The effect of different concentrations of glycerol and lecithin on the characteristics of Iranian Holstein bull sperm in repeated freezing and thawing conditions

Different compounds such as soy lecithin have been used in the sperm freezing of different species. Repeated freezing was less considered in farm animals and doing this proccess could be valuable for the rare breeds. Inorder to investigate the effect of lecithin and glycerol on sperm quality in repeated freezing and thawing, frozen bull sperm straws were thawed and the previous diluent eleminated. Then, the sperms were diluted in Tris buffer freezing extender containing different concentrations of glycerol (3, 5 and 7%) and soya lecithin (1% and 2%) and were frozen again. After two weeks, the sperms were thawed and sperm characteristics were evaluated immediately after thawing and up to two hours incubation at 40 °C. The results indicated that treatments containing 5% glycerol with one percentage lecithin (G5L1) and 3% glycerol with 2% lecithin (G3L2) had the highest and the lowest percentage of motility, viability and membrane integrity of sperm, immediately after thawing and one hour incubation at 40 °C respectively. The percentage of motile and viable sperms in G5L1 treatment was significantly higher (P <0.05) than the control group after 2 hours of incubation at 40 °C but sperm membrane integrity did not have significant difference with the control group (P>0.05). In general, the results showed that using 5% glycerol with 1% can improve the sperm characteristics in repeated freezing and thawing.