Chapter 15: Parturition and Postpartum Period

Control of Parturition

Parturition is initiated by the fetus as the fetal hypothalamus matures.

- Corticotropin releasing hormone (CRH)

- Increase in estrogen

- Decreased progesterone

Estrogen increases oxytocin receptors; oxytocin & relaxin stimulate uterine contractions & cervical dilation.

- Mother does not initiate labor; the fetus triggers the whole process

Signs of Impending Parturition

- Udder fills with milk

- Relaxation around tail head/flank

- Nesting

- Isolation

- Off feed

- Colic/Discomfort

Stage 1 of Parturition

Stage 1 = Preparation

- Uterine contractions become regular

- Fetus rotates into position

- Cervix dilates (relaxin & collagenase)

- Pubic symphysis relaxes

Stage 2 of Parturition

Stage 2 = Fetal Expulsion

- Water breaks (chorioallantois ruptures)

- Fetus passes through birth canal

- Amnion ruptures

- Fetus delivered

- Umbilical cord breaks

Stage 3 of Parturition

Stage 3 = Membrane Delivery

- Placenta detaches and is expelled

- Retained placentas are common in ruminants and may occur with premature birth, disease, nutritional imbalance, or twins.

Normal Length of Cow Parturition

Stage 1 = 2-6 hours

Stage 2 = 30-60 minutes

Stage 3 = 6-12 hours

Normal Length of Ewe/Doe Parturition

Stage 1 = 2-6 hours

Stage 2 = 30-120 minutes

Stage 3 = 5-8 hours

Normal Length of Sow Parturition

Stage 1 = 2-12 hours

Stage 2 = 150-180 minutes

Stage 3 = 1-4 hours

Normal Length of Mare Parturition

Stage 1 = 1-4 hours

Stage 2 = 12-30 minutes

Stage 3 = 1 hour

Dystocia

- Difficult Birth

Causes = small dam, first-calf heifers, oversized fetus, genetics, prolonged gestation, fetal malpresentation.

Induction of Parturition in Sow

- PGF2 alpha after day 112

- Before day 110 causes abortion

Induction of Parturition in Ewe

- Glucocorticoids near term

- PGF2 alpha before day 40 causes abortion

Induction of Parturition in Cow

- PGF2 alpha before day 150

- Glucocorticoids after day 150

Induction of Parturition in Mare

- No ideal method

- Near term use oxytocin + PGF2 alpha when appropriate

Postpartum Period

Puerperium = period when uterus returns to normal (uterine involution). Induces decreased uterine size, lochia expulsion, and endometrial repair.

Time for Uterine Involution in Beef Cattle

Full Uterine Involution = 30 days

Ovarian Activity Resuming = 50-60 days

Time for Uterine Involution in Dairy Cattle

Full Uterine Involution = 45-50 days

Ovarian Activity Resuming = 25-40 days (may be longer)

Time for Uterine Involution in Ewe

Full Uterine Involution = 30 days

Ovarian Activity Resuming = 180 days

Time for Uterine Involution in Sow

Full Uterine Involution = 28-30 days

Ovarian Activity Resuming = 7 days

Time for Uterine Involution in Mare

Full Uterine Involution = 21-28 days

Ovarian Activity Resuming = 5-12 days

Factors Affecting Return to Estrus

- Milk sucking intensity

- Nutrition/Negative energy balance

- Parity (first-time mothers take longer)

- Age

- Metabolism

- Season

Cattle Rebreeding Goals

- 1 calf per year

- Gestation is 282 days

- Breed back within 90 days

Ewe/Doe Rebreeding Goals

- 1 lambing per year (or 3 lambings per 2 years)

- Breed within 2 cycles

Mare Rebreeding Goals

- 1 foal per year

- Foal heat at 7-10 days postpartum

Sow Rebreeding Goals

- 24 pigs per sow per year

- Gestation is 114 days

- Wean at 18-21 days