Equine Flashcards
Where is semen deposited?
The uterus
What are the 3 barriers to infection?
Vulva
Cervix
Vestibulo-vaginal sphincter
What surrounds and suspends the ovary?
The mesovarium
Are the ovaries fixed or moveable?
Fixed
How do the cortex and medulla differ in the horse compared to other species?
The cortex is on the inside - germinal epithelium
The medulla is on the outside
Where does ovulation occur through?
The ovulation fossa
When does the CL form?
Once ovulation occurs
Where is the fornix located?
around the entire cervix
What percentage of the vulva should be below the pelvic floor?
70%
How does luteolysis differ compared with a cow?
It is exerted via a systemic pathway rather than local venoarterial exchange in cattle
Significance -> need smaller doses of prostaglandin for luteolysis
How is a mares cycle described?
Seasonally polyoestrus - long day breeders
How long is the period after parturition and before foal heat?
9 days average
How long is a mare’s cycle?
21 days
How long is oestrus?
4-8 days
When does a mare ovulate?
Anytime in her 4-8 day long oestrus
When is a CL developed?
Early dioestrus -> not responsive to PGF2a
5 days following ovulation responsive
What happens to the CL in late diooestrus?
It becomes responsive to PGF2a (13 days)
What happens in the luteal phase and how long does it last?
Dioestrus -> time after ovulation
Progesterone increases due to CL presence (ready to accept potential embryo)
18 days long
What happens in the follicular phase?
Oestrus -> 4-8 days long
Mare TUW -> Tail up, urinating and winking
What is the transitional phase?
40-60 days long between anoestrus and normal cycling oestrus
What hormone dominates the autumn transition?
Oestrogen -> follicles, some uterine oedema, but no CL and dont go on to ovulate
What is a vernal transition?
AKA spring transition
First heat of the cycle -> no ovulation, oestrogen dominance
Pineal gland picks up light cues
How long is the vernal transition?
60-90 days
Dominated by light
How can we shorten the transitional period?
Drugs -> GnRH analogues, dopamine agonistss, oestrogens or progestagens
Light -> for 60 days from July-September
How does progestagen shorten the transition?
It doesn’t -> it synchs ovulation
How does dopamine antagonists shorten the transition?
Increases prolactin -> stimulates follicle growth
Do hCG or deslorelin induce ovulation in transition follicles?
No - they do not have LH receptors
In what animals are silent heats most common?
Wet mares - foal proud
How do we manage multiple ovulations?
Breed to the second follicle
Check for twins at 14-16 days after breeding - get rid of the smaller one
What is a dioestrus ovulation?
Ovulation during luteal phase with high progesterone interfering with PGF2a action, resulting in long luteal phase
What do early or late dioestrus ovuations result in?
early -> pregnancy
Late -> prolonged luteal phase
How to persistent CLs occur and how long can they last?
Spontaneously (failure of Pg release), early pregnant loss, dioestrus ovulation
Last 35-90 days
How do we diagnose a persistent CL?
Increased uterine tone, ultrasound
How do we treat a persistent CL?
PGF2a -> repeat in 5 days if no response to first dose
What are 2 causes of constant oestrus behaviour?
True nymphomaniacs -> alternate oestrogen source (tumour, adrenal gland)
Granulosa theca cell tumour -> depends on predominant cell type (testosterone, oestrogen, inhibin) - will produce normal progesterone in early stages - elevated AMH has tumour
How is prostaglandin used to manipulate the cycle - when are injections given and when is the CL responsive?
Injections 14-16 days apart
CL responsive from 5-6 days following ovulation (day 13)
Shortens luteal phase to initiate new cycle
How are progestagens used to synchronise mares - what are the 3 methods?
Often used with oestrogen
Regumate -> Oral administration for 14 days and oestrus 5 days after withdrawal
Natural -> in oil - not practical
Cue Mare - CIDR can form vaginitis
How are progestagens used to synchronise mares?
Regumate -> Oral administration for 14 days and oestrus 5 days after withdrawal
Natural -> in oil - not practical
Cue Mare - CIDR can form vaginitis
How is oestrogen used to synchronise oestrus - Dose and time period
150mg P4 and 10mg E2 for 10 days
Ciderol + CIDR works well
Tighter synchrony with both
Follicle is 35mm -> induce ovulation
What 3 things can be used to induce ovulation?
hCG
Deslorelin acetate - injectable
Deslorelin acetate - ovuplant
How does hCG induce ovulation, what follicle size can it be used on and when will ovulation occur?
Use on >35mm follicle for ovulation in 36 +/- 6 hours
LH like substance - increases follicle development
How does injectable deslorelin induce ovulation and what follicle size does it work on? when will ovulation occur?
Use on >30mm follicle for ovulation in 40 +/- 3 hours
GnRH agonist -> stimulates pituitary release of LH
Can the deslorelin implant (Ovuplant) be used to induce ovulation in mares?
