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Module 22: Reproduction & Fertility > Intro to Equine Pregnancy & Parturition > Flashcards

Intro to Equine Pregnancy & Parturition Flashcards

1
Q

how long is the mare estrous cycle

A

21-22d cycle

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2
Q

how many follicular waves are in the mare estrous cycle

A

1-4 waves per cycle

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3
Q

how long is the luteal phase in the mare

A

14d

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4
Q

how long is estrus

A

5-6d

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5
Q

when does ovulation occur

A

24-48hrs before the end of estrus

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6
Q

when does LH production peak and why

A

LH during estrus phase which is what supports the dominant follicle

LH peaks after ovulation –> different to the cow

Causes extremely rapid luteinization of the follicle wall (much quicker than cow)

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7
Q

what are the external characteristics of estrus

A

Favourable response to stallion

Clitoral ‘winking’ and frequent urination

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8
Q

what is seen on US during estrus

A

Large follicle(s) +/- soft

Follicle may be pointing near ovulation

No corpus luteum

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9
Q

what is the appearance of the cervix during estrus

A

Short, wide and relaxed

Pink and drooping

Lumen open

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10
Q

what are the external characteristics in diestrus

A

Switch tail, kick, squeal

Attempt to bite/avoid stallion

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11
Q

what are the ovarian characteristics during diestrus

A

Corpus lute

Follicles variable in size

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12
Q

what is the appearance of the cervix during diestrus

A

Long, narrow and firm

Pale and dry

Closed lumen

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13
Q

what is readiness for serving based on

A

External signs of estrus

Ultrasound and palpation

  • Uterus and cervix:
    • Closed and relaxed
    • Edematous —> cartwheel appearance
  • Follicle size and softness
    • Most 40-45mm in diameter before ovulation w
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14
Q

when is the timing of breeding

A

Max pregnancy rates when breed from 48hrs before to 6 hours after ovulation

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15
Q

how can ovulation be induced hormonally

A

Human chorionic gonadotrophin (hCG)

  • Hastens ovulation in cycling mares
  • Has luteinizing hormone (LH) activity
  • Follicle > 35mm ovulation within 48hrs of injection

Gonadotrophin releasing hormone (GnRH; deslorelin)

  • When follicles > 30mm induces ovulation within 48hrs of introduction of a subcutaneous implant
  • Stimulates release of FSH and LH from anterior pituitary gland
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16
Q

how is estrus synchronized in the mare

A

Progestogens/progesterone (regumate):

  • Administered for 14d
  • Estrus 4-7d after treatment
  • Ovulation occurs 7-12d after treatment

Prostaglandin F2a:

  • Mares with a mature CL — shortens luteal phase
  • Estrus 2-4d after injection
  • Ovulation occurs 7-12d after injection
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17
Q

what day does the embryo implant

A

day 16

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18
Q

what is the gestation length

A

330-345 days

Average 335 days

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19
Q

what day is fetal loss considered abortion

A

Abortion = before 300d

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20
Q

what day is the foal considered premature

A

300-320d

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21
Q

what type of placenta does the mare have

A

Diffuse, epitheliochorial

The entire surface of the chorioallantois is in contact with the endometrium, apart from a small area over the cervix (cervical star) where it will rupture at parturition

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22
Q

what is the appearance of the placenta that is in contact with the endometrium

A

Velvety, ‘villi’ surface of the chorioallantois that is in contact with the endometrium

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23
Q

how is the pregnancy maintained in the first 5 months

A

Maintained for the first 5 months of gestation via progesterone produced by the primary corpus luteum and supplementary corpora lutea

  • Initially pregnancy is maintained solely via progesterone released by primary CL associated with the original ovulation

From around day 40 equine chorionic gonadotrophin (eCG) released by the endometrial cups assist (along with pituitary gland hormones) in the formation of supplementary of corpora lutea

eCG may also help maintain the primary corpus luteum

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24
Q

what takes over maintenance of pregnancy after the first 5 months

A

There is then a transition period during which pregnancy maintenance by ovarian progesterone transfers to placental progestogens:

