Equine Reproduction Flashcards by Leah Arth

Overview

foals should be born in spring/summer optimally
Arbitrary artifical birthday depending on hemispheres
if you have a foal that was born in August it is going to look better for sales (echo)
Sports horses: depends on how it fits into that schedule

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Mare Reproductive Anatomy

3 gateways to the mares trct: cervix, vaginal vault, perineum
means there are 3 stops for bugs

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Mare Anatomy

(Ovary)

will be rather small if there is no activity (walnut)
stimulated through puberty and then cycling
Follicles: you will be able to be able to feel the little bubbles
It will always rupture from the ovarian fossa (this is important for harvesting!)
echo
*

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Mare Anatomy

(Uterus)

long horns and a reasonsably short body
T or Y: important for the implantation of the embryo and harbor for disease
echo
broad ligament can be a spot for hemorrhage during foaling difficulties

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Mare Anatomy

(Cervix)

in ponies it is about 4cm
anoestral cervix has tone to it, but no color
oestral cervix: osebud appearance and becomes a wiltered rosebud appearance as it gets closer to ovulation (melting into floor of vagina)
Dioestral: after ovulation, more tone to it and then under the influence of the pregnancy it is a tight fist

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Mare Anatomy:

Perineum

First stop to prevent infection
need to look at these areas for pre-breeding swabs
remember this orientation and with multiparous mares this becomes altered and then you run into issues with infections and such

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Breeding Season and Oestrus Cycle

Throroughbreds: earlier in the year
polar ponies: later in the year
sports horses: usually in the middle of the year
Generally April, May, June
want to increase day length if we can as it has a lot of effect on their cycle

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Influences on Breeding Season and Oestrus Cycle

stimulate the hormones from the brain that we need to move forward
green grass effect: stimulation to try and enhance (?)

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Hormonal Pathway

melatonin in the spring time drops and that stimualtes the GnRH release in the hypothalamus (which we can alter sometimes)

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We need this feedback of estrogen to have that necessary LH surge

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Transitional Period

this is the part we are trying to move forward in terms of cycling for thoroughbreds
depends on hemisphere!
Want to kick ovaries into action to get early oestrus cycle
We know we can manipulate the light
Dopamine can be applied to fire them out of the transition stage

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Oestrus Cycle

There are only a few days when they are ready to stand (then you are talking about AI or naturally breeding)

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Oestrus Cycle: Hormones

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Oestrus or Follicular Phase

follicular development
mares are starting to show signs they are ready to be mated
uterus under the influence of oestrogen will become oedemetous (wet woolen sock)

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a bunch of small follicles
then start to get one big decent sized dominant follicles and then shut the rest up
If we have more than one dominant follicle, there is potential for twins which is not ideal for horse repro
follicle goes towards ovulation fossa and then shoots egg into fallopian tube

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Oestrus: Follicular Development

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Oestrus: Ovulation

some mares will want to ovulate at a 5cm follicle which makes it hard to mate with a stallion
Once an ovulation has occurred, we have a corpus haemorrhagica that forms and then become CL to produce progesterone

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Oestrus: Ovulation Hormones

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Oestrus: Uterus

oedematous: wet woolen sock
closer to standing oestrus: you will get fluid accumulating in the lumen (more than 2 cm is excessive)
fluid usually reduces just before ovulation

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Dioestrus or Luteal Phase

usually a window of 24-48 hours before the cervix closes
we can also manipulate the lysis of the CL –> IMPORTANT

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Manipulation of Oestrus Cycle

(transitional phase)

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Manipulation of Oestrus Cycle

(dioestrus)

When you know you have your corpus hemorrhagica that is day 1
can give PGF2a 7 days later?
this is a powerful hormone - so they need to know what they are doing and know how to give properly
it can really affect horses and people as well!
You will get sick if you accidentally jab yourself with this
never to be used if anyone thinks they are pregnant!

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Manipulation of Oestrus Cycle

(Dioestrus- Prolonging or support of dioestrus)

progesterone can have adverse effects on people as well
*

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Manipulation of Oestrus Cycle

(Inducing Ovulation)- HCG

mimics LH surge
nice water base- and mix it up with solution
quite handy
not good for older mares as they tend to not respond well and may get used to it with multiple applications

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Manipulation of Oestrus Cycle (Inducing Ovulation)- GnRH agonists

* echo * choron may be good for frozen semen * throughbreds take a bit longer to get to the mare so it may be better to use this instead??

Reproductive Abnormalities: Ovary

* Anovulatory follicle can even get up to 10 cm * these are not the same as a follicular or ovarian cyst! * Just a follicle that hasn't had the urge to push it, will over time eventually rupture * they may be painful * The horses may be misbehaving due to improper hormones * **Granulosa Theca Cell Tumor:** not to be confused with your corpus hemorrhagica * some of these could get massive before we caught them with scanning (basketball size) * probelm is that they produce inhibin - echo (will end up surpessing the other ovary and) * Now there is a hormone we can use against it

Reproductive Abnormalities: Uterus | (endometritis)

* because it is vascular, we end up with bugs there * endometritis is a common thing among mares * as mares get older they lose their immunity in the endometrium * the ones we need to be aware of as a vet is CEM, Kebsiella, Pseudomonas * Infection is goign to keep that cervix open as it want to clear something out --\> will drive her to continue showing oestrogenic signs * can have persisitent fungal ones as well!

