16.8.1: Introduction to repro week and cyclicity in the bitch and queen

Question 1

The bitch is
* Polyoestrus
* Monoestrus

Answer 1

Monoestrus
Oestrus is followed by an anoestrus phase (lasting approx. 7 months)

Question 2

Which is the main luteotrophic hormone in the bitch?

Answer 2

Prolactin
This hormone supports and maintains the function of CL

Question 3

What happens if you give a prolactin inhibitor to a pregnant bitch?

Answer 3

• Prolactin inhibitor removes support for CL
• Progesterone falls
• Abortion occurs

Question 4

What is it important to establish before giving prolactin inhibitor to a bitch with pseudopregnancy?

Answer 4

That the bitch is not pregnant - if she is, prolactin inhibitor will cause abortion.

Question 5

What is the role of prolactin in the bitch?

Answer 5

• Main luteotrophic hormone
• From Day 21 progesterone concentrations decline
• This decline stimulates a rise in prolactin which supports and maintains the CL

Question 6

Where is progesterone produced during pregnancy in the bitch and why does this matter?

Answer 6

Progesterone is only produced in the ovary
* Ovariectomy at any stage of pregnancy will result in pregnancy loss

Question 7

How can we terminate the luteal phase in the bitch?

Answer 7

Repeated administration of a prolactin inhibitor (e.g. cabergoline a.k.a. Galastop) from Day 21 in cycle onwards

Question 8

Which species are represented with the progesterone graphs here?

Answer 8

• Top - cow - non-seasonal polyoestrus
• Bottom - dog - monoestrus

Both are non-pregnant

Question 9

A bitch with mammary gland enlargement is likely to be in which phase of the cycle?

Answer 9

Luteal phase

Question 10

How should you judge if a cell on cytology is big or small?

Answer 10

Assess nuclear to cytoplasmic ratio

Question 11

Key feature of the luteal phase on vaginal cytology

Answer 11

Return of neutrophils

Question 12

1

Answer 12

GnRH

Question 13

2

Answer 13

FSH

Question 14

3

Answer 14

LH

Question 15

Surge in which hormone triggers ovulation?

Answer 15

LH

Question 16

This image shows the oestrus cycle of which species?

Answer 16

Dog

Question 17

What is the inter-oestrus interval in the bitch?
a) 9 months
b) 7 months
c) 6 months
d) 11 months

Answer 17

b) 7 months

Question 18

The bitch is…
a) an induced ovulator
b) an spontaneous ovulator

Answer 18

b) an spontaneous ovulator

Question 19

Polyoestrus

Answer 19

One oestrus cycle follows the other without a period of anoestrus.
e.g. in the cow
The bitch is monoestrus

Question 20

What does this graph show regarding the progesterone profiles of the pregnant and non-pregnant bitch?

Answer 20

The progesterone profiles of the pregnant and non-pregnant bitch are very similar (slightly higher concentration in the pregnant animal)

Question 21

Explain the indicated section of the graph and the change in hormone concentration shown here

Answer 21

The spikes in prolactin as associated with lactation

Question 22

What happens if you give a prolactin inhibitor to the pregnant bitch at the time indicated by the star?

Answer 22

• 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

Question 23

Progesterone is produced by which structures in the bitch and queen?
a) placenta
b) ovary
c) both
d) neither

Answer 23

b) ovary only
This means ovariectomy/loss of support for the CL at any stage during pregnancy will result in pregnancy loss.

Question 24

Which hormones would you expect to be elevated in the non-pregnant bitch? What effect would these have?

Answer 24

• Elevated progesterone -> mammary enlargment, potential for milk secretion
• Elevated prolactin -> milk production, behavioural changes typical of pregnancy

Question 25

This graph shows progesterone concentrations in the non-pregnant animal of which species?

Answer 25

Dog

Question 26

Which species?

Answer 26

Cow

Question 27

Which species?

Answer 27

Ewe

Question 28

Which species?

Answer 28

Mare

Question 29

Which species?

Answer 29

Bitch

Question 30

Which species?

Answer 30

Queen

Question 31

How does season of birth impact the age a female kitten will be when they enter puberty?

Answer 31

* 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)

Question 32

The queen is... a) an induced ovulator b) a spontaneous ovulator

Answer 32

a) an induced ovulator (Occasionally she can also spontaneously ovulate)

Question 33

The queen is an induced ovulator. This means that in the absence of stimulation...

Answer 33

* In the absence of stimulation, ovulation does not occur * In the absence of ovulation, there is regression of the follicles

Question 34

What does the blue line on this graph illustrate?

Answer 34

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)

Question 35

What is the typical inter-oestrus interval in the queen?

Answer 35

* 16-21 days

Question 36

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.

Answer 36

**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.

Question 37

What is the best way to try to ensure ovulation occurs when a queen is mated?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

In which species are the ovulated occytes immature?

Answer 39

Bitch

Question 40

What methods could we use to determine the optimal time to breed a bitch?

Answer 40

* 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

Question 41

When is the optimal day in the cycle to breed a bitch?

Answer 41

Very variable = day 5 to day 30 Many breeders say day 10-12

Question 42

In the bitch, the ovulated occyte is less mature than in other species. What relevance does this have for time of mating/fertilisation period?

Answer 42

**Fertilisation period = 2 days before and 5 days after ovulation**

Question 43

Describe how the fertilisation window in dogs affects the apparent pregnancy length

Answer 43

* Late mating = apparent short pregnancy * Early mating (at the start of the fertile period) = apparent long pregnancy