Transcript Maternal Response to Pregnancy Parturition

MATERNAL RESPONSE TO
PREGNANCY, PARTURITION
AND NEONTATAL TRANSITION
TO EXTRA-UTERINE LIFE
ANSC 631
BAZER
MATERNAL RESPONSE TO
PREGNANCY: GENERAL
TIRED
SLEEPY
CARDIOVASCULAR ISSUES
APPETITE
MAMMARY DEVELOPMENT
CHANGE IN LIBIDO
NAUSEAU AND VOMITING
• 4 to 6 weeks to 14-16 weeks of pregnancy
• Hyperemesis gravidarum severe nausea,
vomiting, weight loss, and sometimes
electrolyte disturbance, may require
hospitalization for intravenous fluid and
nutrition.
• Why
– Ho: adding spices to food inhibits growth of
microorganisms and protects from diseases
– expelling or avoiding foods during early months of
pregnancy protects mother and embryo from
foodborne illnesses and toxins, especially when the
fetal development is most sensitive to disruption.
American Scientist
89 (2):142
Protecting Ourselves from Food: Spices and morning
sickness may shield us from toxins and microorganisms in
the diet. Paul W. Sherman, Samuel M. Flaxman
SPECULATION
•Progesterone is analgesic with LD50 that may cause nausea by
acting on nervous system like an anesthetic
•Changes in gut immune system response to food allergens, e.g.,
like some people respond to peanuts or shell fish
REVIEW OF DIGESTION
• STOMACH
– HCl, PEPSIN, RENIN AND GASTRIC LIPASE
START PROCESS
• SMALL INTESTINE
– ENZYMES TRYPSIN, CHYMOTRIPSIN, ETC
DIGEST PROTEINS
– PROTEIN SOLUBILITY AND DIGESTIBILITY
– AMINO ACIDS ABSORBED
– CHYLE TO LACTEALS (LYMPH VESSELS) FOR
SURVEILLANCE
• LARGE INTESTINE
– ABSORPS WATER AND SALTS
Maternal nutrition and fetal development. J Nutr. 2004 134:2169-2172 Wu G,
Bazer FW, Cudd TA, Meininger CJ, Spencer TE.
Nutrition: intrauterine environmental factor altering expression of fetal genome
with lifelong consequences ("fetal programming”) and "fetal origins of adult
disease."
1) change structure, physiology, and metabolism of offspring predisposing
individuals to metabolic, endocrine, and cardiovascular diseases as adults;
2) maternal undernutrition and overnutrition reduce placental-fetal blood flows and
stunt fetal growth.
3) impaired placental NO (vasodilator/angiogenesis) and polyamines (DNA and
protein synthesis) result in intrauterine growth retardation;
4) nutritional status alters epigenetic state through DNA methylation and histone
modifications of fetal genome thereby impacting fetal programming and genomic
imprinting.
MATERNAL CARDIOVASCULAR
SYSTEM
• 10-15% decrease in systemic arterial blood
pressure
– Decreased vascular tone: systemic vascular
resistance =
mean arterial pressure
cardiac output
PGE2, NO, PGI2 and decrease in alpha
adrenergic receptor leads to vasodilation
and decrease in mean arterial pressure
MATERNAL CARDIOVASCULAR
SYSTEM
• 25 to 60% increase in cardiac output
– Increase mostly after mid-gestation
– Cardiac output = heart rate X stroke volume
• Heart rate increase by 20 to 30%
• Stroke volume increase by 30-35%
• Increases in:
– Left Ventricle Mass
– Left Atrial Size
– End-Diastolic Dimensions
– Blood Volume Increase by 10 to 50%
– Highest percentages with multiple fetal-placental units
MATERNAL CARDIOVASCULAR
SYSTEM
• Red Blood Cell Mass (Hematocrit)
– Increases less than blood volume
– Increase in erythropoietin and erythropoiesis
– Physiologic Anemia of Pregnancy
• Blood Volume – Plasma Volume = Red Blood Cell Mass
• Vascular Reactivity Decreases
– Increased metabolic clearance of vasoactive agents
such as norepinephrine and angiotensin II
– Decrease in alpha adrenergic receptors
– Increase in vasodilators – PGE2, PGI2, NO
MATERNAL CARDIOVASCULAR
SYSTEM
• Distribution of Cardiac Output
– Sheep – 3 to 4 Liters/min
• Uterus – 0.8 to 1.2 L/min
• Uteroplacental Blood Flow (Percent of Cardiac
Output
– Ewe: 8% at mid-gestation; 16% in late gestation;
and 0.06% for nonpregnant uterus.
