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Equine reproduction > Equine breeding facts > Flashcards

Equine breeding facts 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
Q

Timing of insemination with different semen storage methods

A

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)

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26
Q

When to recover embryo for transfer

A

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

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27
Q

What is the Wilsher method for embryo transfer

A

Grabbing cervix and pulling it to vulval level
- Allows visualisation during embryo transfer

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28
Q

Why can’t we get superovulation in horses

A

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

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29
Q

Why can’t you do embryo transfer from a larger mare to a smaller one

A

Very high risk of placental insufficiency

30
Q

What type of placenta does a horse have

A

Diffuse epithelio-chorial
= 6 layers (max)

31
Q

Timing of conceptus movement and implantation

A

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
Q

Progesterone provision during early pregnancy

A

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
Q

Timing of ultrasound scans post-cover

A

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
Q

Dealing with twins

A

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
Q

Gestation length of pony

A

315-340 days

36
Q

Gestation length of TB

A

320-360 days

37
Q

Gestation length of donkey

A

360-380 days

38
Q

Advantage of using transabdominal US scan vs trans-rectal to look at placenta

A

Can see corrugated edge of chorioallantois to check for detachment

39
Q

Fetal position from 7 months gestation until labour

A

Cranial, ventral, flexed

40
Q

Fetal position just before labour (moves into this during stage 1)

A

Cranial, dorsal, extended

41
Q

Mammary secretion electrolytes when approaching parturition

A

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
Q

Blood progesterone changes in lead up to labour

A

Rises from around 300 days
Then crashes 2-3 days before birth

43
Q

First stage labour in a horse

A

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
Q

Second stage labour in a horse

A

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
Q

Third stage labour in a horse

A

Placenta expelled within 30 mins - 2 hours

46
Q

How should placenta come out after birth

A

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
Q

What is a hippomane

A

brown thing in allantoic sac made of urate crystals and dandruff

48
Q

What does it mean if amnion is yellow instead of silver/grey

A

Meconium staining due to fetal distress

49
Q

What does a pale stripe on chorioallantois from cervical star upwards mean

A

Ascending placentitis from cervix up e.g due to poor perineal conformation or infection from penis

50
Q

What if we see placentitis in the top half of horn not tracking from cervix

A

Haematogneous spread
Expect foal to be dysmature due to less nutrition + higher infection risk

51
Q

Which areas of placenta are often pale i.e no microvilli

A

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
Q

TB terminology for full term, premature, abortion

A

Full term = >320 days gestation
Premature = 300-320 days
Abortion = <300 days gestation

53
Q

What does dysmature mean

A

Foal born full term (>320 days) BUT with signs of prematurity

54
Q

Signs of prematurity in a foal

A

Domed, forehead, soft coat, low birthweight, lax joints

55
Q

Treating a foal umbilical cord

A

0.5% chlorhexidine
Or 2% iodine

56
Q

High, moderate and low risk foals

A

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
Q

When would we give TAT to foals

A

If we don’t know colostral IgG levels
Or mare unvaccinated?/

58
Q

What can we do on a day 2 examination of the foal

A

Routine haematology and serum protein levels
- Can measure level of IgG + check for organ dysmaturity

59
Q

What level of serum IgG do we want in a 2 day foal

A

Ideally >8g/L (insurance cut off usually 4)

60
Q

What qualifies and partial and total failure of passive transfer

A

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
Q

What does neutrophil:lymphocyte ratio on day 2 haematology tell us about foal

A

Should be 2:1 if mature
- If reversed with more lymphocytes = sign of prematurity

62
Q

Serum amyloid A vs fibrinogen measurements in day 2 foal

A

SAA = more useful; short half life so indicates inflammatory problem NOW

Fibrinogen has longer half life; could reflect past placentitis during pregnancy

63
Q

What MCV do we want in a 2 day old foal

A

<40
if higher suggests dys/prematurity

64
Q

IgG uptake timings in foal

A

Max uptake via pinocytosis during first 8 hours
Some lesser uptake up to 36 hours

65
Q

What qualities do we want in good colostrum

A

Yellow and viscous
IgG levels >50g/L (or >20% sugar refractometer reading)

NB: for donor colostrum should be >70g/L IgG

66
Q

Which horses can NOT donate colostrum

A

Those which have given birth to haemolytic foals
Maiden or >15yo mares

67
Q

Day 3 foal exam for insurance exam also includes…

A

opthalmoscope

68
Q

When do we wean foals

A

~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
Q

Candidates for fostering an orphan foal onto

A

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
Q

What hormone do we test for to check for testicular tissue i.e in differentiating true vs false rig

A

Anti-MH hormone
- If elevated shows testicular tissue present

71
Q

By what point should foals have passed meconium

A

4 hours

Equine reproduction (3 decks)

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