Progesterone-based fixed-time artificial insemination protocols for dairy cows: Gonadotropin-releasing hormone versus estradiol benzoate at initiation and estradiol cypionate versus estradiol benzoate at the end - Melo, Leonardo de França e; Monteiro Junior, Pedro Leopoldo Jerônimo; Surjus, R. S; Drum, Jéssica Nora; Wiltbank, M.C.; Sartori, Roberto (Journal of Dairy Science, 2016)