– Women: 17% at term
• Mammary Blood Flow: Increases from 0.2% in
first trimester to 2% at term
• Skin Blood Flow – 100% increase over course
of gestation
MATERNAL PULMONARY SYSTEM
•
•
•
•
Increased respiratory rate
Increase in tidal volume
Decrease in arterial pCO2
Increase in chest circumferance – 5-7 cm
in women
• Decrease in bronchial/alveolar resistance
MATERNAL BLOOD COAGULATION INCREASES
FROM 3 MONTHS TO TERM
• Increased fibrinolytic cascade
– Venous stasis – thromboemolic events
– Increase in platelet aggregation and
formation of stable fibrin clots
• Intrinsic from Cell Injury and Collagen damage–
increase in events beginning with Clotting Factor
XII to platelet phospholipids and Ca++ to
Fibrinogen and Clotting
• Extrinsic (Rapid from Tissue [placenta]
thromboplastin to go from Clotting Factor VII to
Fibrinogen
– Clotting mechanism increase rapidly at term
MATERNAL METABOLISM
• Cost = 77,000 to 81,000 kilocalories
– 24 year old woman – 56 kg
• Gain 12.5 kg in pregnancy
– 925 g protein
– 3.83 kg fat
– Fetus at term
• 3.44 kg
– 444 g fat
– 543 g protein
MATERNAL METABOLISM
– Pulmonary Ventilation – increases 3 L/min
• 20% increase in maternal O2 absorption into blood
–
–
–
–
–
Pregnant Uterus – 25 ml O2/min
Pulmonary Muscles – 10 ml O2/min
Heart – 9 ml O2/min
Kidneys – 5 ml O2/min
Mammary Glands – 2 ml O2/min
– Increasing Energy Intake Increases Appetite
• Increase of 50 kcal/day first 34 weeks to 300 kcal/day
during last 30 days [basal diet is 2,100 kcal/day]
– Progesterone increases appetite
– Increase in fat increases leptin
MATERNAL METABOLISM
– Poor Nutrition
• Smaller placentae by 20 to 30% and smaller babies by
200 to 300 g in first trimester
– Increase in Nutrient Absorption by 0 to 3%
•
•
•
•
Increased pancreatic/biliary secretions
Increased intestinal blood flow
Decrease in gut motility
Hypertrophy of gut epithelial lining
–
–
–
–
–
–
Increase in villous height
Increase in intestinal dilation
Increase in epthelial hyperplasia
Increase in Vitamin D and Ca++ aborption
Increase in iron aborption
Lactogenic hormones increase absorption of Vitamin D, Ca++
and H2O.
MATERNAL METABOLISM
– Nutritional Priorities of Fetus and Mother
• Maternal
– Nervous System
Fetal Demands
Nervous System
Bone
Muscle
Fat
– Bone
– Muscle
– Fat
MATERNAL METABOLISM
– Poor Nutrition
• Smaller placentae by 20 to 30% and smaller babies by
200 to 300 g in first trimester
– Increase in Nutrient Absorption by 0 to 3%
•
•
•
•
Increased pancreatic/biliary secretions
Increased intestinal blood flow
Decrease in gut motility
Hypertrophy of gut epithelial lining
–
–
–
–
–
–
Increase in villous height
Increase in intestinal dilation
Increase in epthelial hyperplasia
Increase in Vitamin D and Ca++ aborption
Increase in iron aborption
Lactogenic hormones increase absorption of Vitamin D, Ca++
and H2O.