  • From around 1-2 months of pregnancy the fetoplacental unit produces progestogens (pregnanes) in increasing concentrations, peaking at 10 months of gestation
  • These concentrations are sufficient to maintain pregnancy from mid to late gestation
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25
Q

what are the nutritional requirements of the pregnant mare

A

Similar to maintenance for the first 8 months but there will be a need to gradual increase in nutrition in the last 3 months as 65% of fetal growth occurs in this period

Avoid overfeeding

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26
Q

what vaccines should the pregnant mare recieve

A

Tetanus vaccination (also influenza) 4-6 weeks before parturition

Boost immunity that will be transferred to the foal

If EHV-1 risk abortion, vaccination protocol for this disease

Given during the 5th, 7th and 9th month of pregnancy

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27
Q

what anthelmnitic control should the mare recieve

A

Normal parasite monitoring/control should continue, such as FWEC and anthelmintics used if required (generally not in last month of gestation)

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28
Q

which parasite can transfer to the foal via the milk

A

strongyloides westeri

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29
Q

why is deworming the mare not 100% protection to the foal

A

Deworming mares in late stages of pregnancy will not prevent infection, as foals are just as likely to acquire from the environment

Foals are asymptomatic and develop immunity by 5 months, patent infections are only seen in foals less than this age

Symptomatic foals display ill thrift and diarrhea — a differential within the incorrectly named ‘foal heat diarrhea’ syndrome

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30
Q

what are non infectious causes of aboriton

A

Twins

Premature placental separation

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31
Q

what are infectious causes of abortion

A

Viral:

  • Hematogenous spread ex. EHV-1

Bacterial:

  • Principally ascending infection ex. Streptococcus spp

Fungal:

  • Aspergillus
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32
Q

how can parturition be predicted using the serving date

A

Important to know the date to be able to estimate the possible window for parturition but it will be no guide as to when it will actually happen

Based on time from serving, often 7d before due date, and on some of the below signs it is usual to move the mare to a foaling box

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33
Q

when does the udder begin to enlarge prior to parturition

A

~4-6 weeks

Especially last 2 weeks

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34
Q

when does ‘waxing’ up occur

A

24-48hrs before parturition

Milk will leak in the final few hours

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35
Q

when does relaxation of vulva occur prior to parturition

A

few hours prior

36
Q

when does cervical softening occur prior to parturition

A

From minus 30d

Most marked during stage 1 parturition

37
Q

when do the sacroiliac ligaments relax prior to parturition

A

Gradually relax (tail head drop) over the last weeks of pregnancy, as will the cervix

38
Q

why is parturition prediction difficult

A

Prediction is obviously desirable and there are no reliable indicators of imminent parturition

Avoid consequences of dystocia

Provision of assistance

Most foalings after 6pm

Foaling often delayed with surrounding activity

Feeding, mucking out

39
Q

what mammary gland secretions can be monitored to predict parturition

A

Various stall side kits available

Electrolytes concentration change 24-48hrs prior

Ca2+, Na+, K+

Not absolute

40
Q

how is parturition initiated

A

Fetal maturation results in increased fetal pituitary secretion of ACTH and in turn this causes an increase in fetal adrenal cortex secretion of cortisol

41
Q

what role does fetal secretion of cortisol play in the induction of parturition

A

The conversion of progestogens to cortisol by the fetus causes maternal progestagens levels to plummet

This results in estrogen becoming dominant in the periparturient mare

42
Q

the switch from progesterone to estrogen production by the placenta results in what events

A

Estrogens promote the synthesis of prostaglandins and myometrial gap junctions

Estrogen dominance causes cervical production of prostaglandins that promote cervical relaxation

43
Q

what are the roles of prostaglandin in parturition

A

The myometrium becomes increasingly responsive to oxytocin and prostaglandins overcoming the inhibitory effects of relaxin

Myometrial contractions push the chorioallantoic sac against the soft cervix and stage 1 of parturition commences

Stage II parturition is driven by rising oxytocin and prostaglandin concentrations

44
Q

what is the role of relaxin

A

An increase in relaxin production by the placenta may keep the uterus quiescent until just before parturition and is believed to be involved in softening ligaments of pelvis

45
Q

describe the hormones of parturition

A

etal maturation results in increased fetal pituitary secretion of ACTH and in turn this causes an increase in fetal adrenal cortex secretion of cortisol

This significant increase in fetal cortisol, in the last two days of gestation culminates in parturition:

