2. When to breed: oestrus and its detection

Question 1

how does progesterone suppress oestrus

Answer 1

• prepares uterus for pregnancy
• inhibits oestrus behaviour
• blocks LH surge
• forms corpus luteum

Question 2

what initiates the follicular phase

Answer 2

if not pregnant:
- uterine PGF2a
- luteolysis
- progesterone decreases
- increased oestradiol from ovulatory follicle and induce oestrus

Question 3

describe the oestrus cycle in the normal cow

Answer 3

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

Question 4

when is the opportune time to mate the normal cow

Answer 4

• 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)

Question 5

how long is the duration of oestrus in the cow

Answer 5

5-18 hours

Question 6

how long is the oestrus cycle in the cow

Answer 6

21-22 days

Question 7

when do cows ovulate

Answer 7

12 hours after end of oestrus

Question 8

how long is the oestrus cycle of an ewe

Answer 8

17 days

Question 9

how long is the duration of oestrus in the ewe

Answer 9

24-36 hours

Question 10

when do sheep ovulate

Answer 10

30-36 hours from beginning of oestrus (towards end of oestrus)

Question 11

how long is the oestrus cycle of the sow

Answer 11

21 days

Question 12

how long is the duration of oestrus in the sow

Answer 12

48-72 hours

Question 13

when does the sow ovulate

Answer 13

35-45 hours from the beginning of oestrus

Question 14

how long is the oestrus cycle of the mare

Answer 14

21-23 days [19-25d]

Question 15

how long is the duration of oestrus in the mare

Answer 15

4-8 days

Question 16

when do mares ovulate

Answer 16

1-2 days before the end of oestrus

Question 17

how long is the oestrus cycle of the bitch

Answer 17

210 days (varies) -7months

Question 18

how long is the duration of oestrus in the bitch

Answer 18

7-14 days

Question 19

when does the bitch ovulate

Answer 19

variable - often 2 days after onset of standing oestrus

Question 20

what is important to the timin of insemination in the cow and what are some challenges

Answer 20

relatively easy since oestrus is short and tightly regulated to time of ovulation
- inseminate/mate at oestrus

problem: detecting oestrus

Question 21

what is important about the timing of insemination in the ewe and are there any challenges

Answer 21

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

Question 22

what is important about insemination in the sow and are there any challenges

Answer 22

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

Question 23

what is important about insemination of the mare and what are some challenges

Answer 23

• 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

Question 24

what is important about insemination of the bitch and what are some challenges

Answer 24

• 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

Question 25

list some oestrus behaviours in cows

Answer 25

- 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

Question 26

how do you detect oestrus in the cow and why is it important

Answer 26

- 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%

Question 27

list factors that might inhibit oestrus behaviour

Answer 27

- hard slippery floor - high environmental temp - high milk yield - overcrowding - recent mixing/stress - lameness - feeding (big foodies)

Question 28

list signs of oestrus in the ewe

Answer 28

- restless - seeks ram - forms a following harem - stands for ram - waggles tail - moves tail lateally to allow mating - swollen vulva - slight mucoid discharge

Question 29

list signs of oestrus in the sow

Answer 29

- 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

Question 30

list signs of oestrus in the mare

Answer 30

- 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

Question 31

list signs of oestrus and pro-oestrus in the bitch

Answer 31

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)

Question 32

discuss oestrus in the queen

Answer 32

- 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

Question 33

what is silent oestrus and why does it occur

Answer 33

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

Question 34

how long is oestrus in the cow

Answer 34

18 hours

Question 35

when is AI typically first conducted on sow

Answer 35

day after oestrus first observed

Question 36

what clinical tool can we use to optimise the time of mating in the dog

Answer 36

blood progesterone