Equine Stud Medicine

Question 1

Owner Understanding Implications:

Answer 1

Costs - transport, vet, livery
Facilities - foaling box, paddocks, expertise
Time - care & management

Question 2

Oestrus Cycle

Answer 2

Seasonally polyoestrus
Long day breeders - march/april

Spring Transition:
* Irregular oestrous behaviour
* Transitional ovary (multiple anovulatory follicles)

Normal Oestrus Cycle:
* Mean duration: 21 days
* Oestrous: 3-7 days (variable)
* Diestrus: 14-15 days

Ovulation:
* ~ 24 h before end of oestrous

Question 3

Mare’s Cycle - Oestrus:

Answer 3

• Mare is sexually receptive
• High Oestrogen and LH and low progesterone
• Cervix pink, moist, relaxed, open and oedematous
• Uterus oedematous & flaccid

Question 4

Mare’s Cycle - Dioestrus:

Answer 4

• Mare rejects the stallion
• High circulating progesterone (rises sharply after
  ovulation)
• CL present
• Follicular growth occurs
• Cervix pale, firm, dry and closed
• Uterine tone increases
• PGF2a released from uterus on day 14 or 15 causes luteolysis & return to oestrus

Question 5

Pre-breeding Exam - Mare

Answer 5

• Signalment
• History
• General health and fitness
• Reproductive exam:
  1. Genitalia
  2. Reproductive tract
  3. Mammary glands
• Required tests and paperwork → Passport/CEM
• Check stud requirements

Question 6

Signalment - Age

Answer 6

• Puberty: 1-2 years
• Some breeders like to cover at 2 years (breed dependent)
  → Must be well grown and adequately fed for growth and reproduction
• First covering at 5 to 6 years is optimal
• Conception rate decreases after 6 years
• Conception & foaling rates significantly decreased for maiden mares >12 yo → Common for performance mares

Question 7

Signalment - Breed:

Answer 7

• Pony breeds are intensely seasonal
  → But breed more successfully at older ages
• Thoroughbreds require advancement of breeding season

Question 8

External Genitalia:

Answer 8

Perineal and pelvic confirmation
* Integrity of the 3 caudal reproductive tract seals
→ Vulva, vestibule, cervix
→ Essential to prevent airborne or faecal contamination of the uterus
* Vulval conformation: 1st line of defence
→ Vulval lips meet on midline → Vulval seal
→ 80% of vulval opening below pelvic brim
→ Vulva < 10° off vertical
Pneumovaginum → faecal contamination
- can fix with sutures

Question 9

Vaginal Examination:

Answer 9

Assess vestibular seal (2nd line of defence) and cervix (3rd line of defence)
* Aseptic procedure
‒ Mare back and washed and tail tied up.
‒ Sterile gloves
a) Manual (sterile): Feel - Integrity of vaginal wall and cervix?
b) Visual (sterile) speculum exam: Inspection of cranial vagina and cervix.
* Urine pooling
* Varicose veins
* Competence of cervix

Question 10

Cervix:

Answer 10

1. Dioestrus cervix - pale, firm, dry, closed
2. Onset of oestrus -> pink, swollen, begin to open, folds less
3. Towards end of oestrus -> pink, moist, swollen, relaxed, folds hang down, vascular appearance
4. Pregnant cervix -> very hard, tightly closed, covered in pasty mucus

Question 11

Rectal Exam:

Answer 11

• Rectal palpation
  → Uterus and Ovaries
• Systematic approach
  → Defines individual mare anatomy prior to ultrasonography
• Generates info which augments subsequent ultrasonographic findings
  → Ovarian size and shape,
  → Follicle size, consistency, location
  → Uterine tone, consistency, pregnancy
• Rectal tears potentially life threatening:
  → Never ignore blood on sleeve!