MATERNAL METABOLISM
– Physical Activity Decreases
• Progesterone
– Increase in sleep
– Decrease in Anxiety
Mammogenesis and Lactogenesis
• Mammogenesis – Growth of Mammary
Gland
• Lactogenesis
– Stage I – Milk Protein Synthesis
– Stage II – Milk Protein Synthesis and
Secretion
• Galactopoiesis – sustained milk production
MAMMOGENESIS AND LACTOGENESIS
Mammogenesis: Sex Steroid Hormones
Estrogen --Involved in lengthening and branching of ducts
Progesterone --Duct and ductule cell multiplication --Enlargement and/or widening -Actually inhibits mammary growth at high levels
Progesterone + Estrogen -- Causes lobuloalveolar development
Initiation of Lactation (Lactogenesis)
Ovarian and/or placental steroids decrease (Progesterone inhibits)
Placental Lactogen disappears
Lactogenic Complex
Prolactin, Glucocorticoids. Insulin or IGF-I
Milk-Ejection Reflex Oxytocin/Neuroendocrine Reflex
Suckling or other teat/udder stimulation causes release of oxytocin from
neurohypophysis
Maintenance of Lactation (Galactopoesis)
Galactopoetic Complex
Prolactin (Not Cattle), GH, Insulin, Thyroid Hormone, Glucocorticoids
EVENTS PRECEDING PARTURITION
• Final Maturation of Fetus and its HypothalamicPituitary-Adrenal Axis
• Initiation of Milk (Colostrum) Secretion
• Expansion of Birth Canal
• Nest Building (Prolactin)
• Aggression (Prolactin)
• Restlessness (Prolactin and Estrogen)
• Initiation of Uterine Contractions
• Parturition and Termination of Pregnancy
• Bonding Between Dam and Offspring (Prolactin
and Oxytocin)
Fig. 14-14
Fig. 14-13
Fig. 14-15
Parturition in Mammals
• Controlled by fetus
• Congenital absence of Hypothalamic-PituitaryAdrenal Axis
• Ewe consumption of Veratrum californicum on
Days 14-15
– Delayed Parturition
• Lambs up to Day 175 and 20 pounds or more; some
cases ewes died
• Piglets taken at Day 125
• Similar reports for calves taken by C-Section at very
heavy weights, e.g., 200 lb
Parturition – Sheep Model
• Fetus
– Hypothalamus
• CRH
– Anterior Pituitary
• ACTH
• Prolactin
– Adrenal Gland
• Cortisol and Corticosterone
– Placenta
• Progesterone decreasing, estrogen increasing due to C-21 Steroid 17 alpha
hydroxylase enzyme
• Maternal
– Corpus Luteum
• Progesterone and Relaxin (some species)
– Anterior Pituitary
• Prolactin and Growth Hormone
– Posterior Pituitary
• Oxytocin
– Uterus
• PGF2-alpha increasing
Hormonal Factors Associate with
Parturition
• Fetal Hypothalamic-Pituitary-Adrenal Axis
– A. CRH – Day 100 Fetal Life
– B. ACTH – Day 125 Fetal Life
– C. Cortisol Production – Dependent on Critical
Mass of Adrenal Tissue
– D. Cortisol – Increases most rapidly 2 to 3 days
before onset of labor and parturition
– In pigs, adrenal weight increases along with circulating levels of
cortisol most rapidly after Day 100 of the 114 day period of
gestation
Hormonal Factors Associate with
Parturition
• Fetal Hypothalamic-Pituitary-Adrenal Axis
– E. Cortisol
• Stimulates rapid increase in C21 Steroid 17-alpha
hydroylase enzyme for conversion of Progesterone to 17alpha hydroxy Progesterone when then is metabolized to
androgens and estrogens
– P4 DECREASES RAPIDLY DUE TO CONVERSION OF
PROGESTERONE TO ESTROGENS
– Decrease sulfotransferase in endometrium so MORE
UNCONJUGATED ESTROGENS
– Stimulate PGF secretion
Hormonal Factors Associate with
Parturition
• Oxytocin
– Released in response to PGF and due to Ferguson
Reflex of fetal pressure on cervix
– Stimulates uterine contractions
– Stimulates bonding between mother and offspring
Hormonal Factors Associate with
Parturition
• Relaxin
Molecular Weight – 6,300 (6,000 to 10,000)
Pig – From CL
Other species – cow (CL, placenta), sheep (?),
mare (placenta)
Cervical Relaxation
Acts with other hormones:
Estrogens
PGF and PGE
Oxytocin
Hormonal Factors Associate with
Parturition
• Relaxin (continued)
– Increases Keratin SO4 in cervical collagen
– Decreases Dermatin SO4 in cervical collagen
– With loss of Dermatin SO4 there is a decrease in crosslinking among collagen fibers and greater elasticity of
connective tissue of cervix and pelvic ligaments to increase
distinsibility of pelvic canal for birth of fetus
– Role in lactation by stimulating growth and development of
teat and possibly lactation
– Ovariectomized pigs give birth, but don’t lactate normally, so
is relaxin critical to parturition?
