of cells– lungs, liver, digestion– heart, muscles, bones, blood– central nervous system, skin, hair

• Embryo

Week 3

• Form a neural tube

• Brain begins to form

• Blood vessels connect

• Heart begins to beat

• Backbone begins to form

Week 4

• Arm buds develop

• Backbone curls into a tail

• 1/5 inch long

Week 5

• Retina and lens form

• Ear begins to form

• 1/4 inch long

Growth of Embryo

• Week 6 - 5/8 inch long

• Week 7 - 3/4 inch long

• Week 8 - 1 inch long

• Week 9 - 1 1/2 inch long

• Week 12 - 3 inches long

• Week 16 - 5 inches long

Milestones of the embryo

• Month 4 - Hard bone begins to form

• Month 5 - Fetus can hear sound

• Month 7 - Fetus begins to lay down fat deposits under skin and in brain

Gestation

• period of pregnancy

• Lengths of Gestation in livestock

Cow 285 days

Sow 114 days

Mare 336 days

Ewe 147 day

Parturition

• birth of the fetus

• Begins with the release of cortisol

• Cervix relaxes and dilates

• Oxytocin and estrogen are released to begin labor and milk production

Parturition (cont)

• Contractions of the uterus push the fetus through the cervix and down the birth canal out in to the world

• Fetus must fine the path of least resistance through the pelvic bones

• The normal presentation for lambs, calves, and foals is front feet first with the head tucked between

Problems

• Wrong presentation of fetus

• Too small pelvic area

• Too large fetus

• Placenta does not break

• Mother does not come to milk

After Parturition

• Afterbirth – the uterus releases the placenta, and it passes out shortly after the fetus is born. ** Retained placenta

• Lactation – mother making milk for baby

• Colostrum – mother’s first milk that contains antibodies for the baby; foals die without it, so horse breeders milk mares and freeze it.

28 day pig embryo