Reproductive Endocrinology in SAs Flashcards
What are the parts of the oestrus cycle and the hormones that dominate during these periods?
Pro-oestrus - Oestrogen Oestrus - Oestrogen Metoestrus - Transitional Dioestrus - Progesterone Anoestrus (none)
When does the bitch ovulate?
Spontaneously at the end of a variable length follicular phase, 4-28 days but usually around 9.
Outline the timing of a bitches oestrus cycle.
Pro-oestrus - 9 days
Oestrus - 9 days
Pregnancy/Dioestrus - 60 days (as CL only progesterone producing organ in bitch)
Anoestrus - > 90 days
Outline the changes in FSH and LH in the lead up to ovulation in the bitch.
FSH is high in late anoestrus/proestrus whereas LH starts low and then rapidly increases. In early proestrus LH is low and so is FSH but then LH peaks prior to ovulatation then FSH peaks 1 day after ovulation.
What hormone does a dominant follicle lose responsiveness to?
FSH
What is strange about the meiotic events of the bitch?
The 1st meiotic division is completed after ovulation.
What is needed for secretion of progesterone from the CL?
LH -
Progesterone (auto/paracrine) -
PRL
Why is relaxin the only reliable hormonal indicator of distinguishing a pregnant and psuedopregnant bitch?
Relaxin is the only hormone that is placenta specific.
- Progesterone is secreted by the CL which is present for the duration of pregnancy and the same length of time in a non-pregnant bitch.
- PRL levels reach similar levels in pregnant and non-pregnant bitches
How can luteolysis be induced?
PGF2a high dose
FP receptor antagonist
GnRH agonist (continuous)/antagonist
Dopamine (lower PRL after d25)
When are relaxin levels elevated during bitch pregnancy?
21-24days
What options are there for controlling oestrus in the bitch?
Progesterone not possible as:
- Not active orally and
- Short duration when given parentally
Synthetic Progestagens
- First gen may increase GH secretion
- Proligesterone is the best as it is anti-gonadotrophic, is weakly progestagenic and antioestrogenic.
Testosterone
-Active orally but may cause enlarged vulva/clitoris and may affect fertility.
What can be used to control psuedopregnancy?
Synthetic progestagens to supress PRL release
Oestragen and androgen combination to same effect
Dopamine agonist (bromocriptine)
What happens to progesterone levels in the non-pregnant queen that has ovulated?
Luteolysis occurs about day 30 and progesterone falls from this point. Animals that are pseudopregnant have persistent progesterone levels.
What can the interoestrus interval tell us about the conception/ovulation of the quesn?
Failure to ovulate - 21 days
Failure to convcieve but ovulation - 50 days
Pregnant - 65 day luteal phase
Why are the clinical signs of pseudopregnancy in the queen different to that of the bitch?
Mammary development, lactation and behavioural changes do not occur. This is due to PRL not being produced in the non-pregnant animal. The only clinical sign of psuedopregnancy in the queen is a failure to return to oestrus.
