Effect of sucrose, trehalose, hypotaurine, taurine, and blood serum on survival of frozen bull sperm.

Factorially arranged experiments were conducted to study the effects of adding sucrose and trehalose, known to have cryoprotective properties, blood serum, and the antioxidants taurine and hypotaurine on sperm motility after freezing and thawing at different rates. At sugar concentrations of 0.1 M, osmolality of the whole milk (WM) or egg yolk-Tris freezing medium (without glycerol) was about 370 mOsmol. Survival following freezing and thawing was reduced unless osmolality was corrected by adding pure water to reduce osmolality to about 280 mOsmol. Then the post-thaw percentages of motile sperm for control WM, and WM with 0.05 or 0.10 M sucrose, or 0.05 or 0.10 M trehalose, respectively, were 62, 55, 61, 57, and 62%. Thawing semen at 5 degrees C, versus 25 degrees C resulted in 64 versus 70% motile sperm (P < 0.05). Post-thaw survival of sperm stored at 25 degrees C for 24 h in trehalose-treated WM was superior to that in WM (P < 0.05). Hypotaurine and taurine had little effect on sperm survival. Up to 10% (v/v) of heated blood serum was generally beneficial, but gave more variable responses with different bulls. Sperm survival after cooling at -25 degrees C/min was slightly superior to that after cooling at -15 degrees C/min to -100 degrees C. The effects of the compounds studied on motility of frozen-thawed sperm were small, but if they protect sperm cell membranes, as reported for other types of membranes, they may assist sperm in surviving in the reproductive tract of the cow prior to fertilization.