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Control of Repro= HORSE (General Info (Follicle Growth (Grow in waves,…
Control of Repro= HORSE
General Info
Seasonally polyoestrus, fertile in spring
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Want foals born ASAP after 1st August (TB), 1st Sept (SB) so well-grown by sale
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Follicle Growth
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Follicle deviation when largest follicle 21-23mm, continues to grow at 2-3mm /d unti 1-2d before ovulation, other regress
During transition (60d) LH upregulated= takes 2-3 non-ovulatory cycles before sufficient LH for ovulation
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Who to TX
why is the mare not cycling?
consider-time of year, what are the rest of mares doing?
Previous Hx- e.g. always has had trouble?
Ensure no underlying problems
Do you Tx pregnant mares?
A. Change Photoperiod
Extra light (16hrs light, 8hrs dark)= first ovulation after 60-80d of tx
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Equilume
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Advance breeding season, BUT reduce gestation
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D. Dopamine antagonists
E.g. Doperidone, Sulpiride, Reserpine
Increase prolactin, stimulate follicular activity (stimulate expression of Gn receptors)
Light, warmth, progression in transition necessary for drug action
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E. Prog
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Mare in oestrus, has follicles >20mm, serum prog >2 ng/mL
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- Synchronisation of Oestrus
not commonly successful- problem in getting precise synchrony (long oestrus, variable ovulation)
A. PG
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Use
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Side Effects= sweat, colic
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E.g. Cloprostenol, dinoprost, luprostiol
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B. Prog.
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Oestrus 3-5d later, ovulate in that oestrus (ie 10d after Tx)
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Equity
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2 injections a mnth apart, ovaries decrease follicular activity 6wks after 1st
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- Control timing of ovulation
Need follicle to be large and mature enough- soft, >35mm, evidence of oestrogen (e.g. tease, US follicle and endometrial folds), mucosa pink, moist
Times Ovulation
hCG (Chorulon): mare well developed follicle, oculate in 24-48hrs
Deslorelin (GnRH agonist implant-Ovuplant, or injectable- Biorelease Deslorelin) give when large follicle= ovulate in 36-48hrs
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E.g. Equine FSH 12.5mg IM BID when follicle mid-sized. until largest follicle >35mm, PG on second day of Tx.
5-30d= PG, single injection= luteolysis= return to oestrus within 1wk
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>35d= endometrial cups and accessory CL= multiple PG injections, may not return to oestrus until cups regress
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Saline infusion: may use together with PG, can add AB
Mid-Late preg
Drugs
PGE to external cervical os to dilate, 2-4 hrs later PGF injection= 1 hr later 5-10 IU oxytocin IV/IM every 30 mins until foetus expelled
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When
Mature foals (better survival) if immmature= resp difficulties, non-ossified bones
Signs of parturition NOT ACCURATE in mares e.g. waxing, relaxation etc
Atleast 330d gestation, colostrum in udder, relaxed cervix, pelvic lig. relaxation.
Assess maturity via mineral changes in colostrum (e.g. Ca >40 mg/dL- 200mmol/L, Na/K ration in mulk- more K)
Drugs
Oxytocin
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Examine often for signs of placental separation, removal foal if this occurs
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PG
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Dinoprost= assoc with preature placental separation, dystocia and dead foals- use other PGF anologues
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Corticosteroids
Physiology of partution different- exogenous corticosteroids dont reliably induce parturition (vs ruminants)
BUT still TAKE CARE
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may not pass placenta of mare; induction of foetal maturity may req intrafoetal injections of glucocorticoids/ ACTH
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Prog= in late preg sufficiennt from placenta= ovariectomy doesnt interfere (horse, sheep, cat)
vs needs CL: goat, pig, cow, dog, alpaca
