Chapter 9 Parturition and Postpartum Recovery

Chapter 9 Parturition and Postpartum Recovery

9-1 Overview of the parturition process

A. Definition: Birth process

From a) softening and initial dilation of cervix
b) uterine contraction
To expelling fetus and its associated placental membranes

B. Process of parturition: Time required for 3 stages: See TABLE 9-1

a. 1st stage 刳洘悢: Complete dilation of cervix and entry of fetus into cervix
b. 2nd stage 奡蘦悢: Expulsion of fetus
c. 3rd stage 涖艂悢: Expulsion of placenta

9-2 Approaching parturition

9-2-1 Rotation to birth position

* Presentation, position and posture of fetus for parturition:
a. Presentation 鷖糔: Longitudinal 蹥糔: Anterior 婩糔; Posterior 畯糔 Transverse 𤇍糔: Dorsal 褁糔; Ventral 嗕糔
b. Position 鷖𨫞: In longitudinal: Position of fetal back (dorso-)

(See Ref.Fig. Figure 6-3 of Salisbury et al., 1978)
To Sacrum 葞鷖𨫞
Pubis 欞鷖𨫞
Left ilium 韺鰤鷖𨫞
Right ilium 橔鰤鷖𨫞
In transverse: Position of fetal head (cephalo-)

c. Posture 鷖嵺: Positions of fetal head, neck and legs to its own body

A. Normal birth position:

For monotocous species (Ewe, Doe, Cow and Mare):
Longitudinal, anterior presentation with dorso-sacral position and posture as FIGURE 9-1.

Figure 9-1 Normal birth position in cows which is assumed near the end of the gestation period

Fetus: On its back with its feet pointing up during gestation ⊥ As parturition approaches: Rotates into the birth position.

B. Abnormal presentations of calf for parturition: See FIGURE 9-2

Figure 9-2 (a-h) Abnormal birth positions that may be seen in cows.

Assistance in delivery: Reposition the fetus, not to break umbilical cord:
If broken:be quickly removed. Relaxin inj.: facilitate repositioning.

9-2-2 Mammary gland changes

A. Development of mammary gland:

a. Development of mammary ducts and secretory tissue during late gestation: By singergistic action of E2 and P4
b. Enlagement of mammary gland during prepartum period: By filling with milk

B. Milk synthesis: By synergism of PRL and other hormones

C. Milk let-down: By oxytocin during labor; frequent milk-leaking from teats

9-2-3 Other changes

A. Expansion of pelvis and birth canal: By relaxin synergizing with E2 ⊥ A sinking around tailhead.

B. Vulva: soften and swollen

C. Cervical mucus: Secreted by E2 ⊥ loosen cervical mucous plug

D. Nesting instinct: especially in sow: By PRL

9-3 Parturition

9-3-1 Hormonal initiation

* Rapid changes in hormone levels: See FIGURE 9-3 for ewes

Figure 9-3 Relative changes in hormone concentration near the time of parturition

A. Cow,Sow.Doe and Ewe:

a. As fetal brain matured :

Fetal hypothalamus ⊥ CRF
⊿
Fetal hypohpysis ⊥ ACTH
⊿
Fetal adrenal cortex ⊥ Glucocorticoids as cortisol
⊿ ⊿
E2 ∠ Placenta ⊥ Convert P4 into E2
(cow,sow,doe) (ewe) ⊿ ⊿
PGF2丟 ∠ Uterus PGF2@ ∠ Uterus ⊿
P4 dec. ∠ Luteolysis

b. Relaxin:

In sow: Prepartum great inc. then rapid dec. ⊥ helpful for delivery

c. Oxytocin:

1) Movement of fetus into cervical canal and
2) Fetal motility due to anoxia of fetus from dec. blood flow by uterine contraction ⊥ Stimulate sensory nerves in cervix and vagina ⊥ Oxytocin release ⊥ Inc. PGF2丟

B. Mare

Less known. Similar to ewes. But the role of inc. P4 in late gestation: ?

9-3-2 Regulation of the physiological events

* Two main physiological events in parturion:

a. Dilation of cervix:
Relaxin with E2: Soften cervix and cause secretion of cervical mucus Allanto-chorion, amnion and fetus forced into cervix: further dilation
b. Utrine contraction
1) Reduced P4: Remove inhibition of uterine contraction
2) Inc. E2: Up-regulate uterine receptors of E2 and oxytocin ⊥ Inc. responsiveness of myometrium to oxytocin
3) Initial uterine contraction: caused by endometrial PGF2@ by inc. E2 : Weak and irregular at about 15min. intervals ⊥ Stronger, more rhythmic and more frequent.
4) As fetus pushed into cervix: Oxytocin + PGF2@ ⊥ Peak contraction; occurring at 2 min.intervals and lasting for approx. 1 min.
5) Following expulsion of fetus: Uterine contractions: diminished but continue for another 1 to 2 days.
6) Secondary oxytocin surge: associated with expulsion of placenta.

9-4 Care of the newborn

Fetus: Under germ-free environment, temperature regulation, nutrient and oxygen requirements by maternal system.
Newborn: Must survive independently.

A. Circulatory and respiratory systems

a. Changed from placental circulation and respiration to fetal lung respiration and fetal heart circulation.
b. Initiation of lung respiration: Due to stimulation of respiratory center in brain by inc. CO2 level.

B. Thermoregulatory mechanisms

Not well developed: Reduced survival in extremely hot or cold environment.

