Therio- Assisted Reproductive Techniques in the mare

drraythe's version from 2016-04-29 14:36

Intro + embryo transfer

Question Answer
assisted repro techniques in horses are most often used with what horses?polo ponies
4 most common ARTs used in horses? (2 that aren't commercially avail are?)(1) embryo transfer (ET) (2) Oocyte transfer (OT) (3) Intracytoplasmic sperm injection (ICSI) (4) Cloning/Nuclear transfer (NT) ( then also Not commercially available in horses:Gamete intrafallopian transfer (GIFT) and In vitro fertilization (IVF) )
4 common indications for why youd want to o embryo transfer (ET) on a mare?(1) Obtaining foals from performance & show mares while they’re still competing (2)Obtaining multiple foals from the same mare (3) Obtaining foals from mares with non-reproductive health or musculoskeletal problems (4) Obtaining foals from mares with reproductive problems
if you Want to have RECIPIENT mares with normal reproductive cyclicity in early February (N. Hemisphere) when do you need to start them on light therapy?Need to start on good artificial lighting program in mid-November
what are some things you need to look at/be aware of to make sure the RECIPIENT mare is repro. sound?need udder to be sound, test for EVA, needs to be 3-12 yrs of age with good perineal conformation!
along with having a good teasing record for your RECIPIENT mare, you need to establish her exact day of ovulation by... (couple things)Rectal palpation, Transrectal ultrasound
**what number "day" is considered the day of ovulation? days after? DURING WHAT DAYS ARE MARES considered eligible to receive embryos?ovulation= Day 0. The next day would be +1D, the next +2D, etc. the window +4 to +8 days is when she is eligible to recieve embryos
what are 2 options for having recipients ready at exactly the right time?(1) Estrus synchronization of recipients & donors (2) Have a herd of recipients and find one that has ovulated at a similar time to the donor (done in Argentina/South America)
**how many recipient mares do you need per donor?Need at least 3 recipient mares/ donor
*how do you super-ovulate a mare?TRICK QUESTION: you cant! they have an ovulation fossa which limits their ability to ovulate
which agents are given to cause a DONOR mare to ovulate? how big must the follicles be?hCG or GnRH given to induce ovulation when follicles greater than or equal to 3.5cm
what might you be able to use to inc ovulation rates in mares?Sometimes may use purified equine FSH (eFSH) to increase ovulation rate in mares
***when are DONOR mares flushed after ovulation?Donor mares are flushed on D7 (D6-D8) after ovulation (Eg. If ovulated on Monday, she’s flushed the following Monday)
so during the week between when the DONOR ovulates and when she is flushed, what should you be doing?Keep mare as stress-free as possible, In older mares, consider altrenogest supplementation daily
for the embryo transfer, the best results are when the RECIPIENT is ovulated WHEN? (compared to the donor)Best results obtained if recipient ovulated 1 or 2 days after the donor (ie. +5d or + 6d with donor flushed on +7D after her ovulation) (so, want recipient a day or so behind the donor)
how do you insert the egg into the recipient (what tool) and what precautions must you take?Embryo loaded into a straw, then you are Passing a cassou insemination gun through closed cervix (diestrus)!! SINCE THE CERVIX IS CLOSED BC SHE IS IN DIESTRUS, you need to be very careful not to disrupt or dilate or upset it, or you can compromise the preg
what can you give the recipient mare to help maintain the preg after you insert the embryo? for how long?Mare often placed on altrenogest until D60 of pregnancy (progesterone) (hey, D60 is when feto-placental unit takes over maintenance)
how do you load the embryo into the straw for insertion into the the recipient mare?want to load it so there is a little bubble on each side of it to keep it in place
post-transfer of the embryo, the recipient mare is Monitored frequently until... (day?) what are they monitoring for?D50, monitor for endometritis & checking CL
how successful is embryo transfer resulting in a foal born?On average 1 foal per 3 inseminations
Pre-implantation genetic testing is often done....what are some things that are usually being looked at?Gender (they want female polo ponies) color, arabians (Color Coat Dilution Lethal Syndrome or Lavender Foal Syndrome, SCID), Hyperkalemic Periodic Paralysis Disease (HYPP) in Quarter Horses, as well as other things
what are two dzs which ARABIAN horses have Pre-implantation genetic testing done for?(1) Color Coat Dilution Lethal Syndrome or Lavender Foal Syndrome (2) Severe Combined Immunodeficiency (SCID)
what dz which QUARTER horses have Pre-implantation genetic testing done for?Hyperkalemic Periodic Paralysis Disease (HYPP) in Quarter Horses
how soon after the embryo has been developed can Pre-implantation genetic testing determine the gender?6hrs! testing will have No loss of viability
what is Severe Combined Immunodeficiency (SCID)? Which breed gets this? what happens?Autosomal recessive trait in Arabian horses. Fatal condition of both B & T cell dysfunction. Foals susceptible to all pathogens (eg. Viral, bacterial etc).... Foals appear normal at birth, but rapidly develop fatal septicaemia
Lavender Foal Syndrome--> who gets this? what happens?(aka Coat Colour Dilution Lethal), Recessive gene mutant in Arabian bloodlines. Foals have difficult delivery, struggle to stand. You will see Episodes resembling seizures with limb extensor rigidity. Usually euthanized within a few days of birth
when can you sex foals with U/S? How? (timing?)Ultrasound @ 65 days of pregnancy! The female genital tubercle/clitoris will be closer to the tail head
why does embryo sexing matter so much with polo?Very strong preference for fillies for competition (90 % of polo foals born this year are fillies). Gender determination at 65 days and only female pregnancies are maintained (Prices: no selection $2,500$ / only filly $4,500)

