16.8.1: Introduction to repro week and cyclicity in the bitch and queen Flashcards
The bitch is
* Polyoestrus
* Monoestrus
Monoestrus
Oestrus is followed by an anoestrus phase (lasting approx. 7 months)
Which is the main luteotrophic hormone in the bitch?
Prolactin
This hormone supports and maintains the function of CL
What happens if you give a prolactin inhibitor to a pregnant bitch?
- Prolactin inhibitor removes support for CL
- Progesterone falls
- Abortion occurs
What is it important to establish before giving prolactin inhibitor to a bitch with pseudopregnancy?
That the bitch is not pregnant - if she is, prolactin inhibitor will cause abortion.
What is the role of prolactin in the bitch?
- Main luteotrophic hormone
- From Day 21 progesterone concentrations decline
- This decline stimulates a rise in prolactin which supports and maintains the CL
Where is progesterone produced during pregnancy in the bitch and why does this matter?
Progesterone is only produced in the ovary
* Ovariectomy at any stage of pregnancy will result in pregnancy loss
How can we terminate the luteal phase in the bitch?
Repeated administration of a prolactin inhibitor (e.g. cabergoline a.k.a. Galastop) from Day 21 in cycle onwards
Which species are represented with the progesterone graphs here?
- Top - cow - non-seasonal polyoestrus
- Bottom - dog - monoestrus
Both are non-pregnant
A bitch with mammary gland enlargement is likely to be in which phase of the cycle?
Luteal phase
How should you judge if a cell on cytology is big or small?
Assess nuclear to cytoplasmic ratio
Key feature of the luteal phase on vaginal cytology
Return of neutrophils
1
GnRH
2
FSH
3
LH
Surge in which hormone triggers ovulation?
LH
This image shows the oestrus cycle of which species?
Dog
What is the inter-oestrus interval in the bitch?
a) 9 months
b) 7 months
c) 6 months
d) 11 months
b) 7 months
The bitch is…
a) an induced ovulator
b) an spontaneous ovulator
b) an spontaneous ovulator
Polyoestrus
One oestrus cycle follows the other without a period of anoestrus.
e.g. in the cow
The bitch is monoestrus
What does this graph show regarding the progesterone profiles of the pregnant and non-pregnant bitch?
The progesterone profiles of the pregnant and non-pregnant bitch are very similar (slightly higher concentration in the pregnant animal)
Explain the indicated section of the graph and the change in hormone concentration shown here
The spikes in prolactin as associated with lactation
What happens if you give a prolactin inhibitor to the pregnant bitch at the time indicated by the star?
- Prolactin is not yet supporting the CL
- The prolactin inhibitor will not have any effect at this stage
- If given once prolactin concentrations rise (i.e. later on when prolactin is supporting the CL), the prolactin inhibitor will cause abortion
Progesterone is produced by which structures in the bitch and queen?
a) placenta
b) ovary
c) both
d) neither
b) ovary only
This means ovariectomy/loss of support for the CL at any stage during pregnancy will result in pregnancy loss.
Which hormones would you expect to be elevated in the non-pregnant bitch? What effect would these have?
- Elevated progesterone -> mammary enlargment, potential for milk secretion
- Elevated prolactin -> milk production, behavioural changes typical of pregnancy
This graph shows progesterone concentrations in the non-pregnant animal of which species?
Dog
Which species?
Cow
Which species?
Ewe
Which species?
Mare
Which species?
Bitch
Which species?
Queen
How does season of birth impact the age a female kitten will be when they enter puberty?
- Cats are seasonal long-day breeders
- A kitten born in spring will come into puberty next spring (12 months old)
- A kitten born in autumn will come into puberty next spring (6 months old)
The queen is…
a) an induced ovulator
b) a spontaneous ovulator
a) an induced ovulator
(Occasionally she can also spontaneously ovulate)
The queen is an induced ovulator. This means that in the absence of stimulation…
- In the absence of stimulation, ovulation does not occur
- In the absence of ovulation, there is regression of the follicles
What does the blue line on this graph illustrate?
LH concentrations from mating must exceed a theshold to induce ovulation in the queen.
* There are individual differences between queens
* There is variation in the magnitude of LH surge on different days of the cycle (greatest response = mid-oestrus)
* Fortunately, there is summation of LH surges when these occur close to each other (frequent matings)
What is the typical inter-oestrus interval in the queen?
- 16-21 days
True/false: measuring progesterone is a good way to assess whether a queen has ovulated, because if she hasn’t ovulated, the follicle will regress and she will enter the luteal phase.
False
If she doesn’t ovulate, the follicle will regress but there is no luteal phase.
Therefore, progesterone will only rise if the queen ovulates.
What is the best way to try to ensure ovulation occurs when a queen is mated?
Ovulation occurs if:
* There is stimulation of the female (perineal/vaginal)
* Frequent mating occurs within a short period of time (3 matings within 12hrs)
* Matings occur on the second or third day of oestrus
Describe the length of the luteal phase in each of these 3 scenarios:
a) the queen is mated by does not ovulate
b) the queen is mated, ovulates, but does not fall pregnant
c) the queen is mated, ovulates, and becomes pregnant
a) no ovulation = no luteal phase
b) ovulation but no pregnancy = long luteal phase of approx. 45 days (pseudopregnant)
c) ovulation and pregnancy = luteal phase approx. 68 days
In which species are the ovulated occytes immature?
Bitch
What methods could we use to determine the optimal time to breed a bitch?
- Detecton of ovulation by ultrasound (v hard)
- Measurement of hormone changes -> look for a rise in progesterone to show approaching ovulation
- Indirect assessment of hormones: cytology, vaginoscopy, behaviour, vulval swelling
When is the optimal day in the cycle to breed a bitch?
Very variable = day 5 to day 30
Many breeders say day 10-12
In the bitch, the ovulated occyte is less mature than in other species. What relevance does this have for time of mating/fertilisation period?
Fertilisation period = 2 days before and 5 days after ovulation
Describe how the fertilisation window in dogs affects the apparent pregnancy length
- Late mating = apparent short pregnancy
- Early mating (at the start of the fertile period) = apparent long pregnancy
