INFLUENCE OF SOME FATTY ACIDS AND CHOLESTEROL ADDITION TO SEMEN EXTENDER ON FREEZABILITY AND IN VITRO FERTILIZING POTENTIALS OF RAM SPERMATOZOA

摘要

Cryopreservation of ram semen disrupts the membrane integrity of spermatozoa and reduces the motility and the fertilizing potential. The transbilayer dynamics of lipids in the plasma membrane of mammalian sperm cells is crucial for the fertilization process. The aim of the present study is to develop a treatment supporting the membrane integrity of ram spermatzoa during Cryopreservation. Semen samples were collected from six rams aged 2-3 years, pooled together and extended in Tris based extender supplemented with different'fatty acids and cholesterol concentrations. Extended semen was cooled and freezed. Percentages of motility after dilution, post - thawing and acrosomal defects as well as viability index were subjectively assessed. Frozen - thawed ram semen treated with low or high concentrations of fatty acids and cholesterol were used to assess their in vitro fertilizing potential. Addition of 1 mg/ml palmitic acid or 5 mg/ml linoleic acid significantly increased (P<0.001) post-thawing sperm motility (64.00 and 56.00%, respectively), viability indices (188.00 and 154.00, respectively), decreased acrosomal defect (15.00 and 18.00 %, respectively), enhanced significantly (P<0.05) in vitro fertilization rate (53.84- and 51.72 %, respectively) and in vitro blastocyst production (18.75 and 16.66%, respectively). On the other hand, addition of cholesterol to the diluted ram semen, even in low concentration, resulted in a drastic decrease in the post - thawing motility (40.00 %), viability index (96.00), increased acrosomal defect (27.00%) and inhibited severely in vitro blastocyst production (3.77%). In conclusion, the current results illustrated that the addition of lmg/ml palmitic or 5mg/ml linoleic acid to ram semen extender, protected ram sperm plasma membrane against cryoinjury, improved semen freezability and in vitro fertilizing potential. By contrast, cholesterol addition to the diluted ram semen drastically inhibited ram semen freezability and in vitro fertilizing potential.