Association between the presence of protein bands in ram seminal plasma and sperm tolerance to freezing

This study evaluated associations between the presence of protein bands in ram seminal plasma and the quality of sperm frozen with distinct extenders. Ejaculates were frozen in a Tris–egg yolk based extender, including either 5% glycerol or 100 mM trehalose. Seminal plasma samples were submitted to unidimensional electrophoresis. Pre-freezing and post-thawing sperm quality was similar between extenders (P > 0.05). A total of 26 bands were identified in ram seminal plasma. Pre-freezing sperm motility was increased when the 15, 19 and 80 kDa bands were present in seminal plasma (P < 0.05). The presence of an 11 kDa band in seminal plasma was associated with reduced pre-freezing membrane integrity (P < 0.05). After thawing, both sperm motility and membrane integrity were reduced when a 24 kDa band was present in seminal plasma (P < 0.05). Post-thawing acrosome integrity was greater in the presence of a 31 kDa band in seminal plasma (P < 0.05). Regardless of the cryoprotectant included in the freezing extender, these six bands may be potential markers for ram sperm tolerance to freezing.