Effects of XXXX implants in @entity1641 : single implants in stallions and steroid-treated geldings and multiple implants in mares.

@entity43 @entity1641 @entity1420 @entity53 @entity194 @entity1176 @entity27404
Three experiments were performed to test the following hypotheses: 1) stallions and/or @entity1420 - @entity53 -treated geldings could serve as models for the effects of a single implant of the @entity1176 analog, @entity27404 , on LH and FSH secretion by mares; and 2) multiple implants of @entity27404 could be used as a means of inducing @entity43 in mares for future study of the mechanisms involved in the @entity194 observed in some mares after a single implant. In Exp. 1, nine light @entity1641 stallions received either a single deslorelin implant (n = 5) or a sham injection (n = 4) on d 0. In Exp. 2, 12 geldings received daily injections of @entity1420 on d -20 through -4, followed by twice-daily injections of @entity53 on d -2 to 0. On the morning of d 0, geldings received either a single deslorelin implant (n = 6) or a sham injection (n = 6). Daily injections of @entity1420 were resumed on d 2 through 15. In Exp. 1, plasma LH and FSH were elevated (P < 0.05) in the treatment group relative to controls at 4, 8, and 12 h after implant insertion. In the treated stallions, FSH was decreased (P < 0.05) on d 3 to 13, and LH was decreased on d 6 to 13. In Exp. 2, plasma LH and FSH were elevated (P < 0.05) at 4,8, and 12 h after deslorelin implant insertion. Plasma LH was suppressed (P < 0.05) below controls on d 2 to 7, 9, and 11 to 15; plasma FSH was suppressed (P < 0.05) on d 4 to 15. In Exp. 3, 21 mares were used to determine whether multiple doses of deslorelin would cause @entity43 . Mares received one of three treatments: 1) sham injections; 2) three implants on the first day; or 3) one implant per day for 3 d (n = 7 per group). Treatment with multiple implants increased (P < 0.05) the interovulatory interval by 14.8 d and suppressed (P < 0.01) LH and FSH concentrations for approximately 25 d; no mare exhibited @entity43 . In conclusion, after an initial short-term increase in LH and FSH secretion, deslorelin implants caused long-term suppression of both gonadotropins in stallions as well as in geldings treated with @entity1420 and @entity53 to mimic the estrous cycle. It is likely that either of these models may be useful for further study of this suppression in @entity1641 . Although multiple implants in mares suppressed gonadotropin secretion longer than a single implant, the lack of @entity43 indicates that the @entity194 observed after a single implant in previous experiments was likely due to the susceptibility of individual mares.
