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ABSTRACT. Silenciato L.N., Mello M.R.B., Andrade R.B., Daflon Júnior F.C., Rodrigues Neto J.B., Cavalcante M.C. & Palhano H.B. [Efficiency of two FTAI protocols in crossbred dairy cows during different seasons.] Eficiência de dois protocolos de IATF em vacas leiteiras mestiças em diferentes estações do ano. Revista Brasileira de Medicina Veterinária. 38(Supl.2):169-174, 2016. Departamento de Reprodução e Avaliação Animal, Instituto de Zootecnia. Universidade Federal Rural do Rio de Janeiro, Rodovia BR 465, Km 7, Seropédica, RJ 23890-000, Brasil. E-mail: email@example.com This study evaluated the conception and pregnancy rates of crossbred dairy cows submitted to two FTAI protocols in different seasons. Ninety-five multiparous cows were randomly allocated into two treatments: Group I - GnRH + intravaginal P4 device at D0; prostaglandin and withdrawing the device at D8; GnRH + FTAI at D10. For Group II, the protocol employed was similar to GI but without P4 device. The groups were evaluated during rainy (October to April) and dry season (May to September). Conception (CR) and pregnancy rates (PR) in Groups I and II during the rainy season were, respectively, 40% and 68% (Group I) and 8% and 16% (group II) with a significant difference (p <0.05) between groups. The values of CR and PR for groups I and II, in the dry season, were 28% and 44% (Group I) and 10% and 20% (Group II), respectively, without significant difference (p> 0.05). When conception and pregnancy rates were compared between the rainy and dry season within each group, there was no statistical difference. It is concluded that the season did not affect the FTAI efficiency and that the inclusion of progesterone in the protocol improved conception and pregnancy rates during the rainy season.