Main repro features and traits of the horse (breeding season, raising foals) Flashcards
time of puberty and full sexual maturity
puberty occurs btw 16 - 18 months (late puberty).
full sexual maturity reached by 2+ years (avg. 3-5yr)
what is uniparous?
produce single offspring at birth
general repro features incl:
repro potential,
seasonality,
pregnancy rate.
low repro potential,
seasonal sexual activity: polyoestrus,
low pregnancy rate,
frequent miscarriages,
uniparous.
when is the equine breeding season and when is fertility highest?
Feb - Aug.
highest: march - june.
cycle length of mare?
monophasic or biphasic?
luteal phase present?
20 - 21 days,
biphasic,
with a luteal phase.
When does ovulation occur, how many eggs are released?
Occurs spontaneously,
During late phase of heat (on the 4th or 5th day),
1 or maybe 2 eggs will be released.
Do twin ovulations occur and what is the outcome if they do occur?
Twin ovulations rarely occur,
Usually there is resorption or abortion (30%),
A rare and undesirable occurrence - one embryo normally pinched.
Definition of corpus luteum
Mass of cells that form in an ovary and is responsible for the production of the hormone progesterone during early pregnancy.
When can heat be induced in mares
When the corpus luteum in mature
When does heat (oestrus) occur
It lasts 3-5 (7) days,
Foal heat can occur the 9th day after foaling, 50% chance of fertility.
Signs of heat in mares
Relaxed, Hyperaemia in external genitals,
Frequent urination,
Raising tail,
Mucous discharge,
Desire for company,
Presenting to teaser stallion.
Mention 2 forms of practical heat detection
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).
x4 cycling disorders
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.
What type of covering is required for thoroughbred breed?
Must be live cover.
Describe process of artificial insemination
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.
What is the semen motility and conception rate of AI?
Semen motility of 50% is successful.
Conception rate = 60-80%
Advantages of AI
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.
What is the gestation period of a mare and what maintains the gestation period?
Length: 336 (326 - 350).
Maintained by: accessory corpus luteum,
eCG (PMSG) production days (31 - 120),
Placenta oestrogens (4th - 5th month onwards)
Where does fertilisation occur and when does the embryo migrate?
Fertilisation: in Fallopian tube.
Embryo migrates to uterus after 4-5 days.
When does implantation occur?
When do longer pregnancies occur?
Implantation: around 40 - 50 days.
Longer preg are common in earlier mating season.
x4 forms of pregnancy diagnosis
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
What is pseudopregnancy and when does it occur?
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.
X3 environmental factors effecting repro
Photoperiod,
Condition of animal,
Hormones
How does the photoperiod effect cycling?
Increased daylight = increased ovarian activity.
What hormones effect cycling?
hCG/ GnRH induce ovulation.
PGF2alpha, gestagens, (regu-mate, PRID) induce oestrus.
Name x3 advanced repro techniques and why they are used
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.
