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Equine reproduction > Equine breeding facts COPY > Flashcards

Equine breeding facts COPY Flashcards

1
Q

Hormonal changes from anoestrus to oestrus

A

With increasing day length get less melatonin secretion
This releases inhibition on the hypothalamus
-> More GnRH release
–> Stimulates FSH and LH release from pituitary
–> FSH stimulates follicular growth; these make oestrogen which stimulates more LH production (also make inhibin to ensure just one follicle becomes dominant)
–> LH surge and ovulation
Then: progesterone from CL stops cycling by inhibiting LH secretion

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2
Q

What is shortened dioestrus

A

When mares return to oestrus every 10-12 days due to short CL lifespan

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3
Q

What does ‘snow-storm’ ultra sound on ovary mean

A

Anovulatory follicles with haemorrhage into them

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4
Q

Treating transitional/spring oestrus

A

Shut system down using progesterone or P + oestradiol
then use luteolytic
–> Get rebound from -ve feedback so larger LH surge and oestrus

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5
Q

Requirements for short-cycling a mare in dioestrus to get to oestrus

A

CL should be >5 days old
- Then give prostaglandins
- Expect ovulation in 8-10 days

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6
Q

How would hCG injection stop mares coming into oestrus

A

Acts like LH and will cause induction of ovulation from pre-ovulatory size follicle

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7
Q

How long can mares compete when pregnant

A

Until 120 days gestation

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8
Q

Cycle length in mares

A

21-23 days
Luteal phase (dioestrus) = 14-15 days
Oestrus = 4-7 days

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9
Q

What are the 3 venereal diseases we screen against

A
  • Taylorella equigenitalis
  • Pseudomonas aeruginosa
  • Klebsiella pneumonia
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10
Q

Indications for performing a Caslick’s operation

A

Poor perineal conformation
- If vulval lips don’t make a tight seal
- If pelvic bony shelf not at top of vulval opening; should suture from top down the bony shelf

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11
Q

Changes on ultrasound of ovary leading up to oestrus/ovulation

A
  • Orange segment appearance (classic sign of approaching oestrus)
    –> Then decreases in 24hrs pre-oestrus
  • Before ovulation, dominant follicle becomes more triangular to ovulate out of fossa
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12
Q

How can we check ovulation has occurred on ultrasound post-cover

A

Follicle should now be hard and hyperechoic (instead of soft and anechoic) because now a CL

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13
Q

Histological changes in chronic endometrial disease (endometrosis)

A

1) Glands cluster together to form glandular nests
2) Improper drainage causes excessive lymphatic lacunae

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14
Q

Viability times of sperm vs egg

A

Sperm: 72 hours
Ovum: 12-24 hours (= limiting factor)

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15
Q

Orientation of stallion testes

A

Horizontal
Head of epididymis cranial
Can rotate up to 180 degrees without issues

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16
Q

Normal scrotal size

A

10cm length
5cm width

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17
Q

True rig vs false rig

A

True rig = incompletely castrated; so cryptorchid with retained testicle so still have androgens causing libido

False rig = correctly castrated - libido is psychological

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18
Q

Swabs for venereal diseases in stallion

A

Penile sheath, urethra, urethral fossa, pre-ejaculatory fluid

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19
Q

Normal sperm pH

A

7.2-7.6

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20
Q

Ideal sperm total motility and progressive motility

A

Total: 75-90%
Progressive: 55-80%

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21
Q

What should morphologically normal, progressively motile sperm concentration be in second ejaculate

A

> 1.5 x 10^9
With ~50% of number vs the first ejaculate from an hour earler

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22
Q

Primary abnormalities of sperm morphology

A

Occurs in testicular parenchyma
e.g misshapen heads, bent midpieces, missing head/tail, acrosome knobbing

Should be <20%

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23
Q

Secondary abnormalities of sperm morphology

A

Occurs in epididymus in maturation phase
e,g retained protoplasmic droplet = sign of overuse

