THE EFFECT OF LIPOSOMES COMPOSED OF PHOSPHATIDYLSERINE AND CHOLESTEROL ON FERTILITY RATES USING FROZEN-THAWED EQUINE SPERMATOZOA

The objective of this study was to determine if the addition of liposo mes composed of phosphatidylserine (PS) and cholesterol (CH) to equine sperm would improve pregnancy rates after sperm were cryopreserved. E jaculates from four stallions, collected every other day during May an d June were spit, treated with PSCH liposomes or HBS (Hepes Buffered S aline) and cryopreserved. Fifty-two mares were bred over eighty estrou s cycles with the frozen-thawed se men. The one cycle pregnancy rates of the mares inseminated with semen treated with liposomes (45%) were similar to mares inseminated with control semen (48 %; p > 0.05). Thus , at least at the levels used, PSCH liposomes added to equine sperm di d not improve pregnancy rates of mares inseminated with cryopreserved semen.