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Evaluation Of Three Estrous Synchronization Protocols In Beef Heifers1, R. N. Funston, R. J. Lipsey, T. W. Geary, R. P. Ansotegui

West Central Research and Extension Center, North Platte

Objectives of this study were to evaluate synchronization, conception, and pregnancy rates of heifers synchronized with melengestrol acetate (MGA)-prostaglandin F_2α (PGF_2α,), Select Synch, or Select Synch preceded by MGA (MGA-Select Synch). Heifers in the MGA-PGF_2α group (n = 209; BW = 378 kg) received MGA (0.5 mg/ d per heifer) for 14 d and PGF_2α (25 mg) 19 d later. Select Synch heifers (n = 213; BW = 374 kg) received gonadotropin- releasing hormone (GnRH; 100 μg) followed by PGF_2α (25 mg) 7 d later. The MGA-Select Synch heifers …

Extending Interval From Seventeen To Nineteen Days In The Melengestrol Acetate - Prostaglandin Estrous Synchronization Program For Heifers, G. H. Deutscher

West Central Research and Extension Center, North Platte

Two experiments were conducted to determine whether extending the interval between removal of melengestrol acetate (MGA) from feed and injection of prostaglandin F_2α (PGF) from 17 to 19 d would affect synchronization of estrus, conception, and pregnancy rates of beef heifers. In both experiments, heifers were fed MGA for 14 d, and PGF was given at either 17 or 19 d after cessation of MGA feeding. Heifers were observed for estrus and artificially inseminated for 5 d after PGF injection.

In Exp. 1, 240 yearling heifers were randomly assigned to either a 17- or a 19-d …