Freezing technology of bull sperm in relation to its survivability and fertilization ability

Fertility is one of the most important production trait, which significantly affects the economy of cattle breeding, but its level is currently insifficient. Generally, the fertility has low heritability, is influenced by many genetical and environmental factors. Bull fertility is represented by initial fresh semen quality followed by quality of produced insemination doses subsequently used for artificial insemination. Artificial insemination is biotechnological method nowadays the most worldwidely applied. The procedure of processing fresh semen and subsequent cryopreservation causes damage of the important parts of spermatozoa, loss of their fertilization ability or directly cell dead. Therefore the effort to ensure the highest fertilization ability during the process of production insemination doses includes optimalization of fresh semen processing, its dilution, dosage packing, cooling, equilibration, freezing, and thawing. Currently, the addition of LDL (low-density lipoprotein) into the commercially produced diluents for bull semen is positively evaluated. LDL has excellent properties for spermatozoa membrane preservation, but its optimal concentration is not clearly defined yet. Also combination of optimal equilibration and freezing process is very important for semen processing. Recommended length of equilibration is more than 2 hours in the cooling box, followed by computer controlled freezing of insemination doses allowed precise control of ice crystals formation. Therefore the aim of this work is to optimize these processes which contribute to maintaining of spermatozoa viability after thawing and can ensure higher level of conception rate of dairy cows subsequently resulting in improving the economic efficiency of their breeding