Breeding Horses

At what age can mares be bred?

from 2 years old (optimum at 5-6 years)

At what age do we see a marked decrease in fertility in mares?

15 years old

What is the optimal BCS in a mare at conception?

3

What must you do with a highly athletic mare before breeding?

observe a let down period in which you decrease her exercise levels for 1 month before breeding

What feature of a mare’s coat can tell you about her ovarian function?

the presence of a winter coat suggests this is not the right time of year for her to breed

What are the features of a mare’s perineum that must be correct to allow breeding?

vulvar, vestibular and cervix seals must all be intact to prevent infection of the reproductive tract

cranio-caudal vulva slope must be less than 10 degrees off vertical to prevent constant faecal contamination of the vulva lips

at least 0% of the vulva must be ventral to the dorsal ischial limit

Which oestrus strategy is used by the mare?

seasonal poly-oestrus

Which breeding strategy is used by the mare?

long-day breeders

How can lighting be used to control the oestrus of a mare?

extend light exposure to 16 hours per day by switching lights on 30 mins before sunset

must be the same every day

How long does it take for a lighting regime to have an effect on the oestrus cycle of the mare?

60-90 days

What considerations must be made when using a lighting regime to make a mare enter oestrus earlier in the year?

the changes may trigger the mare to lose her winter coat earlier and have a higher metabolic rate, and so must adjust husbandry

What happens during the spring transition of the oestrus cycle of the mare?

irregular oestrus behaviour

multiple anovulatory follicles can be seen when scanning

What are the features of a normal oestrus cycle in a mare?

lasts 21 days on average

oestrus lasts 3-7 days

follicle ovulates on ovulation fossa

ovulation occurs 24-48 hours before the end of oestrus

a second follicular wave is possible

How can you identify the development of a corpus luteum in a mare?

ultrasound scan is required to confirm the presence of a corpus luteum as it is not palpable

What is the average gestation length of a mare?

320 days

can vary 2 weeks either side

What are the impacts of the failure of a mare to conceive?

reduces her value as a breeding animal

she cannot be rebred that season if the pregnancy is lost after 35 days due to the development of endometrial cups which maintain high levels of PMSG for a while

reputation loss for the stud

if an infectious problem this can impact future fertility

Why are breeding horses often kept for a long time?

their value will increase over time if their progeny performance is good

How long after conception does fixation occur in the mare?

16 days

How long after conception does organogenesis occur in the mare?

40 days

How long after conception do endometrial cups form in the mare?

35 days

What happens if a pregnancy is lost before 40 days gestation?

the embryo undergoes embryonic death and is resorbed

What happens if a pregnancy is lost at 40-300 days gestation?

an abortion occurs

What happens if a pregnancy is lost after 300 days gestation?

the foal is stillborn

What usually happens when twin conception occurs in the same uterine horn (unicornual twins)?

one undergoes embryonic death and the remaining embryo develops and is born live

What usually happens when twin conception occurs in separate uterine horns (bicornual twins)?

both embyros develop into foetuses and are then aborted

this is often because one twin receives a larger portion of placental nutrients and so the other dies off at a later stage, releasing toxins and autolytic products which causes the death of the ‘stronger’ twin

What is the earliest that pregnancy can be diagnosed in the mare and how?

11 days after conception

via rectal ultrasound

How far into gestation can pregnancy be diagnosed via manual palpation in the mare?

20 days

How far into gestation can pregnancy be diagnosed via blood endocrinology in the mare?

40 days

What different aspects of breeding a mare incur cost?

transport to a stud

stud fee

groom and in-foal fee

veterinary fees

livery at stud

requires a foaling box and suitable paddock

takes time for care and management

loss of a riding horse during later stage gestation

What must be done for a mare before breeding according to the HBLB Code of Practice?

mare must be certified free of transmissible venereal diseases before arriving at the stud

culture must be done by an approved laboratory

results reported on an Official Laboratory Certificate

What happens to a mare while she is at a stud?

1. usually given PGF2a upon arrival at the stud to trigger luteolysis and get her into oestrus in the next few days

2. monitor oestrus by scanning ovaries and uterus, teasing with infertile stallions and monitoring cervical changes

3. shoes are removed to prevent chance of damage during mating

4. service occurs once oestrus is diagnosed

5. post-service check is performed 24 hours after

6. pregnancy diagnosis performed 16 days later

What happens to a thoroughbred that has been conceived via AI?

it cannot be registered for racing due to concerns about genetic diversity

What is done during a natural service?

vulva and penis of breeding pair are washed immediately before covering

mare is restrained (often tie one back leg to neck to prevent strong kicks to the stallion)

neck cover is placed on mare to protect against stallion biting

breeding roll can be used to prevent stallion from penetrating too deeply if there is a large size difference between the pair

At what age do stallions reach puberty?

12-24 months old

At what age do we start using stallions for breeding?

3-5 years old

What 5 key things would you look for to determine if a stallion will make a good stud?

libido

ability to mount and serve - no musculoskeletal problems

semen quality and quantity

free from disease

able to maintain condition and performance

What is a common problem in stallions?

obesity due to lack of activity besides breeding

this can reduce semen quality when fat is deposited in the scrotal sac as it affects temperature control of semen

What is the optimal BCS of a stallion when breeding?

3

What should make up the diet of a breeding stallion?

atleast 50% roughage

10% crude protein

vitamin A

How much food does a stallion consume per day?

2-3% bodyweight

How is semen collected from a breeding stallion?

1. stallion is teased with a mare in oestrus

2. penis is washed

3. stallion is presented to a mounting dummy/block

4. erect penis is deflected into handheld artificial vagina one stallion has mounted and is restrained

How would you expect a stallion to behave when introduced to a mare in oestrus?

immediate interest in the mare

erection occurs less than 2 mins afer contact

stallion is ready to mount 5-10 seconds after erection

ejaculation occurs after 5-6 pelvic thrusts

What is the approximate lifespan of fresh semen once inside the mare?

72 hours

What is the approximate lifespan of chilled semen once inside the mare?

36 hours

What is the approximate lifespan of frozen semen once inside the mare?

12 hours

What are the signs that a pregnant mare is getting close to parturition?

udder develops 3-6 weeks before

teats fill 7-10 days before

teat waxing occurs 6-48 hours before (wax droplets form)

pelvic ligaments soften 1-3 weeks before

vulva swells and relaxes within 24 hours of birth

drop in body temperature 4 hours before

milk electrolytes increase 24-48 hours before

milk pH decreases 24 hours before

progesterone increases and oestrogen decreases towards parturition

What time of day do mares tend to foal?

night time

How much should a healthy placenta weigh after parturition?

approx 11% of foal’s birthweight

What aspects of the mare would you examine after parturition?

check udder for milk

check placenta has been expelled and is of adequate size (appears inside out)

What aspects of the foal would you examine after parturition?

vigour

should move into sternal recumbency 1-2 mins after birth

should be on feet by 2 hours latest

suckle reflex should be shown 20 mins after birth

foal should be nursing 2-4 hours after birth

check navel

ensure colostrum transfer