Oestrus and its detection Flashcards
What is the function of progesterone
Prepares uterus for pregnancy
Inhibits oestrus behaviour
Blocks LH surge (not tonic LH secretion)
What is the function of FSH?
Stimulates development of antral follicles including selection of dominant follicle
What happens in the luteal phase if the animal does not become pregnant?
Uterine PGF2a acts on CL
Luteolysis
Decreased progesterone
Increased oestradiol from ovulatory follicle => oestrus
Describe the oestrus cycle of a cow
21 days:
- 17 day luteal phase
- 3 days proestrus - falling progesterone
- Standing oestrus ~ 1 day
When does ovulation occur in relation to oestrus in cows?
LH surge occurs mid-oestrus
Ovulation occurs 24 hours after LH surge
Ovulation occurs 12hrs after end of oestrus
When is mating and AI done in cows?
Mating occurs ~1 day prior to oestrus
Uterine insemination undertaken same day as oestrus first observed
Why is timing of insemination/mating in a cow easy?
Oestrus is short and tightly regulated to time of ovulation
Why is timing of insemination/mating easier in a ewe than a cow?
Longer oestrus so mated throughout oestrus by a ram (ram detectds oestrus)
AI is slightly delayed compared to cow - 12hrs after onset of oestrus
Describe the timing of ovulation in a sow
35-45 hrs after beginning of oestrus (before it ends)
Oestrus detection is important
Describe the timing of AI/mating in a sow
usually start day after onset of standing oestrus
2 inseminations typically used
Why is timing of AI/mating in mares difficult?
Return of oestrus and oestrus length is variable
Why is timing of AI/mating difficult in bitches?
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
how long is oestrus and when does ovulation occur in a dog?
7-14 days
ovulation occurs ~2 days after onset of standing oestrus
Describe the progressive oestrus behaviour in cows
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
How do you detect oestrus in a cow in a clinical assessment
Low plasma/milk progesterone
Clinical detection of a large, dominant follicle (absence of CL) - should ovulate shortly
What factors may inhibit oestrus behaviour in a cow?
hard, slippery floor
high temp
high milk yield
overcrowding
recent mixing/stress
lameness
feeding
What is the benefit of ovulation synhcronisation in cows?
Ovysynch (GnRH and PGF2a)
removes need for oestrus detection
Can reduce time from calving to re-conceiving
What are signs of oestrus in the ewe?
Restless - seeks ram
Stands for ram - waggles tail and move tail laterally to allow mating
Swollen vulva with mucoid discharge
What are the signs of oestrus in the sow?
stands firmly to be mounted (use back pressure test)
Vulval reddening, swelling and congestion
Seeks boar, pacing, searching, grunting
Responds to pheromones
What are the signs of oestrus in the mare
Vulva: oedema/mucoid discharge
Elevated tail and lean her hindquaters towards stallion
Spreads hindlegs
‘winking’ - repeated exposure of clitoris
Induces flehmen response in stallion
Describe the signs of pro-oestrus and oestrus in the bitch
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
Describe the clinical assessment of oestrus detection in the bitch
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
what are the signs of oestrus in the queen?
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
When does anoestrus occur physiologically?
During lactation/presence of offspring
Due to seasonality: short or long day breeders
Monoestrus breeders e.g., bitches
When does anoestrus occur pathologically
Stress
Ovarian pathologies:
- cystic ovarian disorders (follicles don’t stop growing)
- inactive ovarian activity
What is silent oestrus and when does it occur?
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
What is the clinical relevance of silent oestrus in dairy cows?
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
