The objective of this study was to evaluate the suppressive effect of an LHRH antagonist, Cetrorelix @entity31806 ( @entity31806 ), on secretion of LH, FSH and ovarian function in beef heifers. In Exp. 1, heifers were treated with a single dose of 10 microg/kg body weight intramuscularly on d 3 of the estrous cycle. In Exp. 2, heifers received either a single injection (100 microg/kg) of @entity31806 on d 3 of the estrous cycle or multiple injections of 20 microg/kg on d 3, 4, 5, 6, and 7. Serum LH, but not FSH, was suppressed from one to several days. However, neither FSH nor @entity1420 was significantly altered. In Exp. 3, heifers received an injection vehicle (5% @entity2656 ) or 100 microg/kg BW of @entity31806 on d 1 of the estrous cycle (30 h after first observed standing estrus). Injection of @entity31806 suppressed LH pulse frequency on d 3, 5, and 7 (P < 0.001). The mean LH concentrations in the @entity31806 treatment groups were lower on d 3 (P < 0.01) and 5 (P < 0.05). There were no differences (P > 0.1) between the two groups in the mean concentrations of LH on d 1, 7, or 14. Treatment did not affect the secretion pattern or concentration of FSH. Injection of @entity31806 did not alter @entity53 -173 concentrations (P > 0.1). Treatment reduced corpus luteum (CL) function as indicated by lower @entity1420 production. However, the length of the estrous cycle was not shortened. These data show that the CL can form and survive in the face of depressed LH concentrations during the early stages of the estrous cycle.

LHRH antagonist decreases LH and XXXX secretion but does not alter length of estrous cycle in heifers.

@entity2656 :: ('MESH:D008353', 'Chemical') :: ['mannitol'] @entity31806 :: ('MESH:C062876', 'Chemical') :: ['SB-75'] @entity1420 :: ('MESH:D011374', 'Chemical') :: ['progesterone'] @entity53 :: ('MESH:D004958', 'Chemical') :: ['estradiol']
@entity1420 :: (MESH:D011374,Chemical) :: ['progesterone']
