Therio- Comparative anatomy & Reproductive Physiology of the mare 2

drraythe's version from 2016-04-29 14:30

estrus synch

Question Answer
4 reasons you'd wanna do estrus synch?(1) Fixed time breeding (2) AI (Fresh-chilled or frozen-thawed) (3) Stallion availability and management (4) Embryo transfer (Donor & recipient management)
what big no-no should you know about AI?AI is NOT ALLOWED in thoroughbreds!
which three types of drugs can you use for doing an estrus synch?(1) Progestagens (2) Progestagens and estradiol (3) PGF2 α
why do progestagens work for synching estrus?mimics the luteal phase ie. diestrus. So, exogenous progesterone suppresses LH (when you remove this, then they go into estrus all at the same time)
progestagens are usually given in what medium, and what does this mean in terms of admin?P4 in oil (NB! injection site reactions)
If you are using P4 (progestagens) alone for estrus synch, how long must you do this for and why?Tx for 14-18d to ensure regression of previous CL--- Otherwise use in combination with PGF2 α on last day of treatment
Progestagens for estrus synch--> when would you expect estrus after end of tx? ovulation? (What might change these time guidelines?)onset of estrus in 3-6 d, ovulation in 8-15 d. However, can get ovulation during Rx... results in prolonged lutual phase due to exogenous + endogenous P4
what can you do to decrease treatment interval for tx with progestagens?Can add PGF2 α @ end of P4 treatment (removes any CLs that might still be present)
why would you wanna synch with Progesterone AND Estradiol?P4 alone won't block FSH and follicular activity... Therefore add Estradiol to program (estradiol inhibits FSH-->suppressed follicular activity--> NO diestrus ovulations during treatment--> improves synchrony)
how long do you tx with progesterone and estradiol, and what route of admin?10d, in oil IM
how long would you wait for ovulation to occur after stopping a progesterone+estradiol tx regimen?ovulation in 10-12 d (can include PGF @ end of Rx to improve synchrony)
WHEN can you start to use PGF2 α to estrus synch?CL responsive to PGF 2 from D 5-12
if you give PGF2a at the proper time (from D5-12) how long until youd expect estrus? ovulation?estrus in 2-4 d, ovulation in 7-12 d
natural vs synthetic PGF2a- whats the big whoop? (names for the synth vs natural)Synthetic (estrumate) is MUCH more potent, so need WAY less! (AND!!! horses are super sensitive to PGF to begin with as compared to cows, so REALLY need less) (natural is lutalyse)
May get variable response to Rx with PGF2α...why? (4 reasons)(1) CL refractory < D 5 (2) spontaneous ovulation > D12 (3) diestrus ovulation & therefore immature CL (4) follicle >/=3.5mm present @ Rx - may cause ovulation
what are dosages like of natural (lutalyse) versus synthetic (estrusmate) PGF2a?NATURAL is "Lutalyse" (Dinoprost-original) which is 10mg IM (1-2ml/horse). The SYNTHETIC is "Estrumate" (cloprostenol) 250ug IM (0.5-1ml/horse) (<----smaller amt bc synth more powerful!!)
what are side effects if you give too much PGF2a??sweating, colic signs, ataxia, ABORTION in pregnant mares & humans

Ovulation Induction

Question Answer
what are the three drugs avail for ovulation induction?(1) hCG (Human Chorionic Gonadotropin) (2) GnRH (3) PGF2 α
how does hCG work to cause ovulation induction?LH-like effect => ovulation
what are the necessary prerequisites for hCG to work to induce ovulation?>= 35 mm follicle (aka 3.5cm), D2-3 of estrus
why hCG and not eCG?bc eCG has a FSH like effect
once you give hCG (under the right conditions, ie 3.5cm follicle and D2-3 of estrus), how long till ovulation?ovulation within 36-48h
three GnRH products avail for induction of ovulation are..(1) Deslorelin (2) GnRH agonist (3) S/C implant (in vulva for ease of removal “ovuplant”) or aqueous solution (available overseas)
once you give GnRH, how long till you expect ovulation?ovulation within 48h
where do we put the SQ implant for GnRH...and why?vulvar we can find it easily again
why do you not want to leave GnRH in for too long?prolonged interoestrus intervals due to downregulation of FSH/LH axis THEREFORE remove implant!!! (basically switches off the whole cycle)
how does PGF2a cause induction of ovulation?Mechanical contraction of smooth muscle – ie. Capsule around ovary--> causes ovulation
What treatment was administered to the mare on 2nd May? PGF2a (short cycling to give during diestrus)

suppression of estrus

Question Answer
what are two reasons WHY you'd want to suppress estrus?(1) Competition horses (2) Riding horses
Permanent sterilization can be used as a way to suppress estrus...implications?Risks? Practicality, economics
two examples of Reversible Pharmacological ways of suppressing estrus?(1) Daily P4 (altrenogest) (2) GnRH agonists (deslorelin)
is immunocontraception reversible?yes
reversible immunocontraception--> what are the two ways you can do this?(1) pZP vaccine (Porcine Zona Pellucida) (2) anti-GnRH vaccines
pZP vaccine (Porcine Zona Pellucida) end result is that is does what, but doesnt do what?works as contraception, but DOESNT affect the estrus cycle (feral horse populations where NB! Hierachy)
how does anti-GnRH vaccines affect the horses? where is it usu used?suppresses reproductive function + behaviour. feral horses and deer populations currently (potential for abuse? Would affect all animals)

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