Fertility and Breeding time in the female Flashcards
What is oestrus
When the female becomes sexually receptive to the male
Can be proceed by period of pro-oestrus and/or other clinical signs
Classic sign is “stands to be mate by the male”
Varying intensity, length and timing of ovulation relative to oestrus across species
When does oestrus occur
In the latter part of the follicular phase (after luteal phase in polyoestrus species)
Oestrus is driven by increasing oestradiol concentrations (often this requires a prior fall in progesterone)
Once puberty has been initiated
Return to oestrus after parturition/lactational anoestrus
Resumption of cyclicity after seasonal anoestrus
Considerations for the optimal time to mate related to the male
Introduction of a specific (high value) male
- Often, management requires this at specific time
- Controlled mating
Artificial insemination
- Need to monitor for oestrus signs
- Might synchronise ovulation instead
Considerations for the optimal time to mate for female
Period of pre-ovulatory follicle growth maturation
Increasing oestradiol that induces oestrus and the LH surge
But, oestrus does not necessarily predict exact time of ovulation
Oocytes in most species are short-lived
What is the fertilisation period
The fertilisation period is the time when oocytes are available to be fertilised by sperm – in most species this is immediately after ovulation for up to …… hours (but days in the bitch!)
What is the fertile period
Where mating could result in pregnancy
What happens to progesterone through the oestrus cycle
Decreases during luteolysis
Thus precedes the follicular phase
Indicates that oestrus will occur soon
Need to be low for oestrus
In dogs, increase in progesterone indicate luteinisation and thus ovulation is imminent
What happens to oestradiol through the oestrus cycle
Elevated during follicular phase
Often, similar to oestrus profile
Only really measure in research settings
What happens to GnRH through the oestrus cycle
GnRH surge triggered prior to ovulation
Relatively shorted-lived
No commercial kits available
What happens to LH through the oestrus cycle
how many days post surge is optimal to mate dogs
LH surge triggers ovulation
Generally, time to LH surge and ovulation tightly regulated
Used in humans to predict optimal chances for pregnancy
Commercial kits available for cats and dogs
Frequent sampling required. Day 4-7 post surge optimal (dogs)
What does the absence of a CL in the ovary on ultrasound indicate
An active CL, means progesterone is high and thus ovulation cannot occur
Note: CL might be regressing. If so: likely to be smaller, reducing in size and increased echogenicity
Size for cow follicle
needs to be at least 10 mm, typically 16-20mm; >20mm likely to be pathology
Normal sizes for mare ovary
Typically 30-50mm; as approaches ovulation, follicle stops growing – optimal time to introduce stallion.
What does follicular morphology on ultrasound indicate
how does it change near ovulation
Used as a key indicator that ovulation is imminent
As follicle approaches ovulation follicular shape can change
Loses its turgidity and becomes more irregular in shape
In mares, the follicular wall will thicken (luteinise)
In the mare, what would you find on rectal palpation in the oestrogen dominated part of the cycle
Cervix broad* (bigger diameter) & soft
Uterus larger and oedematous (soft
In the mare, what would you find on rectal palpation in the progesterone dominated part of the cycle
Cervix hard & narrow* (small diameter)
Uterus smaller with increased tone
In the cow, what would you find on rectal palpation in the oestrogen dominated part of the cycle
Cervix narrow* and tense
Uterus oedematous with increased tone
In the cow, what would you find on rectal palpation in the progesterone dominated part of the cycle
Cervix flaccid and soft
Uterus flaccid with reduction in tone
(Cows ovulate at the END of oestrus so want to be mated in the luteal phase)
What is the effect of giving GnRH
induces LH surge within hours and ovulation 1 day or so later
What is the effect of giving HCG
LH activity
will directly induce ovulation
What is the benefit of pharmacologically controlling ovulation
can time mating/ AI accordingly
What does the OvSynch protocol for cattle consist of
Day 0= GnRH
Day 7= PGF2a
Day 9= GnRH
Day 10= AI