Question 12

Transrectal Ultrasound

Answer 12

Uterine fluid
Uterine oedema
Uterine cysts
Uterine horn & body
Ovaries

Question 13

Uterine Oedema Grading:

Answer 13

Grade 0 - no oedema
Grade 1 - small amount of oedema
Grade 2 - moderate amount of oedema
Grade 3 - large amount of oedema target

Question 14

Uterine Fluid:

Answer 14

• Fluid build-up in the uterus can prevent establishment and maintenance of pregnancy
• Fluid seen prior to breeding:
  → Treat if >1cm.
  → Treat & Investigate if >2cm?
• Often seen post breeding
  → natural response to foreign material. Most mares clear this in 24-48 hours
• Older mares/multiparous/poor conformation → delayed uterine clearance → low grade endometritis

Question 15

Prevention of Venereal Disease

Answer 15

Routine:
- Bloods - EVA, EIA
- Clitoral swabs - CEM
- Endometrial swab

Question 16

Diseases Tested For:

Answer 16

Equine Viral Arteritis (EVA) – Notifiable
→ Blood test – ELISA
→ Semen accompanied by a certificate confirming disease free status

Equine Infectious Anaemia (EIA) – Notifiable
→ Blood test – ELISA or Coggins test

Contagious Equine Metritis (CEM) – Notifiable
→ Taylorella equigenitalis
→ Clitoral swab, endometrial swab

Klebsiella pneumoniae (clitoral swab, endometrial swab)
Pseudomonas aeruginosa (clitoral swab, endometrial swab)

Question 17

Clitoral Swabs:

Answer 17

• Required for all breeding (AI and natural service)
• After January 1st
• Clitoral sinus and fossa
• Do NOT clean site before swabbing
• Klebsiella pneumoniae
• Pseudomonas aeruginosa
• Taylorella equigenitalis – NOTIFIABLE CEM

Amies Charcoal transport medium
→ Culture +/- PCR
→ Aerobic and microaerophilic culture

Question 18

Endometrial Swabs:

Answer 18

• Not done in every case (cf clitoral swabs)
• Required for natural service
• Collected during estrus
• Aseptic procedure
• Double guarded swab
• Smear for cytology on glass slide
• Place swab into appropriate transport culture media → Aerobic culture +/- microaerophilic culture

Question 19

Natural Service

Answer 19

Pasture Mating:
Adv - labour efficient, cheapest
Disadv - venereal infection, injury

Hand Mating:
Adv - less injury, conserves stallion
Disadv - time & labour intensive, increased cost

Question 20

Artificial Insemination:

Answer 20

• Increased choice of stallions
• Access to stallions that are geographically inaccessible (or dead!)
• Decreased risk to mare (of venereal disease etc) compared with natural insemination
• Eliminates risk to stallion
• Mares with young foals do not need to be transported
• Decreased travel cost and inconvenience but increased equipment/facilities/labour costs

Stallion Considerations:
Where is stallion based and what format is semen available?
‒ Fresh (stallion needs to be onsite)
‒ Chilled (Stallion needs to be on same continent)
‒ Frozen (Worldwide – providing semen is in the UK prior to breeding)
How much notice is needed for (chilled) semen?
‒ (Normally approx. 2 days)

Question 21

Breeding Protocol

Answer 21

Initial Exam:
- Mare evaluation
- Stage oestrus cycle
- Treat to advance ovulation

Subsequent exams:
- Monitor changes
- Predict/ induce ovulation

Inseminate/ mate
Post breeding exam

Question 22

Semen Evaluation

Answer 22

• Motility
• Morphology
• Volume and Concentration
• Fresh – Immediate use → 500 x 106 PM sperm
• Chilled – Delayed use (24h) → 500 x 106 PM sperm
• Frozen – Delayed use (whenever) → 300 x 106 PM sperm

Question 23

Semen:

Answer 23

Semen survival in mare:
→ Fresh – approx. 72 hours
→ Chilled – approx. 36 hours
→ Frozen – approx. 12 hours

Question 24

Prostaglandins:

Answer 24

Corpus luteum present, No oedema, Cervix tight

Question 25

Induce Ovulation

Answer 25

1. Simulate ‘LH surge’ * Human chorionic gonadatrophin (hCG) → Follicle 3.5cm plus uterine oedema 3 → ‘Chorulon’, 1500 to 3000iu IV → >80% mares ovulate within 48h (mean 36h) 2. Simulate ‘GnRH surge’ to induce endogenous LH secretion * Deslorelin → Follicle >3cm, some uterine oedema → ‘Ovuplant’, single s/c implant in ‘bleb’ LA in vulval lip or 1-2mg IM → Remove implant after mare has ovulated (post insemination) → 90% mares ovulate within 36-42h