No - discontinued
List 4 methods to prevent ovulation/oestrus
- Progesterone - no oestrus behaviour
- GnRH vaccine
- Oxytocin
- Ovarioectomy - stops ovulation, not oestrus behaviour
How does the GnRH vaccine prevent ovulation?
Reduces LH and FSH
for 3-6 months
Discontinued -> infertility in some cases
Does not stop adrenal oestrogen
How does a GnRH analogue prevent ovulation?
Overload of GnRH -> downregulates HPG axis to switch off GnRH production
Doesnt work in all horses and will cycle after 3-4 months
Does not stop adrenal oestrogen production
How does oxytocin stop ovulation and at what dose for how long? What are 2 methods?
60IU oxytoxin for 7 days starting 7 days post ovulation
Prolonges CL life - longer luteal phase (fake maternal recognition of pregnancy)
Marble -> high failure rate 70%
U-POD -> magnetic and better retention
How does a GnRH agonist stop ovulation?
Discontinued - Ovuplants
Prolonged interovulatory interval due to maintaining CL and producing small GnRH
Desensitises HPG axis
List 6 causes of abnormal cycles
- True non-seasonal polyoestrus (20% cycle all year)
- Multiple ovulations during oestrus (delay/lengthen luteal phase)
- Lactational anoestrus (does not happen in horses)
- Constant oestrus (tumours producing steroids)
- Genetic (may not have 2 X)
- Silent heat
Advantages of paddock breeding
Teach stallions normal sexual behaviour
low labour
good selection for repro performance
Experienced stallions- 70-80% rates
Disadvantages of paddock breeding
Injury to stallion
Reduced efficiency of stallion
Reduced pregnancy rates
Risk of twins
Advantages of AI
Genetic progress - exploit superior male Dont need to own stallion International access Safety for females Minimal animal transport - biosecurity
Disadvantages of AI
Labour intensive $$
need special facilities and experienced technicians
Semen costly
Reliance on couriers
6 neccessities for live cover
- Pre-breeding swab for STI
- PPE
- Cleanliness - wash mare and stallion
- Ovulatory drugs to minimise serves
- Teasing
- Ultrasound exam - identify ideal breeding time and pregnancy/twins at 15 days
What is equine coital exanthema?
Equine herpes virus 3 veneral pathogen
affects males and females signs 4-7d after contact
Pustules and ulcers
How is equine coital exanthema treated?
sexual rest for 3 weeks and topical antimicrobials
Name 3 bacterial venereal pathogens
- Contagious equine metritis (taylorella equigenitalis) - not in Aus
- Klebsiella spp.
- Pseudomonas - water based
Name 3 viral venereal pathogens
- EHV-3
- Equine viral arteritis
- Equine infectious anaemia
Name 1 protozoan venereal pathogen
Trypanosoma equiperdum
How long after collection should chilled, extended semen be inseminated?
24-48 hours
How cold should frozen sperm be stored at?
-196 degrees in liquid N
After 3-4 hours at 37 degrees, how many sperm will be alive?
None
Why do we use semen extender?
To extend motility and viability and allow antibacterial treatment of sperm
Increased lipid content -> stabilise sperm membranes from cold shock
Affects of cold shock
Damage to sperm membrane and acrosome
Loss of motility and decreased metabolism
Name two protective agents for sperm
Egg yolk - low density lipoproteins insulate sperm
Bovine serum albumin - protect against oxidative stress
Disadvantages of chilling semen
Cost - transport, risk of late delivery
Not all males suitable - sperm quality
Damage during preparation
Needs to be used in 48 hours
3 Steps of collecting semen
- Collect - dummy, AV
- Process and analyse -> extend in dilutent, certifuge and resuspend in media
- Pack, chill + send -> 50ml falcon tubes or whirl pack bags
Labels, lids + semen assessment
Disadvantages of frozen semen and what is the pregnancy rate?
Pregnancy rate 40% per cycle
Success depends on: Post thaw fertility of stallion, suitable mare, bred within 6-12 hours of ovulation
Ideal frozen AI mare
<12 years old, maiden and no history of breeding induced endometritis
or older mares that have recently foaled (not on foal heat)
How do we thaw frozen semen?
0.5ml straw - 30 degrees for 30 seconds
Timing of insemination
Ideally 3 hours of ovulation -> sperm do capacitation in freezing process and die 12 hours after this
oocyte viable for 6-12 hours
List 5 methods of insemination
- Uterine body insemination
- Deep uterine horn insemination
- Surgical oviductal insemination
- Laparotomy
- GIFT
How is deep uterine horn insemination performed?
Atraumatic flexible catheters 0.5-1.5ml
100 million sperm
Eliminates uterine transport - rectally guided to anterior uterine horn - ipsilateral to impending ovulation
Routine for frozen sperm
How is hysteroscopy performed?
$$ equiptment and labour - need 3 people
Sedate + ensure it goes up one horn
Use with low dose insemination
Young healthy mares and ovulation induction
What is involved in surgical insemination and what is it called?
