Effects of supplementation of tris-egg yolk extender with different sugars and antioxidants on freezability of ram semen

This study was designed to determine the effects of the combined addition of different levels of certain sugars (trehalose, sucrose and raffinose) and antioxidants (vitamin E, C and taurine), in Tris-egg yolk extender on frozen-thawed ram semen parameters. Semen samples were collected from five healthy, mature and fertile Iranian Afshari rams, twice a week for 8 weeks. Selected samples were pooled and diluted with a Tris-egg yolk extender containing different levels of sugars and antioxidants. In Experiment 1, different levels of trehalose (0, 50 and 100 mM) were tested with different levels of taurine (0, 25 and 50 mM), vitamin E and C (0, 1 and 2 mM). In Experiment 2, different levels of sucrose (0, 60 and 80 mM) were tested with different levels of taurine (0, 25 and 50 mM), vitamin E and C (0, 1 and 2 mM). In Experiment 3, different levels of raffinose (0, 5, 10 mM) were tested with different levels of taurine (0, 25 and 50 mM), and vitamin E and C (0, 1 and 2 mM). In Experiment 4, the selected extenders of experiments 1, 2 and 3 were compared statistically with control (no selected sugar and antioxidant) extender. The results of experiments 1, 2 and 3 revealed that the highest frozen-thawed sperm parameters were recorded for the selected extenders containing 100 mM trehalose +2 mM vitamin E (T100E2), 60 mM sucrose + 2 mM vitamin E (S60E2) and 10 mM raffinose + 2 mM vitamin E (R10E2), respectively. The results of experiment 4 revealed that the post-thaw sperm total motility in T100E2 (62.41 +/- 2.41%), S60E2 (59.52 +/- 1.91%) and R10E2 (58.33 +/- 2.00%) was higher than that of the control extender (46.00 +/- 1.79%; P < 0.05). Similarly, the progressive sperm motility in T100E2 (57.18 +/- 1.96%), S60E2 (57.49 +/- 1.94%) and R10E2 (55.03 +/- 2.99%) was also higher than that of the control extender (41.20 +/- 1.70%; P < 0.05). Post-thaw sperm viability in selected extenders of T100E2 (65.20 +/- 2.67%), S60E2 (62.00 +/- 2.07%) and R10E2 (61.80 +/- 2.46%) was higher than that of control extender (51.00 +/- 1.88%; P < 0.05). In conclusion, the addition of 100 mM trehalose, 60 mM sucrose and 10 mM raffinose combined with 2 mM vitamin E in Tris-egg yolk extender significantly improved frozen-thawed ram semen parameters.