Efficiency of using a combination of mono- and disaccharides in a diluent for freezing rooster semen

Different combination of saccharides can provide better semen protection during freezing/thawing cycle. Until now, the disaccharide maltose has not been used as a component of the medium for cryopreservation roosters’ semen. Since maltose is not involved in carbohydrate metabolism of spermatozoa, there is an assumption about its role in strengthening the structure of the glycocalyx, which is a progressive evolutionary cellular structure that regulates specific cellular adaptations to a certain temperature, chemical and other paratypical effects. In this work, in order to increase the fertility of frozen/thawed semen, we tested a combination of saccharides in the diluent for cryopreservation of roosters’ semen. For the first time, maltose has been proven to be effective in combination with fructose in a diluent to increase the fertility of frozen/thawed roosters’ semen. The aim of the study was to determine the optimal concentration of the test component of maltose based on the diluent of the Leningrad Cryoprotective Medium (LCM) (1984) for freezing the semen of roosters and determining the time of maintaining the functional usefulness of frozen/thawed cock semen in the genital tract of the hen. The experiment was carried out in the Center for Collective Use Genetic collection of rare and endangered chicken breeds (the Russian Research Institute of Farm Animal Genetics and Breeding, 2020) on a breed of Russian white chickens (♂ n = 10, ♀ n = 30) at the age of 46-50 weeks. Three variants of media for cryopreservation of roosters’ semen with different ratios of saccharides were evaluated. In each group, the Mal-10 (fructose 0.72 %, maltose 0.166 %), Mal-20 (fructose 0.64 %, maltose 0.326 %) and LCS-control (fructose 0.8 %, maltose 0 %), there were 10 hens for insemination. The results show not only an increase in the total percentage of fertilized eggs when using frozen/thawed semen in the Mal-10 (92.6 %) and Mal-20 (86.3 %) groups compared to the LKS-control group (74.7 %), but also an increase in the duration of the functional usefulness of spermatozoa in the genital tract of hen within 5 days at the level of native sperm. Counting the points of interaction of spermatozoa with the perivitelline membrane of the yolk 5 days after the last insemination showed that the functional ability of spermatozoa is much higher when using experimental media containing maltose, 67.0 pcs/cm2 for Mal-10 and 110.7 pcs/cm2 for Mal-20 vs. 40.1 pcs/cm2 in maltose-free LKS-control. The longest duration of the functional usefulness of spermatozoa was noted in the Mal-20 group. Even on day 15 after the last insemination, the fertilization capacity of frozen/thawed semen was recorded at the level of 20 %. A regression equation was drawn up for the relationship of egg fertilization with the points of interaction of spermatozoa with the perivitelline membrane of the yolk. To obtain an egg fertilization level of ≥ 80 %, the functional usefulness of frozen-thawed spermatozoa (expressed through the number of points of interaction with the perivitelline membrane of the yolk) should be ≥ 60 pcs/cm2. This was achieved by using an experimental diluent with 0.326 % maltose. The results obtained open up the possibility of using cryopreserved semen not only in preserving the gene pool, but also in breeding programs.