Evaluation of llama sperm chromatin preserved using different methods of conservation

Abstract

South American camelids are internationally valued for their high quality fibre and their low cholesterol content meat. Thus, applying biotechnology in genetically superior animals would allow populations to be improved. Alternative methods of semen preservation such as desiccation and dehydration, which are easy to prepare and store and have a low cost, have been used in other species. These techniques have been used in our laboratory to preserve llama semen and two methods that evaluate sperm chromatin alterations have been developed: the Toluidin Blue stain and the Sperm Chromatin Dispersion technique. Additionally we have studied the effect different preservation processes have on llama sperm chromatin. We have observed an increase in chromatin decondensation in cooled semen when compared to the raw semen sample. When deep freezing semen, we have assayed two different cryoprotectors: glycerol (G) and dimethylformamide (DMF), both in a concentration of 7%; and two different stabilization temperatures: room temperature and 5º C. We observed that semen that was stabilized at 5º C and all freezing protocols showed a significantly higher number of sperm with chromatin condensation alterations, except semen frozen in Lactose-Egg yolk-Glicerol (LY-G) and stabilized at room temperature, which was not significantly different from raw semen. The processes of desiccation and dehydration do not alter chromatin condensation in semen preserved for a short time (up to 21 days). Nevertheless, increases in decondensation and a high level of sperm chromatin fragmentation were observed in desiccated and dehydrated samples when they were preserved for 2 and 4 months. The work carried out allowed evaluation of the effect different conservation methods have on the DNA of llama spermatozoa.