Hormonal Factors Associated with Parturition
• Uterine Myometrial Contractions
–
–
–
–
Coordinated and Rhythmic Contractions of Myometrium
Involuntary Contractions of Abdominal Muscles
Dilation and Softening/Distensibility of Cervix
Myometrial Contractions
• Increased synthesis of gap junctions (e.g., Connexin 43) due to
decreasing progesterone and increasing estradiol
Essential for strong coordinated contractions
• Increase in cAMP associated with increase numbers of gap junctions
• Increase in free Ca++ and its binding to calmodulin which activates
myosin kinase:
– Myosin kinase → Myosin-PO4
– Myosin-PO4 + Actin = Contractions
Hormonal Factors Associate with
Parturition
• Uterine Myometrial Contractions (continued)
• Increase in free Ca++ and its binding to calmodulin which
activates myosin kinase:
– Myosin kinase → Myosin-PO4
– Myosin-PO4 + Actin = Contractions
• Oxytocin lowers threshhold potential for action potential of
myometrium and increases rate of Ca++ influx to
stimulate contractions
• PGF increases intracellular free Ca++ and frequency of
contractions
cPLA2
COOH
Phospholipids
Arachidonic Acid
(5, 8, 11, 14-eicosatetraenoic acid)
Cox-1
O
9
7
8
10
O
Cox-2
6
14
11 12 13
Nuclear receptor
4
2
5 3
18
15 16
17
OH
COOH
19
Cox-1
Cox-2
PGI Synthase
TX Synthase
O
O
COOH
COOH
O
O
O
TP receptor
OH
OH
cAMP
OH
PGH2
OH
O
PGD Synthase
PGE Synthase
PGF Synthase
OH
O
COOH
O
OH
PGD2 PGEM
COOH
PGDH OH
Ca2+ + IP3
TxA2
PGI2
DP receptor
cAMP
20
PGG2
PPAR
PPAR
PPAR
IP receptor
COOH
COOH
OH
PGE2
Inhibited at Parturition
9-keto-PGE
reductase
OH
Ca2+ + IP3
OH
PGF2
FPA,B receptor
PGDH
PGFM
Inhibited at Parturition
Constrictor Receptors
Relaxant Receptors
cAMP
EP1
EP2
EP3a
EP3b
EP3c
EP3d
EP4
Ca2+/IP3
cAMP
cAMP
cAMP
cAMP
cAMP/
cAMP
IP3
Ca2+ / IP3 or cAMP
11β
hydroxylase
11β hydroxylase for corticosterone
and cortisol
Ovine
Human
Fetal Hypothalamic Pituitary
Adrenal Axis
↓
Placental ←
Estrogens
Fetal Glucocorticoid Production
Corticosterone and Cortisol
↓
Intrauterine
Production of Prostaglandins
→ Placental CRH
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
CRH is Produced by Human Chorion in response to
cortisol from fetal adrenal
CRH stimulates Dehydroepianrosterone Sulfate
(DHAS) from fetal adrenal that is converted to
estrogens by chorion
Glucocorticoids and estrogens stimulate increased
expression of prostaglandins E and F and decreases
PGDF-15 that OTHERWISE inactivates PGs
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
Central Characteristics of Human Parturition
Increase in CRH and PGHS2 in chorion
Decrease in PGDH15
Increase in FP and EP prostaglandin
receptors
Decreased sensitivity of uterus to
progesterone
Increase in production of estrogens from
DHAS by chorion
Increase in myometrial contractions
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
Conversion of Progesterone to Estradiol and Loss of
Progesterone Influence
Increased Contraction Associated Proteins
Oxytocin Receptor
PGF Receptor
Connexion-43 Gap Junction Protein
Recent Suggestion that Increase in Progesterone
Receptor C Isoform Results in Loss of Progesterone
Responsiveness via PR Isoforms A and B in Human
Myometrium (Condon et al. 2006 Mol Endocrinol
20:764-775
Controlling Time of Parturition
• Efficient use of labor and facilities to
reduce neonatal death losses
• Reduce length of gestation
• Increase opportunities for cross-fostering
neonates in event of failure of dam to
accept offspring, cannabilism or failure to
lactate
• Convenience of producer
• In swine, uniformity of post-weaning estrus
Controlling Time of Parturition (continued)
• Swine: Corticoids Ineffective
– PGF-2 alpha – 200 ug cloprostenol or 10 mg Lutalyse at 7
AM and 7 PM with farrowing 24-26 h later.
