Fertility and breeding time in the female Flashcards
What is oestrus?
period where female is sexually receptive to male
What is the classic sign of oestrus?
Pro-oestrus precedes it; classic sign is standing to be mated
When does oestrus occur?
After puberty
After parturition and/or lactational anoestrus
After seasonal anoestrus
During late follicular phase, driven by increasing oestradiol conc
To what species does this hormonal profile belong?
ewe, cow, sow
To what species does this hormonal profile belong?
Mare
To what species does this hormonal profile belong?
Bitch
How does the timing of ovulation vary across species?
Ewe, Cow, Sow: Ovulation occurs after oestrus ends
Mare: Ovulation occurs towards end of oestrus
Bitch: Ovulation occurs several days after oestrus begins
What factors affect the optimal time to mate in males?
- High-value males may be introduced at a specific time
- Controlled mating/artificial insemination requires oestrus monitoring
What factors affect the optimal time to mate in females?
- Requires pre-ovulatory follicle growth
- Oestrus doesn’t always predict ovulation timing
- Oocytes are short-lived (<1 day) in most species (days bitch)
What is the difference between the fertilisation period and the fertile period?
Fertilisation period: When oocytes are available for fertilisation (hours to days depending on species)
Fertile period: broader window where mating can result in pregnancy
What tools are used to determine the best breeding time?
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
How does progesterone indicate oestrus and ovulation timing?
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
What is the role of oestradiol in predicting ovulation?
Elevated during follicular phase, often mirroring oestrus
(Only used in research setting)
What is the role of GnRH in ovulation?
GnRH surge triggers LH release, leading to ovulation
Has a short-lived effect
How is LH used to predict ovulation?
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
How does the reproductive tract feel under oestrogen dominance (during oestrus) in mare and cow?
Mare:
- Broad & soft cervix
- Large, oedematous (soft) uterus
Cow:
- Narrow & tense cervix
- Oedematous uterus with increased tone
How does the reproductive tract feel under progesterone dominance in mare and cow?
Mare:
- Hard & narrow cervix
- Small uterus with increased tone
Cow:
- Flaccid and soft cervix
- Flaccid uterus with reduced tone
Why is it important to check for the corpus luteum (CL) on ultrasound?
Active CL means high progesterone, preventing ovulation
If regressing, it becomes smaller with increased echogenicity
What are the typical follicular sizes for ovulation in different species?
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
How does follicular morphology change before ovulation?
Follicle loses turgidity & becomes irregular in shape
Mare-specific: follicular wall thickens (luteinisation) before ovulation
Why is vaginal cytology used in dogs?
Helps determine oestrous stage by analysing vaginal epithelial & blood cells
Used alongside progesterone testing to optimise mating time
How do vaginal cells change during the oestrous cycle in the bitch?
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
Label this vaginal cytology - what stage of cycle is this dog in?
How can ovulation be induced for controlled breeding?
GnRH: Induces LH surge → ovulation within ~1 day
hCG: Mimics LH, directly triggering ovulation
OvSynch protocol (cattle): Synchronises ovulation for timed AI
When is the optimal time for mating in the bitch?
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)
What phase of the oestrus cycle is this?
Anoestrus: Small parabasal cells, majority of cells are circular, occasional neutrophils
What phase of the oestrus cycle is this?
Proestrus: Small intermediate cells, majority of cells are irregular in shape, large number of RBCs, occasional neutrophils
What phase of the oestrus cycle is this?
Oestrus: Large intermediate and anuclear cornified cells, irregular shaped cells, some RBCs, no neutrophils
What phase of the oestrus cycle is this?
Metoestrus: Return of neutrophils, fewer cornified cells
What hormone is responsible for vaginal mucosa thickening in proestrus?
Oestrogen – It causes proliferation, oedema, and keratinisation of the vaginal epithelium.
What is the appearance of the vaginal mucosa during early proestrus?
Thickened, oedematous, and red with visible blood vessels. Serosanguinous discharge may be present.
What marks the transition from proestrus to oestrus?
Decline in oestrogen and a rise in progesterone, triggering the LH surge and ovulation.
What happens to the vaginal epithelium during oestrus?
Oedema reduces, mucosal folds shrink, and the epithelium appears pale (cream/white), dry, and wrinkled.
How does the vaginal epithelium change at the end of the fertile period?
Epithelial shedding occurs rapidly (~48h), with mucosa appearing flaccid and mixed white/red in color.
What happens to the vaginal lumen as the luteal phase progresses?
The lumen narrows, mucosa takes on a rosette appearance, and ultimately becomes flat, dry, and red, similar to anoestrus.
What are the phases of the vaginal mucosa during the oestrus cycle?
Inactive phase
Oedematous phase
Shrinkage phase
Angulated phase
Declining phase
What are the characteristics of the Inactive Phase (I) of the vaginal mucosa?
Thin, red, dry mucosa with low, flattened folds.
What happens to the vaginal mucosa in the Oedematous Phase (O)?
Mucosa becomes thickened, swollen, grey/white, with rounded, turgid folds.
How does the Shrinkage Phase (S) of the vaginal mucosa differ from the Oedematous Phase?
Mucosa remains thickened and white but starts to lose turgidity, showing wrinkling and furrowing, yet folds remain rounded.
S1: Early shrinkage
S2: Advanced shrinkage
What marks the transition from the Shrinkage Phase to the Angulated Phase of the vaginal mucosa?
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
What happens in the Declining Phase (D) of the vaginal mucosa?
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
What happens after the Declining Phase (D) of the vaginal mucosa?
The cycle returns to the Inactive Phase (I) with thin, red, dry mucosa and more debris than before.