  • The conversion of progestogens to cortisol by the fetus causes maternal progestagens levels to plummet
  • This results in estrogen becoming dominant in the periparturient mare
  • Estrogens promote the synthesis of prostaglandins and myometrial gap junctions
  • An increase in relaxin production by the placenta may keep the uterus quiescent until just before parturition and is believed to be involved in softening ligaments of pelvis
  • Estrogen dominance causes cervical production of prostaglandins that promote cervical relaxation
  • The myometrium becomes increasingly responsive to oxytocin and prostaglandins overcoming the inhibitory effects of relaxin
  • Myometrial contractions push the chorioallantoic sac against the soft cervix and stage 1 of parturition commences
  • Stage II parturition is driven by rising oxytocin and prostaglandin concentrations
  • Prolactin is also increasing around this time resulting in mammary development and milk production
46
Q

what are the last steps of fetal maturation and why are they essential to life

A

The rise in fetal cortisol is vital for the final maturation of the foal

  • If this does not occur then foals generally fail to thrive and often die, this may occur in a premature foal

Cortisol contributes to the maturation of the lungs just prior to parturition

  • This maturation plus the presence of the surfactant, are essential for effective lung inflation in the adaptive period
47
Q

what are the indications of parturition to be induced

A

Hydrops

Prepubic tendon rupture

Ventral herniation

48
Q

what are the complications of parturition induction

A

Dystocia

Premature placental separation

Fetal hypoxia and dysmaturity

49
Q

what is the major hurdle to induction of parturition

A

Fetus undergoes final maturation in the last two days of gestation

Induction should happen when this has occurred — but we know that this is very hard to judge and is guided by vague factors like time since serving, mammary development, milk production/changes and eventually cervical softening

50
Q

how is induction don e

A

Low dose oxytocin regimen:

Prostaglandin (PGE2) is administered topically into the cervix in an attempt to accelerate softening

51
Q

what are the events of stage 1 of parturition

A

Preparation for fetal expulsion

52
Q

what are the signs of stage 1 of parturition

A

Sweating, restlessness, mild colic for 1-4 hours, up to 24hrs

53
Q

how does the fetus reposition in stage 1 of parturition

A

Dorsopubic to dorsosacral

Head and forelimbs form ‘wedge’ at cervix

54
Q

what does stage 1 of parturition end with

A

Stage 1 ends with chorioallantoic rupture — ‘waters’ break

55
Q

what are the events of stage 2 of parturition

A

Expulsion of foal via abdominal and uterine contractions

56
Q

how long should stage 2 take

A

Should take less than 20 minutes

Any longer than that — assistance

57
Q

how does stage 2 of parturition commence

A

Rupture of chorioallantois

  • Loss of allantoic fluid
  • Exposure of amniotic membrane
58
Q

what does stage 2 of parutrition end with

A

Ends with expulsion of foal

59
Q

how long should the umbilical cord be left intact after parturition

A

Ideally umbilical cord should remain intact after birth to allow return of foal’s blood from placental to the foal

Usually broken at stricture 2-3cm from the foal’s abdomen when mare gets up

60
Q

what are the events of stage 3 parturition

A

Expulsion of fetal membranes via uterine contractions within 3 hours

61
Q

what are the signs of stage 3

A

Mare will show signs of mild colic during this process

62
Q

when is the fetal membrane considered retained

A

>3 hours

63
Q

how can RFM be removed

A

Aid expulsion by oxytocin therapy/fluid distension of chorioallantois, not by manual traction

64
Q

how should you examine the placenta

A

Body and both horns — nothing missing (lay out in F)

Normal appearance

65
Q

what can RFM lead to

A

One small piece is as bad as whole placenta

Metritis can lead to septicemia/endotoxemia, laminitis, death

66
Q

what is a red bag delivery

A

Chorion separates from endometrium

Chorioallantois passed without rupturing

Palpate foal inside (if could be a bladder eversion — especially if dystocia) and then you should immediately rupture the chorioallantois

67
Q

what are the causes of dystocia

A

Fetal malpresentation

Fetal malposition

Fetal malposture — most common

Fetomaternal disproportion (no where near same problem as in certain cattle/sheep breeds)

