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Heifers (n = 500) were fed 0.5 mg/ day of melengestrol acetate for 14 days, and 19 days later, administered PGF2α. Following PGF2α, heifers were detected for estrus and artificially inseminated (AI) approximately 18-24 hours later. Three days following PGF2α, heifers not detected in estrus were given GnRH and AI. Heifers were AI with one of two sires, either conventional or sexed semen, creating four possibilities for AI sire. Pregnancy rate was greater for conventional than sexed semen. In addition, more heifers detected in estrus were pregnant than heifers time AI. Further research is needed to establish the optimum estrus synchronization program with sexed semen.