things that aren't embryo transfer

Question Answer
why might there be OOCYTE transfer instead of EMBRYO transfer?Only if standard ET not an option because of problems with donor mare's cervix, uterus or uterine tubes that precludes fertilization or causes EED before D7 (Eg. Chronic endometritis, pyometra, cervical damage)
what are two ways to harvest the oocyte from the donor mare?(1) Transvaginal ultrasound guided aspiration (TVA) (2) Puncture of the follicle via a needle placed in the flank
for oocyte transfer, donor and recipient are Both induced to ovulate with what? at the same time or diff times?SAME TIME, induce with hCG or GnRH
oocyte transfer--> how long after ovulation are oocytes aspirated-- and WHO'S oocytes are aspirated?Oocytes from both mares aspirated 24-35 h after induction of ovulation
oocyte transfer--> once oocytes from both mares have been aspirated, how do you do oocyte transfer?Recipient is inseminated with semen from desired stallion--> Donor mare’s oocyte transferred via standing flank laparotomy to oviduct of recipient. Can also be used for ICSI (see later)
how does Transvaginal ultrasound guided aspiration (TVA) work?
how does Intracytoplasmic sperm injection (ICSI) work?Method by which one sperm is picked up (they have to swim through a filter, so the non-motile ones are left behind) with a micromanipulator microscope and injected into the oocyte. This is a good method for oocytes collected by flank puncture or transvaginal ultrasound (TVA) (50% pregnancy rate per mare per aspiration session)
Intracytoplasmic sperm injection (ICSI)--> after the oocyte has been fertilized by this method, what are 3 options of what to do with it after?(1) Immediate surgical transfer into the uterine tube of mare (2) Culture for 24/48 h and then transfer into uterine tube (3) Culture for 7-8 days and then transfer into uterus as for standard ET.
Nuclear Transfer/cloning is banned in who?Banned in Thoroughbred and Quarter Horses (Mainly used in polo ponies) ($150 000/foal!!)
Are clones genetically identical?Yes and no... chromosomal DNA the same but not the mitochrondral!
what is going on with Gamete Intrafallopian Transfer (GIFT)?Technique of transferring both oocytes and sperm into the uterine tubes (Not currently commercially feasible)
In vitro fertilization (IVF)--> what is done with this process, and WHY is it NOT used in horses?this is when there is Incubating oocytes with sperm for fertilization in vitro (ie. Outside the body). Equine embryos have a glycoprotein capsule which sperm are unable to penetrate in vitro! (Also makes cryopreservation of embryos difficult) Therefore IVF not currently used in horses