'Semen dilution effect' on sperm variables and conception rate in buffalo.

The study aim was to determine how to minimize effects of buffalo semen dilution by evaluating the use of egg yolk (EY), low-density lipoprotein (LDL), and OptiXcell (OC) extenders. Ejaculates (n = 18 from six bulls) were divided into three aliquots that were diluted separately with EY, LDL, and OC extenders corresponding to 20 million (M), 12 M, and 2 M sperm/dose, respectively, and cryopreserved. There were a lesser sperm motility, plasma membrane integrity, and percentage un-capacitated sperm with the 2 M sperm/dose, however, the LDL extender was more effective than OC and EY extender for cryopreservation of buffalo sperm. Excess semen dilution resulted in sustained sperm velocities (curvilinear velocity, average path velocity, and straight linear velocity), and these were greater with use of the OC than LDL and EY extenders. There was no change in amplitude of sperm lateral head displacement (ALH) with respect to dilution, but with regard to extender effects, ALH was greater in sperm extended in LDL and OC than EY. Semen dilution to 2 M sperm/dose resulted in a greater mitochondrial superoxide production. Conception rate (CR) was unaffected with 20 and 12, however, with the 2 M sperm/dose dilutions there was a lesser CR. In conclusion, buffalo semen dilution to the extent of 12 M sperm/dose did not affect most of the seminal variables and CR. Using LDL extender at 2 M sperm/dose protected sperm from the 'semen dilution effect' to a greater extent than with use of EY and OC extenders.