Lecture 2 Flashcards
What is the purpose of pregnancy diagnosis in the mare
- To confirm pregnancy
- Distinguish between single and multiple conceptus
- Detect early embryonic death and manage a return to oestrus where early embryonic death is recorded
What are the methods of pregnancy diagnosis in the mare
- Behavioural assessment
- Lab tests
- Rectal palpation
- Ultrasonogrpahy
- Abdominal ballottement
- Oberservation - udder, change in shape of abdomen
What does behavioural assessment indicate
- Non-specific indicator of pregnancy
- Mares normally return to oestrus 16-20 days post ovulation
What does failure to return to oestrus indicate
Pregnancy
Behavioural assessment: false positive
Persistent luteal function, early embryonic death, failure to show signs of oestrus, anoestrus
Behavioural assessment: false negatives
Some pregnant mares can show behavioural signs of oestrus
What is a tease negative
Tease out - mare is visibly resistant to stallion
What is tease neutral
Passive - mare is indifferent/passive in presence of stallion
What is tease positive
Tease in - mare is interested in stallion; may urinate; wink vulva, squat, lean into stallion
What is the vaginal speculum examination
Examination of cervix 18-21 days after ovulation. It is non-specific indicator of pregnancy
What does a high, dry, tight and white cervix suggest
Dioestrus
What is progesterone produced by
CL
What do you collect with lab test and when
Test milk or plasma at time of expected return to oestrus
What do high concentrations indicate of progesterone
Presence of CL
How do you get a false negative with lab tests
Persistent CL function, embryonic death
When is equine chorionic gonadotrophin first produced by
Endometrial cups from days 36-40 of gestation
How long is equine chorionic gonadotrophin secreted for
up to 120 days of gestation
When do chorionic girdle cells develop around
25 days of gestation
When can cells from the chorionic girdle invade the endometrium
35 days
eCG - how you get a false positive
Foetal death occurs after endometrial cups have formed
eCG - how you get a false negative
Testing outside of the range of normal time for eCG production - sample taken too early
Explain Oestrgens of horse
Concentrations rise after day 60, peak at by 180 to 240 and then decline until parturition
What do oestrogen’s produce
Foetal-placental unit
What does a positive test of oestrogens indicate
Viable foetal-placental unit, so it can be test for foetal viability
How can you measure oestrogens
Serum, faeces and urine
What to test serum for
Oestrone sulphate
What to test urine for
Cuboni test. May not be used by many labs
What are the common times for pregnancy diagnosis
12-18: days after ovulation
24-30: detect normal growth rate, heartbeat, confirm single conceptus
45 - Confirm normal development
60 - Most pregnancy loss occurs before 60 so reconfirmation at or after Day 60 is advisable
120 - Conformation of pregnancy to enable management strategies to be developed
What is required before performing a rectal palpation
- Understanding of the breed
- Owner consent
- Good restraint
- Remove all faecal material before beginning examination
What technique is required for rectal palpation
- Dont rush
- Use lube
- Place hand cranial to the structure to be palpated before moving caudally onto the structure
- Do not palpate during peristaltic waves
- If straining persists consider the use of a twitch, anticholinergic drug Propanthelene bromide (Propan B) or Buscopan IV or intarectal lignocaine infusion can facilitate rectal relaxation
Rectal examination on horse: day 18-20
Increased tone, easier to palpate the outline of the uterus
- Prominent, firm cervix, feels like a pencil
- Transrectal ultrasound is needed to confirm diagnosis
Rectal examination on horse: day 25-30
- Prominent uterine tone and outline
- Palpably elongated cervix
- Small bulge palpated on ventral aspect of uterine horn close to bifurcation
- Thinning of the uterine wall, milk fluctuation detected particularly on the ventral aspect of the bulge
- False positive - large uterus with low tone
Rectal examination on horse: day 35-40
Prominent uterine tine and outline
Palpably long cervix
Spherical bulge, tennis ball/lemon palpable at the base of uterine horn
Rectal examination on horse: day 45-50
Increased uterine tone, prominent cervix, softball/grapefruit sized swelling at the base of uterine horn
Rectal examination on horse: day 60-65
Progressive filling of uterus with fluid results in less tone
Bulge associated with pregnancy located closer to the body of the uterus
Size of rockmelon
Rectal examination on horse: day 100-120
Bulge volleyball or basketball size
Need to trace swelling back to cervix or the ovaries to differentiate from fluid pilled bladder
Cranial margin of uterus cannot be felt
Ballottement of the foetus is sometimes possible
Rectal examination on horse: day 150-210
Ovaries drawn into a more media-ventral location as the heavy, descending uterus pulls on the broad ligament
Cannot palpate the full extremities of the uterus due to larger size
Foetus usually palpable by ballottement
Rectal examination on horse: day 240 - term
Foetus is easier to palpate but can be difficult to precisely age by palpation
Foetal dimensions e.g. eye socket diameter/circumference can be used to estimate age of foetus
When doing rectal palpation what is the size to look for in the mare
28d - hens egg
35d- lemon
42d - orange
49d - softball/grape
56d - cantaloupe/rockmellon
by 90d - it is hard to delineate the cranial margin of uterus
Foetal ballottement per rectum becomes consistent after 150d
List the advantages of transrectal ultrasonography
- Early pregnancy diagnosis
- Diagnosis of multiple foetuses - note that in mares if a twin is detected, early embryonic reduction of one twin is preferred due to <15% of twin pregnancies surviving to term and if they do, many surviving twins will be weak
- Uterine pathology
- Determine stages of gestation, foetal sex, foetal viability
- Assess postpartum uterine involution
- Ovarian cyclic status and ovulation rate
- Stage of the oestrus cycle
Ovarian pathology
What is the aim of using an ultrasound to diagnose pregnancy at 14-16 days
Diagnose pregnancy and to detect twin pregnancies if present
Why must the whole track be checked with an ultrasound at 14-16 days
Conceptuses are mobile
Twin pregnancies - wait for conceptuses to separate or separate conceptuses and crush smaller one
Why must you use an ultrasound at 21-22 days pf pregnancy
- Confirm pregnancy diagnosis and presence of a singleton
- Distinguish embryos form uterine cysts
Why must you use an ultrasound at 24 days pf pregnancy
- A heartbeat within the embryo becomes detectable
- Identification
Why must you use an ultrasound at 35 days pf pregnancy
Confirm diagnosis, verify viability before endometrial cups are formed and eCG is produced
What can endometrial cysts can be confused with
Early pregnancy
What are the ultrasound land marks (size and shape of embryonic vesicle)
12-14d - spherical vesicle visible
16d vesicle fixation
20-21d embryo proper visible
24-26d - Heartbeat visible
28d embryo located at centre of vesicle
36d embryo located at the top of vesicle
47d embryo positioned near the bottom of the vesicle