– Should not be used prior to Day 112 of pregnancy due to
decreased survival of neonate
• Cows; Corticoids, Estradiol and PGF are effective
– 20 mg dexamethasone to dam most commonly used. For
maximal survival of calf, cows should be within 1 week of
term. Some countries with wet and dry season induce
parturition to coincide with rainy season, high nutrient
availability and focus on milk production with calves having
little economic value
• Retained placentae major issue
Controlling Time of Parturition (continued)
• Mare: Corticoids, PGF and Oxytocin
– 2.5 mg PGF (Lutalyse) every 12 hours causes
birth/abortion in late gestation.
– 200 dexamethasone/day for 4 days with foals being
born 72 to 96 h after end of treatment
– 20 IU to 200 IU Oxytocin administered with estradiol
will cause cervical dilation and birth in some cases.
Post-Partum Period
• Cow
– Days 0-12 – Sloughing and Discharge of
endometrial tissue and placenta
– Days 25-30 – Uterine Involution completed
– Days 40-45 – Uterus considered ready for
next pregnancy
– Dairy – First estrus around Day 15 to 20 and
breeding from Day 60
– Beef – First estrus between 60 and 100 days
and breed during desired dates (spring or fall)
Post-Partum Period
• Sheep
– Uterus involuted by Days 25 to 30
• Breed in fall
• Pig
– Uterine involution completed by Days 21 to 28
– Breed at post-weaning estrus (3-7 days)
• Mare
Foal Heat – 5-15 days postpartum
Breed if no complications
Human
Highly variable and related to many factors
Suckling intensity, body condition, nutrition etc
Fetal to Neonatal Transition
Adjusting to Extra-Uterine Life
Fig. 14-14
Fig. 14-13
Fig. 14-15
Cardiovascular Function
• Ductus Arteriosis – Duct between Pulmonary
Artery and Aorta that allows most blood to be
shunted past the Pulmonary Artery and into
Aorta. With increase in pO2 at birth, the Ductus
Arteriosis closes and blood is forced to go to
the lungs for oxygenation.
• Foramen Ovale – Valve (flap-type) that closes
when pressure in left side of heart increases
upon closure of the Ductus Arteriosis.
ADULT
RIGHT HEART ► LUNGS ► LEFT HEART
↑
↑
LIVER
↓ AORTA
←
←
←
BODY
FETUS
Liver
Ductus
Venosus
Lung
RIGHT HEART ► FORAMEN OVALE ► LEFT HEART
↑
↑
AORTA
PLACENTA
DUCTUS ARTERIOSIS
BODY OF FETUS
Gut
•
•
•
•
Filled with Amniotic Fluid drunk at 500 ml/day
Contains meconium – fecal material
Absorbs amino acids, sugars and electrolytes
Digestion of proteins, aborption of amino acids and
incorporation into fetal tissues
• Colostrum – fluid phase pinocytosis and gut closure
regarding absorption of immunoglobulins
– Passive Immunity – required for piglets and beneficial for
offspring of all species
– Gut maturation
• IGF-I and EGF in colostrum stimulate gut maturation
Renal System
• Normal fetus – 450 ml urine/day into
amniotic sac with turnover of 300 to 600
ml/h of amnionic fluid
• Proteinuria in fetal life to closure of kidney
tubules in neonate
• Absence or malfunction of kidneys leads
to death or retarded development
Respiratory System
• Fetal breathing occurs in utero
• Allows development of intercostal muscles of
chest and diaphragm associated with breathing
Fetal Adrenal Glands
• Norepinephrine
– Release of surfactant from epithelial cells of lung lobuloalveolar structures
– Absorption of liquid from lungs
• Glucocorticoids (Cortisol and Corticosterone)
–
–
–
–
–
–
–
–
Lung maturation
Lactogenesis
Thyroxin to Triiodothyronine
Glucose storage as glycogen
Insulin secretion in response to glucose
Transition from fetal hemoglobin to adult hemoglobin
Closure of Ductus Arteriosis
Parturition
Lung Maturation
• Synthesis and secretion of surfactant by lung
alveolar epithelium
– Glucocorticoids – Synthesis (Transcription and
Translation) of surfactant and storage in cells
– Norepinephrine – Secretion of surfactant
• Surfactant essential for lung alveoli to
maintain integrity and not collapse by
providing high surface tension when stretched.