Reproductive Abnormalities: Uterus | (post breeding endometritis: Treatment)

* Not every mare needs a lavage, but a lot of them it helps * The one we use more often is Ceftiofur * myometrium (muscular layer) - want that to contract to get fluid out --\> oxytocin (also allows for milk letdown!) * Corticosteroids: something we are starting to use after ovulation to reduce inflammation

Reproductive Abnormalitites: Uterus | (chronic endometritis/endometriosis)

Endometriosis- Kenney Scale

* healthy uterus at top and then decreases

Reproductive Abnormalities: Uterus | (3)

* top right: endometrial cysts--\> can easily be confused for pregnancy! * or you can have a cyst and pregnancy and confuse for twins * middle: foreign body in the uterus (uterine marble) - often get left there! --\> leave an acoustic shadow * can even find broken off swab tips * uterine adhesions

Preliminary Considerations for breeding a mare

* what they are going to do and when * breed for a defined birth date * depending on function * Thoroughbreds are always natural breeding

Breeding Soundness Exam

* echo * baby with a young horse pelvis - if you are trying to breed them, may run into dytocia risk * no point in breeding a mare that is struggling to manage its own body weight

Code of Practice- Obligations | (Notifiable/Non-notifiable)

* EIA: is not in the UK (exotic), any of the horses that have it should not be allowed to have it, but it IS in europe * echo * CEM: can sometimes show up as random positives, is notifiable!

Code of Practice- Obligations | (testing)

* EVA and EIA - need to know she is clean before she goes to the stud * important to swab * If she cycle and misses, you just need to redo the endometrial swab

Clitoral Swab

* either do PCR or culture (takes longer- 7 days) * swab needs to be in date * PCR is not acceptable for horses going into USA - need to do a CEM and have it be frozen?

HBLB Testing: Mare Requirements

* If they have endometritis from another bug, this is not going to pick it up * It will only pick up those 3

HBLB Code of Practice: Additional Requirements (EHV3)

* can be transferred via fomites (sponges) * highly contagious

HBLB Code of Practice: "Genital Glanders"

* something we don't test for with local breeding, but if they are traveling * more concerned for horses coming from the far side of europe

HBLB Code of Practice | (Strangles: Streptococcus equi)

Pre Breeding Exam

* can use bales (put something between you and the horse!) * sedated mares will kick you a lot faster and harder as they are not aware, it is just a reflex! * You need to sedate a horse efficiently to coduct an exam efficiently * particularly young mares don't have a lot of room, you need to be cautious - if they are straining, let off a bit

Pre Breeding Exam | (External genitalia)

* benched appearance: when she defecates, it will go right into the vulval area * we can create an artificial seal

Pre Breeding Exam: Ultrasound

* dominant follicle--\> thickening --\> CL

Pre Breeding Exam: US | (Uterus)

* orange pattern tells you have an oestrus uterus

Pre Breeding Exam: US | (Uterus Abnormalities)

Pre Breeding Exam: US | (record findings)

* can do different things, but need to keep some sort of record! * need to have a record of what you do as well

Pre Breeding Exam: Cervical and Vaginal Exam (Vaginal Speculum)

* now do a speculum exam * need to clean all the crevices (clean hand/dirty hand method) * do not want to create an iatrogenic infection * oestral cervix: red and oedemetous * porr conformation can really end up with secondary infection * dioestral cervix can mean she might have a CL which will affect her being in true oestrus - give PGF2a and then she may stand more effectively

Pre Breeding Exam: Endometrial Swab

Pre Breeding Exam: Endometrial Swab | (steps)

Breeding Plan

* vaccinations and swabs pass * point now is going to be working out when you are going to be able to breed her * we know our oestrous is goign to be 5-7 days * some mares reliantly put up more than one follicle, we need to keep record of that in the case of possible twinning

Breeding PLan (2)

Post overing Exam: see what follicles have ovulated and if there is none it is best to remate her

Breeding: Natural Cover

* mares can get really badly hurt as they don't know what they are doing and arent cycling properly *

Breeding: Natural Cover | (disadvantages)

* everyone is more potentially at risk * some stallions are not nice to cover * mare with young foals, they become extra --\> need to remove the foal (but then the mare performs badly)

Breeding: Foal Heat

* need time to reorganize --\> too soon would lead to a poor conception rate * If mares miss the first couple of cycles - their foals are getting later, later and later

Natural Cover vs. Artificial Insemination

* Everyone wants to blame the mare with failed AI's but often it has to do with transport

Artificial INsemination: Chilled Semen

* want to get it chilled down and shipped * semen is incredibly sensitive! --\> need to put in an extender * forzen semen doesnt last as long * If it has spent too long in transport, it will begin to slowly die as the packs melt