Congenital abnormalities

Twinning

Uterine torsion/inertia

Hydrops

68
Q

what is the most common cause of dystocia

A

malposture of foal

69
Q

what history questions should you ask when approaching a dystocia

A

When due to foal, previous foaling, problems during pregnancy, general health, when parturition started, any attempt to intervene

70
Q

how should you assess a mare with dystocia

A

Want standing for initial exam

Try to maintain sterile hygiene by cleaning the perineum and tail bandage

Clean arms/hands or rectal gloves with surgical gloves over top

Determine presentation, position and posture as well as mare status and if foal is alive

71
Q

what is the presentation of a foal and what is the correct presentatino

A

Longitudinal or transverse?

Relationship of spinal axis of fetus to dams

Longitudinal cranial — head entering canal

Longitudinal cauda — tail in longitudinal presentation

Transverse — ventral or dorsal

72
Q

what does the position of the foal mean and what is normal

A

Relationship of foal’s dorm to mare’s pelvic quadrants

Longitudinal presentation

  • Sacrum, right ilium, left ilium or pubis
  • Normal is dorsal sacral

Transverse presentation

  • Relationship of head to the quadrants
73
Q

what is the posture of the foal

A

Deviation of head/neck very common (cranial presentation)

Relationship of fetal extremities to fetal body

  • Head, legs
  • Flexed, extended
74
Q

how can you determine if the fetus is still alive in dystocia

A

Try to stimulate response from foal

  • Pinch coronary band, pressure on eyelid
  • Can also feel heartbeat (thorax) or even palpate umbilical pulse (umbilicus)

Check mare for trauma (especially canal) — previous failed attempts to pass foal

75
Q

how can you determine mare status in dystocia

A

Check mare for trauma (especially canal) — previous failed attempts to pass foal

76
Q

how can you help in assisted vaginal delivery

A

Mutation:

  • Manipulation of fetus to ensure successful delivery
  • Often repulsion
  • Limited time frame for attempt — 10-15mins

Traction:

  • No mechanical assistance
77
Q

if assisted vaginal delivery is not possible what are the options

A

Foal dead - fetotomy

Mutation/traction under GA

C-section

78
Q

if referral is not an option for c section what are the options

A

Sacrifice foal for life of mare (fetotomy), usually by the time you are at this stage the foal is dead

79
Q

how is fetal manipulation usually done

A

repelling the fetus

A large volume of warm water and lubricant may help Several litres via sterile stomach tube

Gravity or pump

80
Q

how is head flexion done

A

Place rope around ears and through mouth

Before repel

Grasp jaw/muzzle/ears

81
Q

how is limb flexion corrected

A

Limb flexion:

Repel carpus or hock while traction put on foot (cup it)

82
Q

how can an epidural help

A

But takes time to administer and does not stop all straining

Not always the answer

83
Q

how can IV clenbuterol help

A

IV clenbuterol at 0.17-0.35mg/465kg

Uterine relaxation

Not thought to increase risk prolapse or retained placenta

But some clamp vulva post foaling if used

84
Q

if sedation is needed for the mare during dystocia what should you do

A

Xylazine (only if only option detomidine)

Xylazine plus butorphanol

85
Q

how can you reduce the straining in dystocia

A

Keep mare walking

Stop glottis closing so mare can’t use diaphragm to assisted abdominal straining NG tube placed in trachea

Pull tongue out

86
Q

if there is a prolonged dystocia and the foal’s mouth/nose is accessible what should you do

A

Placenta likely compromised

Therefore oxygen (if available) or air via ambu bag

  • Via intranasal tube
  • Nasotracheal intubation
  • Face mask
  • 10-20 breaths per minute
87
Q

what does a post partum mare/foal check involve

A

History of pregnancy and parturition:

  • Was it witnessed? When did it happen?

Observation of mare:

  • Demeanour dull or could be fractious
  • Interest in foal?

Routine clinical exam

  • Mammary glands
  • Milk? Engorged? (might suggest foal not suckling)

Examine for trauma:

  • Perineum and vulva — how much further you investigate might depend on the history of parturition (was it witnessed?)

Full exploration of the expelled placenta:

  • Is it all there?
  • Is it healthy?

Monitor for signs of colic

Module 22: Reproduction & Fertility (27 decks)

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