C. Absorption and metaboilsm of nutrients

Not well developed: Glycogen stored in liver and muscles: used during this adjustment period.

D. Immune status

a. Immune system of neonate: not challanged.
b. Maternal antibodies: Not pass through placental barrier*
Absorbed through intestines until 24# hrs after birth
Antibody conc. in colostrum decline as time passes.
c. Colostrum should be fed as early as possible: 6% of birth wt within 6 hrs.
Storage for later use: By fermentation or freezing
* In human: Maternal antibodies pass through placenta, but not absorbed through intestines of neonate # LeBlnac,1986, In Current Theraphy in Theriogenology (2nd ed.) pp.224-226

E. Other cares of newborn

a. Painting umbilical stump with iodine to lessen infection
b. Clean and dry the newborn, especially in cold weather
c. Breathing trouble: Stimulate by slapping or artificial respiration

9-5 Retained placentae

A. Definition: Entire or parts of placenta: not expelled in 12 hrs after delivery of fetus Occurs mainly in cows among farm animals

B. Incidence: 5-15% in healthy herds of cows. High in the following status:

a. Short gestation (270-275 days)
b. Twin births: 43% by Morris and Erb,1957
c. High milk producers
d. Dairy breeds
e. Dystocia
f. Selenium deficiency: Over 50% in Se deficient areas
g. Vit A deficiency
h. Abortion
i. Induced calving

C. Subsequent reproductive problems from retained placenta

a. Retention for another 5 to 6 days⊥ Decaying tissues⊥ Uterine infection∟
b. Low fertility from uterine infection
c. Stress from placenta retention⊥ Reduce milk production

D. Prevention

a. No satisfactory measures
b. PGF₂丟 inj. just after delivery of fetus: Effective in cases of a.b.e.and i of " B. Incidence"
c. Administration of Se and Vit E: For the case of f.
d. Feeding green forage: For the case of g.

E. Treatment

a. To do nothing: Uterine infections and toxemia
b. Manual removal 48 to 72 hrs after parturition, followed by intrauterine treatments with antibiotics⊥ Frequently causes tears in uterus ⊥: Reduce reproductive efficiency
c. Placing antibiotic boluses into uterus daily or infusion of 4 liters of antibiotic solution into uterus 24 to 36 hrs after parturition. Draw the membranes back 5 to 6 days. Only if the animal's temperature is elevated: Systemic inj. with antibiotics

9-6 Postpartum recovery

* Definition: To return normal estrus and uterine environment to a state that will support another pregnancy

Farrowing estrus: At a few days postpartum: Almost failure to ovulate
Foaling estrus: At 8 to 15 days postpartum: Breed only at complete recovery

9-6-1 Postpartum ovulation and estrus

A. Quiet ovulations: Ovulation without evidence of estrus at 20 to 30 days postpartum, especially in dairy cows .

B. Postpartum anestrus: Anestrus from suckling

a. Beef cows

1) Anestrus period: Gerrits et al.(1979) In Animal Reproduction (ed.by Hawk) pp.413: Average range: 55-65 days.
Inskeep and Lishman (1979) In Animal Reproduction(ed. by Hawk) pp.277:
Presence of CL or estrus observed from 30 to 99 days in 1,164 cows: 57%.

2) Effect of suckling on postpartum anestrus: Estrus delays 2 to 3 times
longer in suckling cows; Short et al.(1976) J.Animal Sci.43:304: 65 d
in suckled, 25 d in nonsuckled and 12 d in mastectomized beef cows.

b. Dairy cows: 4x milking delays return to estrus
c. Sows: Return to estrus: 1) at 1 wk after weaning if weaned at 5 to 8 weeks postpartum or 2) at 3 wks postpartum if weaned at 1 week

d. Mechanisms and/or causes of postpartum anestrus
1) Suckling ⊥ PRL inc.+ ⊥ inhibit pulsative inc. in GnRH ⊥ inhibit episodic surges in FSH and LH ⊥ inhibit growth and maturation of follicles⊥inhibit return to estrus. Removed or limited suckling stimulus ⊥ More frequent pulses of GnRH, FSH and LH ⊥ accelerate return to estrus.
2) Low nutrittion during gestation or postpartum: delay return to estrus inc. quiet ovulations in cows: See TABLE 9-2.

3) Infectious diseases, metabolic disorders, uterine infections and other health problems

9-6-2 Involution of the uterus

A. Definition

1)Return of postpartum uterus to normal nonpregnant state :

a) Size,
b) Recovery of uterine tone,
c) Recovery and repair of endometrium

B. Period of involution

a. Mare: Size: involuted within 2 wks
b. Sow: Nearly involuted in 2 wks, but weaning at 3 wks and breeding at 4 wks resulted in smaller litter size ∠ embryo loss ∠ disturbances in implantation process ∠ incomplete involution
c. Ewe: Size: involuted within 2 wks, but complete recovery of endometrium: in 4 wks
d. Cow: 1) FIGURE 9-4: Nearly involuted: in 45 days in uncomplicated parturition, and histologically normal endometrium: in 60 days

2) An experiment:

(1) Size: in 30 days,
(2) Tone of nonpregnant horn: in 30 days,
(3) Tone of pregnant horn: in 45 days

3) Size of pregnant horn: larger than nonpregnant horn after complete involution

4) Delayed involution: From placental retention and/or uterine infection