Main repro features and traits of the horse (breeding season, raising foals)

Question 1

time of puberty and full sexual maturity

Answer 1

puberty occurs btw 16 - 18 months (late puberty).
full sexual maturity reached by 2+ years (avg. 3-5yr)

Question 2

what is uniparous?

Answer 2

produce single offspring at birth

Question 3

general repro features incl:
repro potential,
seasonality,
pregnancy rate.

Answer 3

low repro potential,
seasonal sexual activity: polyoestrus,
low pregnancy rate,
frequent miscarriages,
uniparous.

Question 4

when is the equine breeding season and when is fertility highest?

Answer 4

Feb - Aug.
highest: march - june.

Question 5

cycle length of mare?
monophasic or biphasic?
luteal phase present?

Answer 5

20 - 21 days,
biphasic,
with a luteal phase.

Question 6

When does ovulation occur, how many eggs are released?

Answer 6

Occurs spontaneously,
During late phase of heat (on the 4th or 5th day),
1 or maybe 2 eggs will be released.

Question 7

Do twin ovulations occur and what is the outcome if they do occur?

Answer 7

Twin ovulations rarely occur,
Usually there is resorption or abortion (30%),
A rare and undesirable occurrence - one embryo normally pinched.

Question 8

Definition of corpus luteum

Answer 8

Mass of cells that form in an ovary and is responsible for the production of the hormone progesterone during early pregnancy.

Question 9

When can heat be induced in mares

Answer 9

When the corpus luteum in mature

Question 10

When does heat (oestrus) occur

Answer 10

It lasts 3-5 (7) days,
Foal heat can occur the 9th day after foaling, 50% chance of fertility.

Question 11

Signs of heat in mares

Answer 11

Relaxed, Hyperaemia in external genitals,
Frequent urination,
Raising tail,
Mucous discharge,
Desire for company,
Presenting to teaser stallion.

Question 12

Mention 2 forms of practical heat detection

Answer 12

Live cover: mare is ‘teased’ several times with a teaser stallion - mares in heat will generally tolerate the teaser or present herself to him.

Veterinary determination: ultrasound/palpation/measuring hormone levels (luteinising hormone, progesterone).

Question 13

x4 cycling disorders

Answer 13

Anovulatory cycle - only follicular phase,
Persistency and atresia of follicles,
Prolonged cycles,
Short, split or silent heat - occurs in early and late season usually a sign of sterility.

Question 14

What type of covering is required for thoroughbred breed?

Answer 14

Must be live cover.

Question 15

Describe process of artificial insemination

Answer 15

Semen is collected using an artificial vagina and processed in a lab before freezing/transport and chilling.
Plastic catheter is used intrauterine for deposition of semen.

Question 16

What is the semen motility and conception rate of AI?

Answer 16

Semen motility of 50% is successful.
Conception rate = 60-80%

Question 17

Advantages of AI

Answer 17

Allows international breeding programmes,
Less stress on animals (less transport),
More mares can be mated to valuable stallions,
Allows line breeding (semen of stallion can be stored and used after its death),
No contact btw mare and stallion,
No accidents,
Decrease spread of ventral disease.

Question 18

What is the gestation period of a mare and what maintains the gestation period?

Answer 18

Length: 336 (326 - 350).
Maintained by: accessory corpus luteum,
eCG (PMSG) production days (31 - 120),
Placenta oestrogens (4th - 5th month onwards)

Question 19

Where does fertilisation occur and when does the embryo migrate?

Answer 19

Fertilisation: in Fallopian tube.
Embryo migrates to uterus after 4-5 days.

Question 20

When does implantation occur?
When do longer pregnancies occur?

Answer 20

Implantation: around 40 - 50 days.
Longer preg are common in earlier mating season.

Question 21

x4 forms of pregnancy diagnosis

Answer 21

Non return: no heat after mating/AI,
Clinical signs: vaginal + rectal observations/palpating, thick mucus discharge, asymmetric uterus, fetal fluid+ foetus felt on facial exam.
Hormonal measurements: eCG, progesterone, estrogens, rapid tests, placental oestrogens in late pregnancy.
Ultrasound: after 14-15 days can see spherical embryo, vitelline veins, yolk sac and allantochorion

Question 22

What is pseudopregnancy and when does it occur?

Answer 22

A False pregnancy involving prolonged luteal phase and normal eCG production.
Due to embryonic death after 35days.
Cannot induce heat as corpus luteum does not respond to drugs.

Question 23

X3 environmental factors effecting repro

Answer 23

Photoperiod,
Condition of animal,
Hormones

Question 24

How does the photoperiod effect cycling?

Answer 24

Increased daylight = increased ovarian activity.

Question 25

What hormones effect cycling?

Answer 25

hCG/ GnRH induce ovulation.
PGF2alpha, gestagens, (regu-mate, PRID) induce oestrus.

Question 26

Name x3 advanced repro techniques and why they are used

Answer 26

Why: owner does not want to take valuable mare out of competition or training to carry a foal.
Embryo transfer,
Gamete intrafallopian transfer (GIFT),
Egg transfer.