Today, it is theoretically assumed that frozen storage of semen doses in liquid nitrogen guarantees sperm functionality indefinitely. However, there are few studies that objectively evaluate the effects of long-term storage on sperm quality parameters. In this study, we show a freezability analysis of bull semen stored for 1, 10, 25, 40 and 45 years at −196°C. Sperm viability and full sperm motility were analyzed by CASA system, and acrosome integrity was assessed with Coomassie blue staining. Our results showed that sperm viability and total sperm motility were not affected by long-term cryopreservation at −196°C. Specifically, we did not find any significant differences (p > 0.05) associated between different long-time storing analyzed; both parameters showed optimal values of sperm viability and total sperm motility (both over 60%). Additionally, the acrosomal integrity parameter was not affected, showing an optimal range (87±1.6-95±0.5%). We conclude that the sperm quality of bovine semen is not affected by longterm storage at −196°C. However, future field trials will be necessary in order to validate that both fertility and embryo viability are maintained for the times analyzed.

Artículo de publicación ISIThe nucleus of mammalian spermatozoa is mainly composed of chromatin associated with protamines: highly basic proteins (around 7 kDa). These highly basic proteins, due to their cysteine content, can participate in the generation of disulfide bond. These characteristics permit typical condensed nuclear structure in mature spermatozoa, where the DNA becomes organized in compacted units, similar to nucleosomes, but with 60 kb of DNA. This shape is ultimately assumed in the epididymal maturation, and the level of compaction is closely related to epididymal function. In the present work, we present a modified method to evaluate sperm decompaction using sodium thioglycolate (ST). Stallion sperm were exposed to different ST concentrations and were embedded in agarose as a supportive medium. With the use of agarose, it was easier to identify patterns of decompaction with ST, and, thus, the use of a permeabilizing solution was not necessary. This was due to the utilization of ST to evaluate chromatin compaction of stallion sperm physically permeabilized and embedded in agarose matrix.Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) 21120861 Fondef CONICYT D08I107

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