Use of soy milk combined with different cryoprotectants for the ram semen cryopreservation

• The combination of soy milk and glycerol is suitable for ram semen cryopreservation.
• The combination of soy milk and dimethylformamide has no beneficial effect on freeze-thawed ram semen quality.
• Semen samples frozen with a soy milk-glycerol extender showed well embryo production rates.

The aim of this study was to determine the effect of based milk soy extender combined with two different cryoprotectants: dimethylformamide (DMF) and glycerol, on ram sperm quality after cryopreservation. Five freezing extenders were assessed: Tryladil, Andromed (controls) and three soya milk experimental extenders containing: (A) 6% glycerol, (B) 3% DMF and 3% glycerol and (C) 6% DMF. Semen samples were assessed at post dilution, prefreezing, post thawed and at 2 h after thawing. In vitro fertilization was performed with two selected extenders based on thawed semen quality. After thawing, semen samples showed a significant (P < 0.001) higher percentages of motility in presence of DMF: (B) 36.60%, (C) 41.00% vs Tryladil 28.12%, Andromed 26.32% and (A) 29.60%. However, 2 h post thawing the extenders containing DMF produced a significant (P < 0.001) negative effects on motility and acrosome integrity rates. Embryo production rates were significantly higher (P = 0.006) when fertilization was performed with semen frozen with Andromed (75.5% 8–16 cell embryos) compared to (A) (56.2% 8–16 cell embryos). In conclusion, the combination of soy milk and glycerol is suitable for ram semen cryopreservation, better than that with DMF.