Mare Breeding Exam

Question 1

what does the mare breeding soundness involve

Answer 1

Clinical protocol for investigation of a mare prior to breeding

Full history

Physical exam

Gynaecological exam

Internal

External

Question 2

what history of the mare should be gathered

Answer 2

Age/breed/purpose

General health status

Last parturition:

• Date, difficulties

Number of previous foals (live and dead)

Abortions/problem pregnancies

Estrous cycle

• Length
• Duration

Previous gynaecological exams/treatment

Number of previous matings/mating interval

Lactation problems

Struggling to produce milk?

• Enough to feed previous foals

Question 3

what other things should you consider in the history of a mare

Answer 3

Temperament:

• Stress and poor reproductive performance

Age: >12 years

• Increased infections/adhesions
• Increased aggression to stallion
• Positive correlation age: poor fertilization rates, endometriosis
• Multiparous = additional problems

Question 4

what is the ideal body condition of a mare

Answer 4

2.5-3

Question 5

what does the gynaecological exam entail

Answer 5

Perineum, vulval seal

Clitoral swab

Examine vagina and cervix

Endometrial bacteriology

Endometrial cytology

Endometrial biopsy

Rectal examination

Ultrasound examination

Endoscopic examination

Blood sample:

• Hormone/chromosome analysis

Question 6

what should the normal vulva conformation be

Answer 6

The vulval forms the external opening of the reproductive tract

First effective barrier to protect the uterus from ascending infection

Vulval lips aligned vertically

Meet in mid-line to form an effective seal

Question 7

what is caslick vulvoplasty procedure

Answer 7

Local anesthetic

Trim a thin mucosal strip from mucocutaneous junction

Simple interrupted or simple continuous suture

Question 8

what is the length of estrus

Answer 8

4-7d

Question 9

what is the length of diestrus

Answer 9

14-16d

Question 10

how long does estrus behaviour persist after ovulation

Answer 10

24-48hrs

Question 11

how can we control the photoperiod

Answer 11

16 hours of light

8 hours darkness

Bright white light (200W)

Light stimulus via optic nerve to pineal gland which suppresses melatonin release in turn affecting GnRH and LH/FSH

Must be started a minimum of 8-10 weeks before mare required to be covered

At end of lighting regime may treat with synthetic progestagen for 10-15d

• Also controls number of mare ovulating
• Regumate

Human chorionic gonadotrophin or GnRH can be used to ensure mares ovulate at predictable time

• 24-48hrs after administration

Question 12

what follicle size ovulates and how much growth in a day

Answer 12

Large pre-ovulator follicle

Mares less likely to ovulate a follicle less than 35mm

Grow at a rate of 3-5mm per day

Question 13

how are mares estrus behaviour assessed using teaser stallions

Answer 13

Score 0: mare aggressive, kicking etc

Score +: mare interested in teaser

Score ++: mare everts clitoris (‘winking’)

Score +++: mare quickly interested in teaser, winks and passed urine

Score ++++: mare stands with legs apart and urinates clear-cloudy urine

Question 14

when does the maximum preg rate occur

Answer 14

bred within 48hrs before to 6 hrs after ovulation

Question 15

how is timing of breeding assessed

Answer 15

Days from last ovulation

Cervix/uterine tone

Uterine edema

Size of follicle

Softness of follicle

Shape of follicle

Historical information

Estrous behaviour

Question 16

what are the 3 main methods of pregnancy diagnosis

Answer 16

Assessing behaviour by daily teasing

Measuring hormone levels in blood sample from mare (presence MAY indicate pregnancy)

• Progesterone (persistent CL or pregnancy)
• Equine chorionic gonadotrophin (large variation)
• Estrogen (later in preg, uncooperative mares, minis)

Ultrasound exam

Question 17

why must early pregnancy diagnosis be done

Answer 17

Identify non-pregnant mares as soon as possible

Must know if she is carrying twins

Question 18

when can pregnancy be diagnosed using US

Answer 18

day 11

5-8mm

first scan usually 14-15d

Question 19

what are features of pregnancy in a rectal exam

Answer 19

Uterus swells in pregnancy and rectal examinations can monitor increases in swelling

By 16 days no swelling palpable, but uterus becomes more tubular and turgid

Question 20

on day 23 what can be seen on US

Answer 20

White structure 4mm in length

Heartbeat seen as rapid flickering in the middle of the embryo

Question 21

what can be seen on day 25-28 on US with pregnancy

Answer 21

Check for normal development and no twins

About size of billiard ball at 30d

Question 22

how large is the fetus on day 50

Answer 22

50d a large tennis ball

Question 23

when else would you check a pregnant mare using US

Answer 23

Day 34

Extra exams needed if mare has cysts or is prone to pregnancy loss

Checked again in autumn to make sure still pregnant

Question 24

why is twinning undesirable

Answer 24

Abortion is usual outcome

• Often late in gestation at 7-8 months

Distressing for mare and owner

Mare can be difficult to get pregnant in same year in which she aborts

Rarely carried to term, unlikely to both survive

One usually small, rarely performs as athlete

Dangerous for mare

Question 25

how is twinning treated

Answer 25

At days 15, one pregnancy can be massaged away from the other by gentle pressure from transducer or fingers

Once spheres moved apart one can be crushed

Only light pressure needed

If pregnancies fixed together (after day 16) the success rate of crushing is reduced

In most cases both pregnancies lost

If both pregnancies lost before 35 days

• Mare usually back into heat within 10 days

After day 35 the mare will not come back into heat even if both pregnancies lost due to production of eCG by endometrial cups