The sperm characteristics of Dorper, Santa Ines and undefined breed ram in the rainy and dry seasons was assessed. After collection with an artificial vagina, the semen was evaluated for volume, turbulence, motility, viability, morphology and concentration, frozen and stored in a cryogenic cylinder. After thawing kinematic sperm, plasma membrane integrity, acrosome integrity and mitochondrial activity were evaluated. Sperm vigor, total motility, progressive motility, straight line speed and larger line defects did not differ between the rainy and dry seasons, however, volume, turbulence, linearity, straightness and frequency of tail beats were lower (P<0.05 ) in the dry period, and sperm concentration and total defects showed lower values during the rainy season. Values for acrosome integrity and plasma membrane and mitochondrial membrane potential were lower (P<0.05) in the dry season. It is concluded that the wet and dry period influence sperm quality in ram raised in the Mid - North region of Brazil, with a higher sperm quality in the rainy season, thus suggesting cryopreservation for that period. Also, the better ram group regarding sperm quality, was the Santa Ines.
sheep; seminal characteristics; freezing