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24
Q

What does coiled tails in sperm suggest

A

Cold shock = artefact

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25
Timing of insemination with different semen storage methods
Fresh: up to 48 hours pre-ovulation Chilled: up to 24 hours pre-ovulation (but 12 better) Frozen: 6 hours either side of ovulation (may want to wait to check it has happened since expensive)
26
When to recover embryo for transfer
Routinely: day 7/8 which is blastocyst stage May do on day 6: for freezing or splitting for twins (before ICM develops) BUT lower recovery as may still be in fallopian tube
27
What is the Wilsher method for embryo transfer
Grabbing cervix and pulling it to vulval level - Allows visualisation during embryo transfer
28
Why can't we get superovulation in horses
Because ovary in kidney bean shaped with specific ovulation fossa with thin tunica albuginea = only spot where ovulation can occur + follicles inhibit each other via inhibin so just one becomes dominant --> Can't harvest lots of eggs
29
Why can't you do embryo transfer from a larger mare to a smaller one
Very high risk of placental insufficiency
30
What type of placenta does a horse have
Diffuse epithelio-chorial = 6 layers (max)
31
Timing of conceptus movement and implantation
Days 0-6: fertilised ova stays in fallopian tube - From day 4-5, secretes PGE2 which causes oviduct spincter to relax and allow entrance to uterus Days 6-16: blastocyst is highly motile in uterus lumen and must signal to mare not to produce PGF2alpha (via movement and oes secretion?) Day 18: increase in uterine tone causing fixing of blastocyst at base of horn True implantation at day 40-42 when microvillous attachment of trophoblast to endometrial epithelium
32
Progesterone provision during early pregnancy
CL decreases P secretion from around day 16 -> Day 35: chorionic girdle cells from fetal trophoblast invade endometrium and form endometrial cups --> These secrete eCG which travels in bloodstream and causing ovarues to produce accessory CLs (from this point rare to lose pregnancy) From day 80, placenta starts to take over
33
Timing of ultrasound scans post-cover
Day 16: allows early diagnosis + easy dealing with twins if detected Day 30: can spot failing pregnancies, double check for twins Day 46: rare to lose after this since endometrial cups formed already (day 35)
34
Dealing with twins
Before day 20: pop one conceptus After day 35: use needle to draw out. allantoic fluid from one Then by day 90; flops over pelvic brim --> So inject potassium chloride into one heart
35
Gestation length of pony
315-340 days
36
Gestation length of TB
320-360 days
37
Gestation length of donkey
360-380 days
38
Advantage of using transabdominal US scan vs trans-rectal to look at placenta
Can see corrugated edge of chorioallantois to check for detachment
39
Fetal position from 7 months gestation until labour
Cranial, ventral, flexed
40
Fetal position just before labour (moves into this during stage 1)
Cranial, dorsal, extended
41
Mammary secretion electrolytes when approaching parturition
In lead up, Na+ crashes and K+ rises - Where they cross means 48 hours until birth Ca2+ spikes just before labour; rise means 12-24 hours until birth
42
Blood progesterone changes in lead up to labour
Rises from around 300 days Then crashes 2-3 days before birth
43
First stage labour in a horse
Begins with myometrial contractions Usually 2-6 hours (longer in maidens) Get cervical dilation, vulva relaxation, movement of fetus into cranial, dorsal, extended position
44
Second stage labour in a horse
Starts with abdominal contractions beginning Get rupture of chorioallantois at cervical star --> Allantois appears as yellow sac THEN foal should be out within 20 mins
45
Third stage labour in a horse
Placenta expelled within 30 mins - 2 hours
46
How should placenta come out after birth
Inside out i.e smooth allantoic side first and red velvet microvilli on inside --> Pulled inside out by umbilical cord as fetus moves through If it comes out the other day suggests separation before birth
47
What is a hippomane
brown thing in allantoic sac made of urate crystals and dandruff
48
What does it mean if amnion is yellow instead of silver/grey
Meconium staining due to fetal distress
49
What does a pale stripe on chorioallantois from cervical star upwards mean
Ascending placentitis from cervix up e.g due to poor perineal conformation or infection from penis
50
What if we see placentitis in the top half of horn not tracking from cervix
Haematogneous spread Expect foal to be dysmature due to less nutrition + higher infection risk
51
Which areas of placenta are often pale i.e no microvilli
Cervical star (so no nutrients from here) Tips of horns where papillae of fallopian tubes are Where endometrial cups were i.e at base of pregnant horn Sites of any endometrial cysts OR placentitis
52
TB terminology for full term, premature, abortion
Full term = >320 days gestation Premature = 300-320 days Abortion = <300 days gestation
53
What does dysmature mean
Foal born full term (>320 days) BUT with signs of prematurity
54
Signs of prematurity in a foal
Domed, forehead, soft coat, low birthweight, lax joints
55
Treating a foal umbilical cord
0.5% chlorhexidine Or 2% iodine
56
High, moderate and low risk foals
High: maternal disease, colostral loss, vulval discharge, twins, FPT, meconium stain, poor hygiene, low environmental exposure Moderate: just one factor of prenatal or foal origin Low: no risk factors
57
When would we give TAT to foals
If we don't know colostral IgG levels Or mare unvaccinated?/
58
What can we do on a day 2 examination of the foal
Routine haematology and serum protein levels - Can measure level of IgG + check for organ dysmaturity
59
What level of serum IgG do we want in a 2 day foal
Ideally >8g/L (insurance cut off usually 4)
60
What qualifies and partial and total failure of passive transfer
Partial = 2-4 g/L IgG in foal blood Total = <2g/L Will commonly give plasma transfusion if the serum IgG is <4g/L
61
What does neutrophil:lymphocyte ratio on day 2 haematology tell us about foal
Should be 2:1 if mature - If reversed with more lymphocytes = sign of prematurity
62
Serum amyloid A vs fibrinogen measurements in day 2 foal
SAA = more useful; short half life so indicates inflammatory problem NOW Fibrinogen has longer half life; could reflect past placentitis during pregnancy
63
What MCV do we want in a 2 day old foal
<40 if higher suggests dys/prematurity
64
IgG uptake timings in foal
Max uptake via pinocytosis during first 8 hours Some lesser uptake up to 36 hours
65
What qualities do we want in good colostrum
Yellow and viscous IgG levels >50g/L (or >20% sugar refractometer reading) NB: for donor colostrum should be >70g/L IgG
66
Which horses can NOT donate colostrum
Those which have given birth to haemolytic foals Maiden or >15yo mares
67
Day 3 foal exam for insurance exam also includes...
opthalmoscope
68
When do we wean foals
~6 months NB: don't do close to other stressful events e.g castrating, vaccinating etc For hand-reared; can do once they eat 1lb/month of age/day of grain creep
69
Candidates for fostering an orphan foal onto
Parturient nurse mare who lost foal OR can induce lactation in another mare; via dopamine antagonists etc Should be docile, multiparous Foal should be <3 weeks old
70
What hormone do we test for to check for testicular tissue i.e in differentiating true vs false rig
Anti-MH hormone - If elevated shows testicular tissue present
71
By what point should foals have passed meconium
4 hours

Equine reproduction (3 decks)

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