Uterine Involution and Return to Cyclicity

Question 1

What happens during the post-partum period?

Answer 1

Uterine involution, elimination of bacterial contamination from reproductive tract, resumption of ovarian function, lactation/suckling

Question 2

What is uterine involution?

Answer 2

Reduction in uterine size, endometrial repair, expulsion of lochia

Question 3

What are the mechanisms of uterine involution?

Answer 3

Myometrial contractions – peristaltic wave towards cervix, discharge of fluid/tissue debris, compress vasculature, stimulated by oxytocin and PGF2α
Co-ordinated atrophy – reduction in myometrial cell size

Question 4

What is lochia?

Answer 4

Uterine discharge, second cleansing

Question 5

What happens during endometrium repair?

Answer 5

Restoration of caruncle – sloughing of cotyledon, necrosis & tissue remodelling

Question 6

How does uterine involution differ in the mare?

Answer 6

Extremely rapid, little endometrial disruption (normal by day 14), postpartum infection is normal and is eliminated by foal heat

Question 7

What are the two lochia secreted in the bitch?

Answer 7

1st lochia – immediate, green

2nd lochia – 4-6 weeks later, normal

Question 8

What role does oestradiol play in elimination of bacterial contamination?

Answer 8

Oestradiol promotes phagocytosis by leukocytes

Question 9

List 3 conditions/situations that predisposes the uterus to bacterial contamination

Answer 9

Retained fetal membranes, dystocia, dead fetus

Question 10

List 3 effects of uterine excessive bacterial contamination on reproductive function

Answer 10

Increases time of return to cyclicity, reduced fertility, slows uterine involution

Question 11

What is endometritis?

Answer 11

Persistent infection, inflammation of the endometrium, caused by opportunistic pathogens such as Trueperella pyogenes, high incidence, significant cause of infertility, can be treated with antibiotics &/or oxytocin

Question 12

Describe the sequence of events that result in resumption of ovarian activity resuming after parturition in dairy cows

Answer 12

At parturition there is regression of the CL
First few days post-partum, P4 & E2 are low, GnRH is initiated, stimulates the release of FSH, pituitary now responsive (previously was inhibited by high levels of P4)
FSH will assist in follicular development, growing follicle secretes E2 which acts on the hypothalamus and causes a surge in LH
LH surge causes ovulation
follicle will then form a CL  resumption in activity
First cycle is typically short (12 days in a cow) and silent

Question 13

List 5 factors which can influence the timing of ovarian rebound

Answer 13

Metabolic stress, infection, dystocia, poor follicular development, presence of offspring