The use of butylated hydroxytoluene in cryopreservation of boar semen
The objective of the study was to determine the effect of butylated hydroxytoluene (BHT) on the quality and fertilizing capacity of frozen-thawed (FT) boar semen. Semen from five boars (36 ejaculates) was resuspended in lactose-egg yolk-glycerol extender supplemented with 0 (control), 1.0 (R1), 1.5 (R2) or 2.0 mM BHT (R3). Sperm quality was assessed based on motility (CASA; TM: total motility; PM: progressive motility), phosphatidylserine (PS) translocation across the plasma membrane (Annexin-V-FLuos Staining Kit) and DNA fragmentation (TUNEL Assay). The FT semen was also used for intrauterine artificial insemination (AI) of synchronized gilts. The fertilizing capacity of the FT semen was assessed on the basis of the gilt insemination rate and the number of morphologically normal embryos. The quality of the preimplantation embryos was determined by observing a TUNEL-positive reaction. The highest percentage of progressive motile and viable spermatozoa was noted in extender R3 (74.8 ±4.4% and 63.7 ±5.8%), as compared with the control (38.3 ±2.8% and 36.1 ±2.6%). The addition of BHT to the extender did not increase early apoptotic changes in the frozen-thawed spermatozoa with respect to the control. Irrespective of the variant of the extender, cryopreservation and thawing did not induce fragmentation in the boar spermatozoa. The highest number of morphologically normal embryos from inseminated gilts was observed in the case of semen cryopreserved in extender supplemented with 1.5 mM BHT. No significant differences were observed in DNA fragmentation in the expanded blastocysts from gilts inseminated with FT semen cryopreserved in the extenders analysed.