Flumethasone delays or prevents estrus in ovariectomized and intact heifers given Syncro-Mate B ®

Abstract

This study was conducted to determine if a glucocorticoid (flumethasone) affects the expression of behavioral estrus in heifers given Syncro-Mate B (SMB). Ten ovariectomized heifers and 10 intact cyclic heifers were given the SMB treatment. The ovariectomized heifer trial was replicated 4 times and the intact heifer trial twice. The SMB treatment involved giving an injection containing 3 mg norgestomet and 5 mg estradiol valerate (EV). An implant containing 6 mg norgestomet was placed subcutaneously under the outer surface of one ear at the time of injection and was removed 9 d later. At the time of implant removal, half of the heifers in each replicate were given 5 mg of flumethasone. Heifers were checked for estrus, and blood was collected and measured for estradiol-17β (E 2) concentration every 8 h for 72 h after implant removal. Flumethasone reduced (P = 0.06) the number of intact (100 versus 70%) and ovariectomized heifers (65 versus 35%) that exhibited estrus. Heifers that exhibited estrus after treatment with flumethasone did so later than controls in both the intact (42 ± 3 h versus 36 ± 2 h; P = 0.11) and the ovariectomized (53 ± 3 versus 40 ± 2%; P < 0.005) groups. Flumethasone did not alter mean concentrations of E 2 in intact or ovariectomized heifers. Apparently, flumethasone suppresses or delays the expression of estrus in most treated heifers. However, the effect is not caused by mechanisms at the ovarian level or by decreased concentrations of E 2 in the serum.