Breeding & pregnancy diagnosis Flashcards
Why is the absence of oestrus not always a reliable pregnancy indicator?
Some animals may not return to oestrus due to dioestrus ovulation
Dams with young offspring may suppress oestrous signs due to protective behaviour
Oestrus-like signs can sometimes occur during pregnancy, esp in later stages
What are the key approaches to diagnosing pregnancy?
Absence of oestrus after mating (except in bitches)
Protein/endocrinological changes
Detection of fetus or fetal membranes
Physical changes in the dam (e.g. uterine enlargement & uterine artery)
Detection of maternal changes secondary to endocrinological changes (e.g. absence of oestrus, change in cervical mucus, vaginal wall thinning)
What hormonal markers indicate pregnancy?
Pregnancy-associated glycoproteins (species-specific)
Progesterone (sustained levels post-mating)
Placental oestrogens (measurable in urine or blood)
Relaxin (used in bitches & queens)
Equine chorionic gonadotropin (eCG) (mares)
How can the fetus or fetal membranes be detected?
Ultrasound examination
Rectal palpation
Radiographic examination
Abdominal palpation
Label the mare hormonal profile
What are the major hormonal changes during pregnancy in mares?
- Early pregnancy: Primary corpus luteum (CL) produces progesterone
- Day 35-40: Endometrial cups form, secreting eCG, which stimulates secondary CLs
- Day 100-120: Placenta takes over progesterone production, leading to decline in CL-derived progesterone
- Late pregnancy: Oestrogen increases, supporting fetal growth & placental development
What is the earliest day at which you can detect pregnancy in mare via ultrasound?
Day 12
What is the earliest day at which you can detect pregnancy in bitch via ultrasound?
Day 18 but more commonly from day 28
How does the oestrous cycle differ in pregnant and non-pregnant bitches?
There is no difference in progesterone profile between pregnant & non-pregnant bitches, making progesterone unreliable marker for pregnancy
What is the most reliable hormonal indicator of pregnancy in bitches?
Relaxin, which increases significantly in pregnancy & can be detected from day 25 post-mating
From what day can you see fetal mineralisation in bitches via radiography?
Day 45
How is Pregnancy diagnosed in cows?
Failure to return to oestrus (day 18-24)
Transrectal ultrasound (day 28)
Transrectal palpation (day 35)
Membrane slip (palpation) (day 35-90)
Ballottement of fetus (day 50)
Transrectal palpation of caruncles/cotyledons (day 80)
Transrectal uterine artery fremitus (day 105-210)
What is the best PD method in cows for:
1. Early testing
2. Positive diagnosis accuracy
3. Negative diagnosis accuracy
- Milk progesterone
- Transrectal ultrasound
- Transrectal ultrasound & rectal palpation
How is Pregnancy diagnosed in ewes?
Failure to be raddled (day 16-19)
Transabdominal ultrasound (day 30)
- Detection of fluid filled uterine horn
- Later detection of cotyledons/caruncles
- Slightly later examination increases accuracy & enables determination of no. of fetuses
How is Pregnancy diagnosed in sows?
Failure to return to oestrus (day 18-24)
Transabdominal B-mode ultrasound (day 20)
- Detection of fluid filled uterine horn
- Later detection of embryo
How is Pregnancy diagnosed in mares?
Transrectal ultrasound (day 12)
Transrectal palpation (day 21)
Plasma eCG (day 60-120)
Transrectal fetal ballottement (day 80)
How is Pregnancy diagnosed in bitches & queens?
Transabdominal ultrasound (day 25)
Plasma relaxin (day 25)
How does pregnancy diagnosis protocol vary in production systems?
Cows: Ultrasound 4 weeks post-AI for early detection
Mares: Stud management requires ultrasound at days 14, 21 & 35 post-mating
What is oestrus and how is it detected?
Oestrus: Period when female is sexually receptive to male
Key signs: Pro-oestrus precedes it; classic sign is standing to be mated
Timing: Varies by species in length, intensity & ovulation timing
When does oestrus occur in females?
After puberty
After parturition or lactational anoestrus
After seasonal anoestrus
During late follicular phase, driven by rising oestradiol
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?
Male factors:
- High-value males may be introduced at a specific time
- Controlled mating/artificial insemination requires oestrus monitoring
Female factors:
- 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
No commercial kits available for routine clinical use
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
In horses & high-value cattle, precise monitoring helps time breeding optimally
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
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
How do plasma progesterone and anuclear cells change around the LH surge in bitches?
Before LH surge:
- Low progesterone, increasing anuclear (cornified) cells.
At ovulation (~2 days post-LH surge):
- Progesterone rises sharply due to luteinisation
- Anuclear cells peak, indicating optimal mating time
After ovulation (~7 days post-LH surge):
- Progesterone remains high, supporting pregnancy
- Cornified cells decline, neutrophils may appear (metoestrus)
How do oestrogen and progesterone affect the vaginal epithelium?
Oestrogen (Proestrus & Early Oestrus):
- Thickens vaginal mucosa → keratinised squamous epithelium (protects against mating trauma)
- Increases oedema, causing red to pink/white mucosa
- Leakage of RBCs (serosanguinous discharge) seen in early proestrus
Progesterone (Post-LH Surge & Luteal Phase):
- Reduces oedema
- Causes mucosal shrinkage & wrinkling
- Leads to shedding of epithelial surface at end of fertile period
