The mare

Question 1

When does the mare begin puberty?

Answer 1

12-24 months old

Question 2

What are the two main phases of the mares oestrus cycle?

Answer 2

Folicular - Oestrgen dominant

Luteal - Progesterone and PG dominant

Question 3

How long is the oestrus cycle of the horse?

Answer 3

21 days

Question 4

Describe the breeding character of the horse.

Answer 4

Long-day breeders - summer and autumn

Seasonal polyoestrus

Anoestrus over winter

Transitional periods at the beginning and end of the season

They cycle from puberty to death

Question 5

How long does oestrus last in the horse?

Answer 5

4-6 days

Mare becomes unreceptive to the stallion within 12-24 hours of ovulation

Question 6

How large does a dominant follicle have to be for ovulation to occur?

How does it induce oestrus?

Answer 6

>35mm diameter

The follicle produces oestrogens

Question 7

Outline what happens in the luteal phase of the oestrus cycle.

Answer 7

The ovulated site becomes a CH and then a CL which produces P4

The CL is at first resistent to PG but after 15days becomes sensitive and luteolysis occurs

After this follicular waves begin to develop and oestrus occurs (2 waves before dominant follicle selected)

Question 8

In a transitional period mare what would be seen on an ultrasound of the ovary?

What happens to these structures?

Answer 8

Multiple small follicles (10-25mm)

These follicles will not ovulate and regress - mares in this period may show off oestrus behaviour and will not concieve if mated

Question 9

How long can the transitional period last?

Answer 9

Up to 6 weeks

Question 10

Induces luteolysis if a receptive CL is present on the ovary

Answer 10

Exogenous prostaglandins

Oestrus will comence 3-5 days post injury

(may cause sweating, d+ or colic signs)

Question 11

Supresses oestrus, withdrawal of treatment leads to a rebound in ovarian activity.

Answer 11

Progestagens

Question 12

Induce signs of oestrus (not true) and used in teaser mares for AI collection.

Answer 12

Oestrogens

Question 13

Induces ovulation of a dominant follicle within 24 hours of administration.

Answer 13

Human chorionic gonadotrophin (chorulon)

Acts like LH

Question 14

A GnRH analogue which induces ovulation in 48 hours.

Answer 14

Deslorelin

Question 15

How manipulation of photoperiod be utilised in promoting ovian cyclicity of the horse?

Answer 15

Extending the recieved photoperiod to 16 hours (8 hours of dark)

30 minutes extension on either end of the day 2-4 weeks before the summer solstice

Ovulation occurs 8-10weeks later

Question 16

How long is equine sperm viable within the reproductive tract of the mare?

Answer 16

48 hours

Question 17

When should you serve a mare? Why?

Answer 17

24-48 hours prior to ovulation

Sperm are viable for 48 hours in the mares reproductive

Oocyst is only viable for 12 hours post ovulation

Question 18

How does a mares uterus and ovary appear on ultrasound when she is in oestrus?

Answer 18

Dominant follicle on one ovary

Uterine oedema

Soft oedematous cervix

(remember behavioural signs)

Question 19

You scan a mare and find she has a 35mm DF on the left ovary and uterine oedema.

When you next scan her and why?

Answer 19

In 24-48 hours to check if she has ovulated

Question 20

You scan a mare and find ms follicles on the left ovary and a CL on the right. There is no uterine oedema present.

How would you progress?

Answer 20

PG and rescan in 3-5 days - when she comes back into oestrus

Question 21

You scan a mare and find a 35mm follicle with a “pointed” edge.

How would you progress?

Answer 21

Breed her!

The pointed DF suggests she is about to ovulate

Question 22

Describe the changing formation of uterine oedema during oestrus.

Answer 22

1. Oedema forming
2. Oestrus = catwheel oedema
3. Oedema decreases in 24 hours prior to ovulation

Question 23

A post mating scan 24-48hrs after mating is useful why?

Answer 23

Check only 1 ovulation has occurred

Check she has ovulated

Checking for fluid in uterine lumen (endometritis

Question 24

What three seals prevent bacterial contamination of the uterus in the mare?

Answer 24

Vulval

Vestibular

Cervix

Question 25

Answer 25

An example of poor perineal conformation - can lead to pneumovaginum, urovaginum, cervicitis and endometritis

Tx by caslicks vulvoplasty (10-14day sutures)

Question 26

Which pathogens are associated with chronic endometritis?

Answer 26

• Strep. zooepidemicus
• E.coli
• Pseudomonas
• Klebsiella
• Occasionally yeast/fungi
• Taylorella (CEM)

Question 27

How would you treat endometritis in the mare?

Answer 27

Uterine lavage

Oxytocin

Antibiotics - ceftiofur

Question 28

What type of swab should be used in isolation of CEM?

Answer 28

Charcoal amies

Question 29

Contagious equine metritis is caused by what bacteria?

Answer 29

Taylorella equigenitalis

Question 30

What are the three different types of endometritis?

Answer 30

• Contagious - E. coli, Kleibsiella, CEM
• Free fluid - due to uterine oedema during ostrus (good medium for bacterial growth)
• Mating induced - semen is inflammatory, also bacteria from stallions penis

Question 31

Chronic degenerative endometrial disease

AKA endometrosis

Answer 31

A progressive degeneration of endometrium and its replacement by fibrotic tissue.

Begins age 17 - major cause of age related infertility

Question 32

Causes of cervical incompetence.

Answer 32

Congenital

Foaling injury