2. When to breed: oestrus and its detection Flashcards
how does progesterone suppress oestrus
- prepares uterus for pregnancy
- inhibits oestrus behaviour
- blocks LH surge
- forms corpus luteum
what initiates the follicular phase
if not pregnant:
- uterine PGF2a
- luteolysis
- progesterone decreases
- increased oestradiol from ovulatory follicle and induce oestrus
describe the oestrus cycle in the normal cow
21 day oestrus cycle
- 17 day luteal phase then
- falling progesterone = 3 days proestrus
- standing oestrus lasts about 1 day
LH surge occurs mid-oestrus
- ovulation occurs 24 hours after LH surge
- therefore ovulation 12h after end of oestrus
when is the opportune time to mate the normal cow
- oestrus lasts up to 1 day and ovulation occurs 12 hours after end of oestrus, thus mating occurs about 1 days prior to ovulation
- oocytes age if not fetilised and usually cannot be fertilised >24h after ovulation (ideall sperm should be present before ovulation)
- for AI: uterine insemination normally undertaken 6-12 hours prior to ovulation (same day as oestrus first observed)
how long is the duration of oestrus in the cow
5-18 hours
how long is the oestrus cycle in the cow
21-22 days
when do cows ovulate
12 hours after end of oestrus
how long is the oestrus cycle of an ewe
17 days
how long is the duration of oestrus in the ewe
24-36 hours
when do sheep ovulate
30-36 hours from beginning of oestrus (towards end of oestrus)
how long is the oestrus cycle of the sow
21 days
how long is the duration of oestrus in the sow
48-72 hours
when does the sow ovulate
35-45 hours from the beginning of oestrus
how long is the oestrus cycle of the mare
21-23 days [19-25d]
how long is the duration of oestrus in the mare
4-8 days
when do mares ovulate
1-2 days before the end of oestrus
how long is the oestrus cycle of the bitch
210 days (varies) -7months
how long is the duration of oestrus in the bitch
7-14 days
when does the bitch ovulate
variable - often 2 days after onset of standing oestrus
what is important to the timin of insemination in the cow and what are some challenges
relatively easy since oestrus is short and tightly regulated to time of ovulation
- inseminate/mate at oestrus
problem: detecting oestrus
what is important about the timing of insemination in the ewe and are there any challenges
not a problem since mated throughout oestrus by a ram
challenge: need correct ram:ewe ratio/identification of mated ewes
Ai: insemination is slightly delayed –> 12h after onset of oestrus
what is important about insemination in the sow and are there any challenges
sows/boars housed separately and sow presented to the boar for mating
- mating and AI usually start on day after the onset of standing oestrus
- 2 inseminations typically used to maximise timing when ovulation occurs
- challenge: oestrus detection is very important
what is important about insemination of the mare and what are some challenges
- return to oestrus is variable
- oestrus length is variable
- therefore mares are problem
- normal practice is to teas daily and breed throughout this period or to monitor ovaries with ultrasound
what is important about insemination of the bitch and what are some challenges
- monoestrus
- oestrus variable/very poorly indicate of time of ovulation
- thus oestrus detection is a poor tool for planning mating
- vaginal cytology and/or plasma progesterone measurement are better indicators
list some oestrus behaviours in cows
- stands to be mounted!!!
- mounts other cows
- reduced milk yield
- brawling/restless
- chin pressing
- swelling of vulva, mucous discharge (bulling slime)
70% of oestrus activity occurs at night
how do you detect oestrus in the cow and why is it important
- examine cows >4 times per day for 30 mins for oestrus behaviour
- classic detection aids (kamars, pedometers, estrotect)
- remote/electronic aids
- low plasma/milk progesterone indicates oestrus is imminent if previously high
- detection of a large dominant follicle (in absence of CL)
imporatnce:
- variable time for return to cyclicity post-partum
- non-detection –> delayed breeding
- job of herdsperson as often not run with bull
- detection rates <50%
list factors that might inhibit oestrus behaviour
- hard slippery floor
- high environmental temp
- high milk yield
- overcrowding
- recent mixing/stress
- lameness
- feeding (big foodies)
list signs of oestrus in the ewe
- restless
- seeks ram
- forms a following harem
- stands for ram
- waggles tail
- moves tail lateally to allow mating
- swollen vulva
- slight mucoid discharge
list signs of oestrus in the sow
- stands firmly to be mounted
- vulval reddening, swelling and congestion prior to oestrus
- seeks the boar, pacing, searching, grunting
- stands for boar
- responds to pheremones
list signs of oestrus in the mare
- oedema in the vulva/mucoid discharge
- elevated tail and lean her hindquarters towards the stallion
- spread hindlegs
- winking
- flehmen response in stallion
- commonly daily teasing is performed
- detection of large follicle on US and absence of CL
- thickened wall of follicle as approaches ovulation
list signs of oestrus and pro-oestrus in the bitch
pro-oestrus
- very long (9 days)
- bitch is attractive but not allow mating
- vulval swelling
- presence of a serosanquinous discharge
oestrus:
- stands to be mated
- deviation of tail
- discharge becomes paler in colour
- reduction in vulval oedema
- assessment of vaginal epithelial cells (clinical)
- plasma progesterone concentrations (clinical)
discuss oestrus in the queen
- pro-oestrus: short and often unnoticed
- induced ovulator
- LH response to mating decreases with each day of oestrus and follicles ultimately regress (oestrus detection important)
signs of oestrus:
- increased vocalisation, rubbing and rolling
- increased activity and will seek tom
- possible slight mucoid vulval
- extending hindlegs and demonstrating lordosis
- erect tail held to one side
what is silent oestrus and why does it occur
ovulation without signs of oestrus
- typically at first oestrus after seasonal anoestrus or partuition
- no pregesterone priming on brain centres
- no progesterone fall to trigger oestrogen receptor expression in brain
- no sudden release of oestradiol
how long is oestrus in the cow
18 hours
when is AI typically first conducted on sow
day after oestrus first observed
what clinical tool can we use to optimise the time of mating in the dog
blood progesterone
