Oestrus and its detection

Question 1

What is the function of progesterone

Answer 1

Prepares uterus for pregnancy
Inhibits oestrus behaviour
Blocks LH surge (not tonic LH secretion)

Question 2

What is the function of FSH?

Answer 2

Stimulates development of antral follicles including selection of dominant follicle

Question 3

What happens in the luteal phase if the animal does not become pregnant?

Answer 3

Uterine PGF2a acts on CL
Luteolysis
Decreased progesterone
Increased oestradiol from ovulatory follicle => oestrus

Question 4

Describe the oestrus cycle of a cow

Answer 4

21 days:
- 17 day luteal phase
- 3 days proestrus - falling progesterone
- Standing oestrus ~ 1 day

Question 5

When does ovulation occur in relation to oestrus in cows?

Answer 5

LH surge occurs mid-oestrus
Ovulation occurs 24 hours after LH surge
Ovulation occurs 12hrs after end of oestrus

Question 6

When is mating and AI done in cows?

Answer 6

Mating occurs ~1 day prior to oestrus
Uterine insemination undertaken same day as oestrus first observed

Question 7

Why is timing of insemination/mating in a cow easy?

Answer 7

Oestrus is short and tightly regulated to time of ovulation

Question 8

Why is timing of insemination/mating easier in a ewe than a cow?

Answer 8

Longer oestrus so mated throughout oestrus by a ram (ram detectds oestrus)
AI is slightly delayed compared to cow - 12hrs after onset of oestrus

Question 9

Describe the timing of ovulation in a sow

Answer 9

35-45 hrs after beginning of oestrus (before it ends)
Oestrus detection is important

Question 10

Describe the timing of AI/mating in a sow

Answer 10

usually start day after onset of standing oestrus
2 inseminations typically used

Question 11

Why is timing of AI/mating in mares difficult?

Answer 11

Return of oestrus and oestrus length is variable

Question 12

Why is timing of AI/mating difficult in bitches?

Answer 12

mono-oestrus - time between oestrus cycles could be 6-8 months
Oestrus variable and poorly indicate timing of ovulation
Oestrus detection is poor tool to plan mating

Question 13

how long is oestrus and when does ovulation occur in a dog?

Answer 13

7-14 days
ovulation occurs ~2 days after onset of standing oestrus

Question 14

Describe the progressive oestrus behaviour in cows

Answer 14

Swelling of vulva, mucous discharge (occurs throughout, even when oestrus ending)
Reduced milk yield
Brawling, restless
Chin pressing
Mounts other cows
Stands to be mounted (most important sign)
Bloody discharge when oestrus endind

Question 15

How do you detect oestrus in a cow in a clinical assessment

Answer 15

Low plasma/milk progesterone
Clinical detection of a large, dominant follicle (absence of CL) - should ovulate shortly

Question 16

What factors may inhibit oestrus behaviour in a cow?

Answer 16

hard, slippery floor
high temp
high milk yield
overcrowding
recent mixing/stress
lameness
feeding

Question 17

What is the benefit of ovulation synhcronisation in cows?

Answer 17

Ovysynch (GnRH and PGF2a)
removes need for oestrus detection
Can reduce time from calving to re-conceiving

Question 18

What are signs of oestrus in the ewe?

Answer 18

Restless - seeks ram
Stands for ram - waggles tail and move tail laterally to allow mating
Swollen vulva with mucoid discharge

Question 19

What are the signs of oestrus in the sow?

Answer 19

stands firmly to be mounted (use back pressure test)
Vulval reddening, swelling and congestion
Seeks boar, pacing, searching, grunting
Responds to pheromones

Question 20

What are the signs of oestrus in the mare

Answer 20

Vulva: oedema/mucoid discharge
Elevated tail and lean her hindquaters towards stallion
Spreads hindlegs
‘winking’ - repeated exposure of clitoris
Induces flehmen response in stallion

Question 21

Describe the signs of pro-oestrus and oestrus in the bitch

Answer 21

PRo-oestrus:
- bitch is attractive but doesn’t allow mating
- vulval swelling
- serosanguinous discharge
Oestrus:
- stands to be mated
- tail deviation
- paler discharge
- reduction in vulval oedema

Question 22

Describe the clinical assessment of oestrus detection in the bitch

Answer 22

Vaginal epithelial cell microscopy:
- assess vulval softening
- examine appearance of vaginal cell wall (more cornified, less RBCs, anuclear)

Plasma progesterone conc:
- detecting rise in progesterone that precedes ovulation

Question 23

what are the signs of oestrus in the queen?

Answer 23

increased vocalisation, rubbing and rolling
increased activity
slight mucoid vulval discharge
tail erect and held to side
extends hindlegs
stand to be mated by lowering front legs

Question 24

When does anoestrus occur physiologically?

Answer 24

During lactation/presence of offspring
Due to seasonality: short or long day breeders
Monoestrus breeders e.g., bitches

Question 25

When does anoestrus occur pathologically

Answer 25

Stress
Ovarian pathologies:
- cystic ovarian disorders (follicles don’t stop growing)
- inactive ovarian activity

Question 26

What is silent oestrus and when does it occur?

Answer 26

Ovulation with limited signs of oestrus
Occurs at 1st oestrus after seasonal anoestrus or parturition:
- no progesterone priming on brain centres
- no progesterone fall to trigger oestrogen receptor expression in brain
- no sudden release of oestradiol

Question 27

What is the clinical relevance of silent oestrus in dairy cows?

Answer 27

Will occur if in severe negative energy balance:
- protective mechanism to prevent early breeding
- energy directed to lactation reduces sexual desire
Missed opportunities to breed
Solutions:
- ovysynch - removes need to detect oestrus
- profiling progesterone levels in milk