The protease inhibitor antipain has a beneficial synergistic effect with trehalose for ram semen cryopreservation.

The objective of this study was to examine the different concentrations of antipain and trehalose combination on post-thawed quality of ram semen cryopreserved in tris extender. Ejaculates were collected from four rams using the artificial vagina, pooled at 37°C and diluted with (A  Tre : antipain 0 μM and trehalose 0 mM (Control); A  Tre ; A  Tre ; A  Tre ; A  Tre ; A  Tre ; A  Tre ; A  Tre and A  Tre ). Diluted semen samples were gradually cooled down from 37 to 5°C in a cold cabinet; then, they were loaded into 0.25 ml straws, frozen and stored in liquid nitrogen. Sperm motility (CASA), viability, membrane functionality and abnormality were evaluated after thawing process. Progressive motility in extender supplemented with A  Tre , A  Tre and A  Tre significantly (p < 0.05) higher as compared to the control (A  Tre ). A  Tre (47.50 ± 0.73) provided the best maintenance of progressive motility in comparison with the control (40.50 ± 0.73). No significant differences were observed between all treated groups in terms of total motility, VAP, VSL, VCL, ALH, BCF, STR and LIN. The percentages of sperm with viable were significantly higher in extenders supplemented with A  Tre , A  Tre , A  Tre and A  Tre , compared to control. Addition of A  Tre , A  Tre and A  Tre to extenders improved the percentages of sperm abnormality, compared to the controls. A  Tre (67.84 ± 1.51) treatment provided the best maintenance of normal morphology compared to the other treatments. The supplementation with A  Tre , A  Tre and A  Tre improved the percentage of sperm membrane functionality when compared to the control (p < 0.05). Comparing these results with those of control diluents, the effects of supplementation were better except for A  Tre group. In conclusion, when combination of antipain (10 μM) and trehalose (30 and 60 mM) was added, they conferred a great cryosurvival capacity with their synergic effects during freeze-thawing process.