Question 26

Semen Quality:

Answer 26

* Warmed microscope stage essential * Prepare microscope and slides BEFORE opening semen container * Mix semen gently and add a 20μl drop to a warmed (37oC) slide and cover * Place on warm stage and assess percentage of sperm which are PROGRESSIVELY MOTILE after 1 minute. * Assess morphology Check before insemination - fresh and chilled Check after insemination - frozen

Question 27

Insemination

Answer 27

* Mare restrained in stocks * Mare prepared: → Tail wrapped in sleeve or tail bandage and held to the side → The perineum is washed with water ONLY and then dried * If chilled semen: usually arrives in pre-filled syringe, does not require warming (cf frozen semen) * Semen loaded into insemination syringe and catheter * Sterile rectal sleeve sterile KY jelly utilised * Deposit semen in body of uterus

Question 28

Frozen:

Answer 28

* Ideally inseminated at the same time as follicle is ovulated * Oocyte only lasts 6 hours post ovulation therefore must keep checking the growth of the follicle every 6 hours * At ovulation, semen removed from liquid nitrogen and placed in water bath at 37°C for 30 seconds * Dry with paper towel, collect into catheter, place into uterus and inseminate * Water is highly spermicidal → Vulva → Water bath

Question 29

Frozen Semen Insemination

Answer 29

More precise insemination time * 12h before to 6h after ovulation Option 1 - Monitor Frequently * Induction to ovulation * Time consuming * Semen conservative * Better conception rates Option 2 - 2x fixed time inseminations (42-48hrs after hCG) (Mare must have appropriately sized follicle and maximal uterine oedema) * Ensures fertile sperm are present within 12h before to 6h after ovulation * Time conservative * Semen consuming * Similar conception rates possible

Question 30

Post Breeding US Exam:

Answer 30

* Usually 24h post-service → Confirm ovulation (CH) → Detect and treat abnormal fluid accumulations in uterus Fluid accumulation (poor uterine clearance = common) Low volume (< 1cm): o Oxytocin: 20iu IM & IV o Can be initiated 4h post-breeding and continue every 6h until clear High volume o Uterine lavage (up to 3L in total) o Oxytocin: 20iu IM & IV o Antibiosis (intra-uterine) if suspicious of infection or following swab results Persistent mating-induced Endometritis (PMIE) o Prolonged inflammation (>48h) of endometrium caused by sperm o 10-15% of mares affected * If fluid clear (hypoechoic) on US → likely sterile * If fluid cloudy (hyperechoic flecks) → suggests infection * Embryo arrives in uterus day 5 after ovulation – all ‘clean-up’ work (lavage, etc) must be done before this.

Question 31

Pregnancy Diagnosis

Answer 31

* Day 14 post ovulation → Pregnancy diagnosis: 14-18mm → If there is only one pregnancy, check for a second CL * Day 16 → Management of twin pregnancies → Much easier before implantation on day 17 * Day 28 after ovulation → Heartbeat scan

Question 32

Twin Pregnancies

Answer 32

* Major cause of abortion if allowed to carry * Abort due to lack of placental area to support 2 fetuses * TBs: 20-30% multiple ovulation rate Treatment: * Manual reduction prior to implantation * If different sizes, the smaller vesicle is reduced * Separate embryos * Administer flunixin meglumine and altrenogest? * Recheck the mare the next day

Question 33

Embryo

Answer 33

* Collection of fertilized oocyte (embryo) from donor mare * Transferring it to synchronized reproductive tract of recipient mare * Step 1: Synchronize ovulation between donor and recipient mares * Step 2: Inseminate donor mare * Step 3: Donor mares uterus flushed at 7-8 days post ovulation to retrieve the embryo * Step 4: Retrieved embryo is transferred into the uterus of a recipient mare * Embryo recovery and transfer rate – 50-70% * Pregnancy rate – 25-50%