Gametic intrafallopian transfer (GIFT)
Egg and sperm into uterine tube
Capacitation occurs in oviduct
What are 5 things we need to know about a mare’s history before we breed?
- Identification
- Breeding status
- Cycle histoy
- Confirmation
- Disease status
What are 3 things we look for on ultrasonography and rectal palpation?
- Ovarian activity - CL, dominant follicles
- Uterine tone and oedema
- Abnormalities
What will the ovary demonstrate in anoestrus?
No follicular activity (<10mm)
Dense, small ovarian tissue
What will the uterus show in anoestrus?
Faccid
Thin walled, quiescent
What will the cervix show in anoestrus?
Pale, dry and high
Partially open but not relaxed
What will oestrus cause the cervix and uterus to show?
Cervix - soft
Uterus - oedema
What happens to GnRH during gestation?
It is inhibited by progesterone
What are 3 methods to complete an intrauterine culture?
- Endometrial culture swab
- Low volume uterine lavage
- Uterine biopsy
What are 3 methods to complete cytology?
- Swab
- Cytology brush
- Uterine lavage
What are 3 causes of infectious and 3 causes of non-infectious endometritis?
Infectious -> bacteria, yeast, fungus
Non-infectious -> air, urine, post breeding
What are 2 bacterial agents that can cause endometritis?
Streptococcus
E. Coli
What months is the autumnal transition?
May-June
What months is winter anoestrus?
July-August
What months is spring transition?
September-October
If a mare has a 40mm follicle in September and oedematous uterus, what should we do?
Breed her (live cover) and induce with chorulon
When should we induce a mare that is to be bred with cooled semen?
24 hours prior
When should we induce a mare that is to be bred with frozen semen?
40 hours prior
What do we do if post breeding she has ovulated, there is fluid in the uterus and a CL present?
Flush the uterus with a sterile saline lavage - can do this up to 72 hours post-ovulation
Give Oxytocin in small frequent doses 4-6 horus post breeding
When can we use rectal palpation for pregnancy diagnosis?
Day 24 to term
When can transrectal ultrasonography be used for PD?
Day 9 onwards
What structure is unique to horses in early embryo growth?
Acellular glycoprotein capsule
When is the acellular glyoprotein capsule first detected and when does it persist until?
6-7d first seen
23d leaves
Does the horse go through elongation?
No - due to the presence of the capsule
How does maternal recognition of pregnancy occur?
Presence of the conceptus prevents PGF2a
How many scans are done in a practical pregnancy diagnosis?
4
When is the first scan done?
14-16 days for twin check
When is the second scan done?
21-30d to check for heartbeat
When is the third scan done?
40-45d
Post-attachment and organogenesis
When is the 4th scan done and what are we checking?
60-70d
Fetal sexing
When are endometrial cups present and what do they produce?
36-120 days
Equine chorionic gonadotrophin -> LH effect to lyse secondary follicles
What hormones maintain pregnancy and where are they produced?
Primary and accessory CL -> P4
Placental and foetal gonads - oestrogen + progestagens
What are 6 causes of infectious abortion in the mare?
- Equine herpes virus
- Bacterial abortion
- Equine amnioitis and fetal loss syndrome (EAFL)
- Chlamidya psittasci
- EIA
- Equine viral artiritis
When does EHV cause abortion and where is the most viral load found?
Last 4 months
Aborted fetus and fetal membranes
What do bacterial abortions cause and what are 3 agents?
Staph
Strep
E.Coli
Ascending Placentitis
What type of abortions do EAFL cause and what are clinical signs?
Mid-late term catepillar associated abortions - mares grazing affected areas
Amnionitis and funisitis
When does chlamidya psittasci cause abortion and is it zoonotic?
Yes
Late term
When does EIA cause abortion?
At the time of infection
When does equine viral artiritis cause abortion?
1-4 weeks after respiratory infection
What are 6 causes of non-infectious abortions?
- Undiagnosed twins
- Fescue toxicity
- Umbilical cord torsion
- Placental insufficiency (endometrial cysts)
- Nutrition
- Trauma
What are the 3 types of placentitis?
Ascending
Haematogenous
Unknown - Nocardiform
How does ascending placentitis happen?
Bacteria breach 3 barriers to uterus
How does haematogenous placentitis happen?
Through systemic illness or bacteraemia - Lepto, Klebsiella, Pseudomonas, staph, strep or salmonella
What defines placentitis?
Inflammation +/- infection of the placenta causing disruption of blood supply
What are 3 signs of placentitis?
Vaginal discharge
Premature mammary development
Increased thickness of the placenta on ultrasound
How do we treat placentitis?
Antimicrobials, anti-inflammatories and progestagens
When can a eCG assay be done?
Day 36-90
How do we prevent equine herpes virus?
Duvaxyn vaccine
Vaccinate at 5,7,9 months gestation
Not highly effective so use in valuable mares
