Fertility and breeding time in the female

Question 1

What is oestrus?

Answer 1

period where female is sexually receptive to male

Question 2

What is the classic sign of oestrus?

Answer 2

Pro-oestrus precedes it; classic sign is standing to be mated

Question 3

When does oestrus occur?

Answer 3

After puberty
After parturition and/or lactational anoestrus
After seasonal anoestrus
During late follicular phase, driven by increasing oestradiol conc

Question 4

To what species does this hormonal profile belong?

Answer 4

ewe, cow, sow

Question 5

To what species does this hormonal profile belong?

Answer 5

Mare

Question 6

To what species does this hormonal profile belong?

Answer 6

Bitch

Question 7

How does the timing of ovulation vary across species?

Answer 7

Ewe, Cow, Sow: Ovulation occurs after oestrus ends

Mare: Ovulation occurs towards end of oestrus

Bitch: Ovulation occurs several days after oestrus begins

Question 8

What factors affect the optimal time to mate in males?

Answer 8

• High-value males may be introduced at a specific time
• Controlled mating/artificial insemination requires oestrus monitoring

Question 9

What factors affect the optimal time to mate in females?

Answer 9

• Requires pre-ovulatory follicle growth
• Oestrus doesn’t always predict ovulation timing
• Oocytes are short-lived (<1 day) in most species (days bitch)

Question 10

What is the difference between the fertilisation period and the fertile period?

Answer 10

Fertilisation period: When oocytes are available for fertilisation (hours to days depending on species)

Fertile period: broader window where mating can result in pregnancy

Question 11

What tools are used to determine the best breeding time?

Answer 11

Hormone monitoring (progesterone, LH, oestradiol, GnRH)

Ultrasound to track ovarian structures

Rectal palpation (e.g. in cows, mares)

Vulval softening & vaginal cytology (dogs)

Pharmacological induction of ovulation

Question 12

How does progesterone indicate oestrus and ovulation timing?

Answer 12

Decreases after luteolysis, marking start of follicular phase

Must be low for oestrus to occur

In dogs, rising progesterone level indicates luteinisation, meaning ovulation is imminent

Question 13

What is the role of oestradiol in predicting ovulation?

Answer 13

Elevated during follicular phase, often mirroring oestrus

(Only used in research setting)

Question 14

What is the role of GnRH in ovulation?

Answer 14

GnRH surge triggers LH release, leading to ovulation

Has a short-lived effect

Question 15

How is LH used to predict ovulation?

Answer 15

LH surge directly triggers ovulation

Tightly regulated time frame from surge to ovulation

Commercial kits available for cats & dogs

Frequent sampling required, optimal window day 4-7 post-surge in dogs

Question 16

How does the reproductive tract feel under oestrogen dominance (during oestrus) in mare and cow?

Answer 16

Mare:
- Broad & soft cervix
- Large, oedematous (soft) uterus

Cow:
- Narrow & tense cervix
- Oedematous uterus with increased tone

Question 17

How does the reproductive tract feel under progesterone dominance in mare and cow?

Answer 17

Mare:
- Hard & narrow cervix
- Small uterus with increased tone

Cow:
- Flaccid and soft cervix
- Flaccid uterus with reduced tone

Question 18

Why is it important to check for the corpus luteum (CL) on ultrasound?

Answer 18

Active CL means high progesterone, preventing ovulation

If regressing, it becomes smaller with increased echogenicity

Question 19

What are the typical follicular sizes for ovulation in different species?

Answer 19

Cows: Follicle must be ≥10 mm, typically 16-20 mm. (>20 mm may indicate pathology)

Mares: Follicle typically reaches 30-50 mm before ovulation

Ovulation when follicle stops growing

Question 20

How does follicular morphology change before ovulation?

Answer 20

Follicle loses turgidity & becomes irregular in shape

Mare-specific: follicular wall thickens (luteinisation) before ovulation

Question 21

Why is vaginal cytology used in dogs?

Answer 21

Helps determine oestrous stage by analysing vaginal epithelial & blood cells

Used alongside progesterone testing to optimise mating time

Question 22

How do vaginal cells change during the oestrous cycle in the bitch?

