Puerperium and Lactation

Question 1

Puerperium

Answer 1

That period after parturition characterized by the reproductive tract returning to the non-pregnant state to enable the female to become pregnant again (normal cycling of ovaries and uterus)

Question 2

Uterine Involution

Answer 2

The actual physical process of the uterus returning to the normal non-pregnant size and function

Question 3

Lactation

Answer 3

The process of synthesis, secretion, and removal of milk from the mammary gland

Question 4

When do puerperium and lactation occur?

Answer 4

Both start immediately after parturition

Question 5

4 major events

Answer 5

1. Myometrial contractions and ejection of lochia
2. Endometrial repair
3. Resumption of ovarian function
4. Elimination of bacterial contamination in the reproductive tract

Question 6

Why is a short puerperium desirable?

Answer 6

Shortest puerperium in polyestrous species is desired to increase the eligibility for a subsequent pregnancy

eg. Dairy cows: frequent pregnancies max lifetime milk yield

eg. swine or beef cows: shorter interval between pregnancies max meat production (ie. more total offspring)

Question 7

Myometrial contractions

Answer 7

Strong repeated contractions occurring right after parturition (strong for 2-3 days)
>helps discharge fluid
>aids tissue debris removal
>compresses vasculature in uterine wall to minimize hemorrhage
>reduces overall size of uterus

Question 8

What drives myometrial contractions?

Answer 8

Post partum suckling and ocytocin secretion

Question 9

Uterus atrophy

Answer 9

-rapid atrophy (muscle cells decrease by 70%) of uterus to reduce it back to non-pregnant size

**differences between pregnancies (primiparous vs. multiparous) and timing of contractions

Question 10

Lochia

Answer 10

Fluid containing blood, necrotic tissue (fetal placenta, endometrial fragments), and mucous is expelled from vulva after myometrial contractions

-begins 1-2days post partum
-highest volumes in first 10 days in dairy cows, then decreases substantially

Question 11

Lochia in equine

Answer 11

relatively low amount
usually stops 24-48h after foaling

Question 12

Lochia in pig

Answer 12

Discharge is observed for up to 48h post-farrowing

Question 13

Lochia in dog

Answer 13

Discharge immediately after parturition can be green, but changes to bloody mucoid discharge within 12 h

Question 14

Lochia in cat

Answer 14

Obvious vulvar discharge for up to a week after kittening, but completes by 2 weeks

Question 15

Lochia discharge past normal periods

Answer 15

May indicate infection. metritis, endometritis, and may need to be treated

Question 16

Endometrial repair in ruminants

Answer 16

1. Once fetal cotyledons separate from maternal caruncles, vasoconstriction occurs followed by necrosis 48hrs post-partum
2. 5 days, necrosis proceeds quickly, contributing to the lochia content. Leukocytes in necrotic layer, and sloughing complete days 15-19
3. Re-epithelialization occurs by 25-30 days for complete healing

Question 17

Endometrial repair in equine

Answer 17

-Much less repair required due to different placentation (epitheliochorial)

-1 day post-partum, some degeneration of endometrial glands
-by day 5, some inflammatory cells in tissue
-regeneration complete in ~10days

Question 18

Endometrial repair in pigs

Answer 18

-Very small amount of degeneration compared to ruminants, likely due to placentation type

1.Epithelial cells transition from columnar to flat degenerated cells by day 7 post partum
2.Active cell division until endometrial regeneration by day 21 post partum

Question 19

Endometrial repair in dogs

Answer 19

Areas of previous placental attachment (zonary) require ~12 weeks to regenerate

Question 20

Endometrial repair in cats

Answer 20

More rapid repair than in the dog although also zonary

Complete regeneration by ~25-30 days

Question 21

Ovarian Rebound (return to cycle)

Answer 21

After birth, the inhibitory steroids (progesterone) on GnRH are lost and FSH levels build up!

First post partum ovulation is associated with absence in estrus behaviour and interovulatory period can vary

Question 22

Ovarian rebound in ruminants

Answer 22

-Increases in number by days post-partum. Earlier initiation of ovarian cycle before breeding leads to better fertility

**follicular wave emergence= growing follicles, dominant then preovulatory follicle=high estrogen=estrous behaviours
Then ovulation and CL formation=progesterone increases and primes uterus for future

Question 23

Ovarian rebound in equine

Answer 23

Rebound is rapid (5-12 days) with follicular acitivty as early as 2 days PP

Question 24

Ovarian rebound in small ruminants

Answer 24

Seasonal cycles, so cycle at next breeding season after anestrus period

Question 25

Ovarian rebound in pigs

Answer 25

Suckling and weaning have profound effect on rebound

Usually later time of weaning, the shorter the time interval to first estrous

Question 26

Ovarian rebound in cats

Answer 26

Lactation can suppress estrous, but if no kittens, can return to estrous 7-10 days PP

Question 27

Ovarian rebound in dogs

Answer 27

Return to estrous is unpredictable

Parturition is always followed by anestrous

Question 28

Bacteria within the uterus

Answer 28

Uterus is not sterile; contains low levels of commensal and non-pathogenic organisms
-this normal microbiota can be shifted through post partum and may lead to disease

**elevated estradiol can induce immune responses to maintain balance

Question 29

Restoration of uterine environment

Answer 29

Bacterial contamination of the uterus occurs due to relaxation of physical barriers (cervix open)
>repeated contractions/relaxations enhance bacterial contamination via a vacuum effect
>lochia presence can promote bacterial growth

Question 30

Uterine defence mechanisms

Answer 30

Help to clear out the bacterial invaders AND is important for endometrial regeneration

Ex. clearance by 5-7weeks post partum in cows

Question 31

Lactation development

Answer 31

Final mammary development occurs in dam during pregnancy
>alveoli grow into bunches or lobules
>a group of lobules connects into a duct and as a whole is now a lobe
>by end of pregnancy, the lobulo-alveolar structures are 90% of gland

Question 32

What stimulates milk synthesis?

Answer 32

prolactin, placental lactogen, adrenal cortical hormones

Question 33

Milk secretion

Answer 33

Synthesized and secreted by alveolar cells into alveolar lumen
>prolactin=maintains milk production
>suckling stimulates release from anterior pituitary

Question 34

Milk ejection

Answer 34

Active movement of milk from alveoli and alveolar ducts into larger ducts, cisterns, and then teats
>removed by suckling newborn

Question 35

Steps of milk ejection

Answer 35

**Neuroendocrine reflex

1. Sensory activation- auditory, tactile, visual
   2.Neural activation of hypothalamus (inhibitis dopanergic neurons in hypothalamus; dopamine normally inhibits oxytocin)
2. Oxytocin release into blood
3. Contraction of myoepithelial cells
4. Mechanical transfer of milk from alveoli into ducts and eventually to teat/nipple

Question 36

Mammary involution

Answer 36

The process where the mammary alveolar cells stop producing milk and reorganize back to non-pregnant state

1.as milk needs decrease, pressure atrophy or build up of pressure in the gland inhibits alveoli function

2. Cells atrophy. Lymphocytes, macrophages invade tissue and help remodelling