The efficiency of superovulating mares with an enriched fraction of eq
uine follicle-stimulating hormone (feFSH) and an equine pituitary extr
act (EPE) with similar FSH content but differing in the LH amount was
compared. Mares were randomly assigned to an feFSH (n=5) or EPE (n=5)
treatment. The experimental period was of 2 successive estrous cycles,
with the first cycle as the control. At Days 6 and 7 of the estrous c
ycle, the mares received 250 mu g im cloprostenol. The treatments cons
isted of daily injections of 25 mg feFSH or EPE beginning on Day 6 pos
t ovulation. Mares were inseminated every other day until the last ovu
lation was detected. When the mares in the control and treatment cycle
s developed at least I or 2 greater than or equal to 35-mm follicle, r
espectively, the treatment was interrupted, and a single injection of
EPE (25 mg, iv) was administered to induce ovulation(s). Nonsurgical e
mbryo recovery was performed 6 or 7 d after ovulation in both control
and treatment cycles. The number of ovulations per mare was not signif
icantly different (P>0.05) between feFSH and EPE groups, but both were
higher (P<0.05) than that of the control cycle. The number of recover
ed embryos per ovulation was similar (P>0.05) for control, feFSH and E
PE groups. The high amount of LH presented in EPE did not affect the s
uperovulatory response of the mares. Superovulatory treatments increas
ed the ovulation rate of mares but did not affect the embryo recovery
rate per ovulation. (C) 1998 by Elsevier Science Inc.