Mare Reproduction Flashcards
In which part of the ovary will ovulation ALWAYS occur in the mare?
The ovulation fossa
What is the length of the mare’s oestrus cycle?
21-22 days
WHat is the timing of ovulation in the mare?
1-2 days before the end of oestrus. A small percentage of mares will ovulate after oestrus.
What cyclic seasonal changes do mares go through?
Vernal transition –> Breeding season –> Autumn transition –> Anoestrus
Ovulatory follicles in mares range in size from what to what?
35 - 70mm diameter
List behavioural characteristics displayed by a mare in estrus:
- Raising tail
- Squatting
- Urinating
- Everting clitoris (winking)
WHich hirmone would you test for to determine a mare is in diestrus?
Progesterone
What are two methods of artificial lighting to bring forward the onset of estrus?
Constant lighting: 14-16h a day - lights on until 10pm
Intermittent lighting: 1hr of light during the night (10h after onset of dark)
What is the aim of treatment with a dopamine antagonist such as domperidone in the lead up to estrus?
To increase prolactin secretion -> increased LH receptors on ovary
How many days post-ovulation is the corpus luteum responsive to PGF2-a
How can you improve fertility at foal heat?
Delay heat by administering altrenogest from day of foaling for 8 days, then give PGF2-a injection on day 9
OR
Skip foal heat then give PGF2-a 6 days post ovulation to ‘short cycle’ the mare
Recommend methods for inducing estrus in anoestrus mares:
- artificial lighting
- dopamine antagonists
- GnRH
- progestins
Recommend methods for synchronising estrus:
- Terminate the luteal phase (PGF2-a)
- Lengthen the luteal phase (progesterone)
- Induce ovulation (hcg / deslorelin)
- Inhibit follicular development
Recommend methods for inducing ovulation:
*must mimic the LH surge in presence of mature enough follicle (>35mm)
- hCG
- Deslorelin
Recommend methods for suppressing estrus:
- Hormonal (progestins - work within 1 day)
- Surgical (ovariectomy - permanent)
- Immunological (GnRH vacc - lasts for 1yr, not recommended if breeding in future)
- Abortion after formation of endometrial cups
- Galss marbles in uterus???
What are the advantages of using AI in mares?
- access to a wider rage of stallions
- disease control / reduced contamination
- safety
- prevents overuse of stallion
- more regular semen evaluation
What is a major disadvantage of AI in horse?
Thoroughbreds cannot be bred by AI
What components are included in semen extendors?
- buffers
- energy
- proteins
- antibiotics
What is the goal time period for insemination with frozen semen?
12h before to 6h post ovulation
Approximately how long after a hCG / deslorelin injection does ovulation occur?
~36h
What advantages does embryo transfer offer?
- Enables breeding at earlier age
- Production of offspring from endangered species
- Pregnancies from mares still in competition
- Potentially >1 foal per mare each year
- Removes risks of foaling in valuable mares
When does the reciepient mare need to ovulate for embryo transfer?
Needs to have ovulated 1 day prior or up to 3 days after the donor mare
List some ultrasonographic signs of early embryonic loss:
- irregular shape of embryonic vesicle
- prolonged mobility of vessel (>day 16)
- excessive endometrial oedema
- fluid within uterine lumen
- undersized embryo for age
- no heartbeat by day 30 / loss of heartbeat
Is hydrops amnion or hydrops allantois more common in mares?
Hydrops allantois
