Positive and negative effects of progesterone during timed AI protocols in lactating dairy cattle - Wiltbank, M. C; Souza, A. H; Giordano, J. O; Nascimento, A. B; Pereira, M. H. C; Fricke, P. M; Surjus, R. S; Zinsly, F. C. S; Carvalho, P. D; Bender, R. W; Sartori Filho, Roberto (Animal Reproduction, 2012)