Effect of cryopreservation on biological parameters of semen in Romanov breed x argali hybrid rams

Cryopreservation of genetic material and artificial insemination is an important element of assisted reproductive technologies. Establishing cryobanks of biomaterial, derived of high-valuable breeding rams, provides the production of the maximal number of offspring. This technology allows more effectively use the genetic material with higher efficiency, save and restore the populations of rare and endangered species and carry out crossbreeding and hybridization between isolated populations. The most common biomaterials are the sperm, which are used in the programs for the conservation and restoration of wild and domestic genetic resources. This is associated with the availability and easiness of producing sperm. In sheep breeding, the use of reproductive technology has the local character in contrast to other livestock industries. One reason for this is the low efficiency of application of frozen-thawed ram semen that is caused by some complexities involved in sperm cryopreservation of this animal species. During the freezing and thawing process, the sperm undergoes significant technological impact. Some stages of this process are the shock to semen and lead to the destruction of a large part of cells or to the damaging their individual organelles or segments. Less is known about the freezing capacity of sperm derived from hybrid rams, which are produced by hybridization of domestic and wild Ovis species. Taking this into account the aim of our research was to study the effect of freezing and thawing process on the biological parameters of sperm derived from purebred Romanov ram and hybrid rams carrying argali ( Ovis ammon ) blood. As a material for our research, we used the sperm of hybrid rams of different origin: F1 ( n = 1, 50 % argali, produced by surgical insemination of Romanov ewe with frozen-thawed sperm of argali ram); BC1 ( n = 5, 25 % argali blood, produced by backcrossing of Romanov ewes with F1 ram); BC2 ( n = 5, 12.5 % of argali blood, produced by backcrossing of Romanov ewes with BC1 rams). The sperm of purebred Romanov ram (RAM) was used as a control. Qualitative and quantitative parameters of freshly derived and frozen semen of the experimental animals, the percentage of motile and immobile spermatozoa, their cryoresistance, the state of the acrosome and the degree of chromatin condensation were studied. The motility of spermatozoa was decreased significantly in sperm of both of hybrid and purebred rams (by 47 and 50 %, respectively). The cryoresistance of spermatozoa of F1 hybrid ram was increased by 9 %, the osmotic resistance increased - by 20 % and dehydrogenase activity - by 44.5 % comparing to purebred Romanov ram. With the decrease of blood ratio of wild species, the decrease in differences for above-mentioned parameters was observed: the differences between BC2 and ROM were 2.2, 4.7 and 10.0 %, respectively.