Cryopreservation of bull semen in OptiXcell® and conventional extenders: Comparison of semen quality and fertility

Commercially available OptiXcell (R) extender was compared with conventional extenders for freezability and in vivo fertility of bull semen. Semen was collected from three Friesian bulls for five weeks (replicate) and qualifying ejaculates (motility >60%, concentration >0.5 billion/mL, volume > 1mL) were diluted (37 degrees C; 50 x 10(6) spermatozoa/ml) with OptiXcell (R), tris-citric egg yolk and egg yolk-citrate extenders. Diluted semen was cooled to 4 degrees C in 2 hours, equilibrated for 4 hours and filled in 0.5 ml straws. The straws were kept over liquid nitrogen vapours for 10 minutes and plunged into liquid nitrogen. Percentages of post thaw sperm motility and plasma membrane integrity were recorded higher (P< 0.05) in OptiXcell (R) compared to tris-citric egg yolk followed by egg yolk-citrate extender. Sperm viability (%) were recorded higher (P<0.05) in OptiXcell (R) compared to tris-citric egg yolk and egg yolk citrate extender. Percentages of normal apical ridge and DNA integrity were higher (P<0.05) in OptiXcell (R) and tris-citric egg yolk extender compared to egg yolk-citrate extender. Higher (P<0.05) fertility rate was recorded with semen frozen in OptiXcell (R) compared to triscitric egg yolk and egg yolk-citrate extender. In conclusion, OptiXcell (R) is superior to conventional extenders for spermatozoal quality of frozen-thawed bull semen and produced higher fertility rates under field conditions.