• Fetuses deficient in surfactant develop Hyalin
Membrane Disease and often die
• Now Pediatricians have artificial surfactant to
decrease risk of Hyalin Membrane Disease
Respiration
• Umbilical Circulation
– pO2
• Artery – 15
• Vein - 25
– pCO2
• Artery – 55
• Vein – 40
• Maternal Uterine Circulation
– pO2
• Artery – 95
• Vein – 35
– pCO2
• Artery – 35
• Vein - 45
ADULT
RIGHT HEART ► LUNGS ► LEFT HEART
↑
↑
LIVER
↓ AORTA
←
←
←
BODY
FETUS
Liver
Ductus
Venosus
Lung
RIGHT HEART ► FORAMEN OVALE ► LEFT HEART
↑
↑
AORTA
PLACENTA
DUCTUS ARTERIOSIS
BODY OF FETUS
Postpartum Uterus
Uterine Involution and Repair
).
11β
hydroxylase
11β hydroxylase for corticosterone
and cortisol
Ovine
Human
Fetal Hypothalamic Pituitary
Adrenal Axis
↓
Placental ←
Estrogens
Fetal Glucocorticoid Production
Corticosterone and Cortisol
↓
Intrauterine
Production of Prostaglandins
→ Placental CRH
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
CRH is Produced by Human Chorion in response to
cortisol from fetal adrenal
CRH stimulates Dehydroepianrosterone Sulfate
(DHAS) from fetal adrenal that is converted to
estrogens by chorion
Glucocorticoids and estrogens stimulate increased
expression of prostaglandins E and F and decreases
PGDF-15 that inactivates PGs
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
Central Characteristics of Human Parturition
Increase in CRH and PGHS-2 in chorion
Decrease in PGDH-15
Increase in FP and EP prostaglandin
receptors
Decreased sensitivity of uterus to
progesterone
Increase in production of estrogens from
DHAS by chorion
Increase in myometrial contractions
Challis et al. J Obstetrics and Gynecology 31:492-499. Fetal
Signals and Parturition
Conversion of Progesterone to Estradiol and Loss of
Progesterone Influence
Increased Contraction Associated Proteins
Oxytocin Receptor
PGF Receptor
Connexion-43 Gap Junction Protein
Recent Suggestion that Increase in Progesterone
Receptor C Isoform Results in Loss of Progesterone
Responsiveness via PR Isoforms A and B in Human
Myometrium (Condon et al. 2006 Mol Endocrinol
20:764-775
Controlling Time of Parturition
• Efficient use of labor and facilities to
reduce neonatal death losses
• Reduce length of gestation
• Increase opportunities for cross-fostering
neonates in event of failure of dam to
accept offspring, cannabilism or failure to
lactate
• Convenience of producer
• In swine, uniformity of post-weaning estrus
Controlling Time of Parturition (continued)
• Swine: Corticoids Ineffective
– PGF-2 alpha – 200 ug cloprostenol or 10 mg Lutalyse at 7
AM and 7 PM with farrowing 24-26 h later.
– Should not be used prior to Day 112 of pregnancy due to
decreased survival of neonate
• Cows; Corticoids, Estradiol and PGF are effective
– 20 mg dexamethasone to dam most commonly used. For
maximal survival of calf, cows should be within 1 week of
term. Some countries with wet and dry season induce
parturition to coincide with rainy season, high nutrient
availability and focus on milk production with calves having
little economic value
• Retained placentae major issue
Controlling Time of Parturition (continued)
• Mare: Corticoids, PGF and Oxytocin
– 2.5 mg PGF (Lutalyse) every 12 hours causes
birth/abortion in late gestation.
– 200 dexamethasone/day for 4 days with foals being
born 72 to 96 h after end of treatment
– 20 IU to 200 IU Oxytocin administered with estradiol
will cause cervical dilation and birth in some cases.
Post-Partum Period
• Cow
– Days 0-12 – Sloughing and Discharge of
endometrial tissue and placenta
– Days 25-30 – Uterine Involution completed
– Days 40-45 – Uterus considered ready for
next pregnancy
– Dairy – First estrus around Day 15 to 20 and
breeding from Day 60
– Beef – First estrus between 60 and 100 days
and breed during desired dates (spring or fall)
Post-Partum Period
• Sheep
– Uterus involuted by Days 25 to 30
• Breed in fall
• Pig
– Uterine involution completed by Days 21 to 28
– Breed at post-weaning estrus (3-7 days)
• Mare
Foal Heat – 5-15 days postpartum
Breed if no complications
Human
Highly variable and related to many factors
Suckling intensity, body condition, nutrition etc