Answer 22

Proestrus:
- Increasing epithelial layers under oestrogen influence
- RBCs present → responsible for bloody vaginal discharge

Oestrus:
- Large cornified (anuclear) cells appear
- Peak cornification = optimal mating time

Metoestrus:
- Influx of neutrophils → indicates ovulation has passed & it’s too late for mating

Question 23

Label this vaginal cytology - what stage of cycle is this dog in?

Answer 23

Question 24

How can ovulation be induced for controlled breeding?

Answer 24

GnRH: Induces LH surge → ovulation within ~1 day

hCG: Mimics LH, directly triggering ovulation

OvSynch protocol (cattle): Synchronises ovulation for timed AI

Question 25

When is the optimal time for mating in the bitch?

Answer 25

Peak fertility occurs 1d before to 5-6 days after LH surge Best determined by: - Plasma progesterone measurement (rises post-LH surge) - Vaginal cytology (≥80% cornified cells) - Serial LH measurement (daily testing needed)

Question 26

What phase of the oestrus cycle is this?

Answer 26

Anoestrus: Small parabasal cells, majority of cells are circular, occasional neutrophils

Question 27

What phase of the oestrus cycle is this?

Answer 27

Proestrus: Small intermediate cells, majority of cells are irregular in shape, large number of RBCs, occasional neutrophils

Question 28

What phase of the oestrus cycle is this?

Answer 28

Oestrus: Large intermediate and anuclear cornified cells, irregular shaped cells, some RBCs, no neutrophils

Question 29

What phase of the oestrus cycle is this?

Answer 29

Metoestrus: Return of neutrophils, fewer cornified cells

Question 30

What hormone is responsible for vaginal mucosa thickening in proestrus?

Answer 30

Oestrogen – It causes proliferation, oedema, and keratinisation of the vaginal epithelium.

Question 31

What is the appearance of the vaginal mucosa during early proestrus?

Answer 31

Thickened, oedematous, and red with visible blood vessels. Serosanguinous discharge may be present.

Question 32

What marks the transition from proestrus to oestrus?

Answer 32

Decline in oestrogen and a rise in progesterone, triggering the LH surge and ovulation.

Question 33

What happens to the vaginal epithelium during oestrus?

Answer 33

Oedema reduces, mucosal folds shrink, and the epithelium appears pale (cream/white), dry, and wrinkled.

Question 34

How does the vaginal epithelium change at the end of the fertile period?

Answer 34

Epithelial shedding occurs rapidly (~48h), with mucosa appearing flaccid and mixed white/red in color.

Question 35

What happens to the vaginal lumen as the luteal phase progresses?

Answer 35

The lumen narrows, mucosa takes on a rosette appearance, and ultimately becomes flat, dry, and red, similar to anoestrus.

Question 36

What are the phases of the vaginal mucosa during the oestrus cycle?

Answer 36

Inactive phase Oedematous phase Shrinkage phase Angulated phase Declining phase

Question 37

What are the characteristics of the Inactive Phase (I) of the vaginal mucosa?

Answer 37

Thin, red, dry mucosa with low, flattened folds.

Question 38

What happens to the vaginal mucosa in the Oedematous Phase (O)?

Answer 38

Mucosa becomes thickened, swollen, grey/white, with rounded, turgid folds.

Question 39

How does the Shrinkage Phase (S) of the vaginal mucosa differ from the Oedematous Phase?

Answer 39

Mucosa remains thickened and white but starts to lose turgidity, showing wrinkling and furrowing, yet folds remain rounded. S1: Early shrinkage S2: Advanced shrinkage

Question 40

What marks the transition from the Shrinkage Phase to the Angulated Phase of the vaginal mucosa?

Answer 40

In the Angulated Phase (A), the mucosal folds develop sharp, irregular peaks, and the tissue appears wrinkled and shrunken. A1: Early angulation A2 & A3: More pronounced peaks and shrinkage

Question 41

What happens in the Declining Phase (D) of the vaginal mucosa?

Answer 41

Mucosal folds progressively shrink and become flaccid, then rounded, followed by epithelial sloughing. Ends with a thin, variegated mucosa and rosette-like folds. D1: Flaccid folds D2: Rounded folds D3: Sloughing of epithelium D4: Rosette-like mucosa

Question 42

What happens after the Declining Phase (D) of the vaginal mucosa?

Answer 42

The cycle returns to the Inactive Phase (I) with thin, red, dry mucosa and more debris than before.