One of the most common extenders used for this purpose is skim milk-egg yolk extender (SMEY). The process of frozen semen production requires an extender to maintain the quality of semen.
Success in the semen freezing process is influenced by the type of diluents as well as the dilution and freezing techniques used. The Limousin bull is one of the most popular exotic bulls for the AI program because exotic calves have a high value thus, there is an increasing demand for frozen semen of these bulls. The main task of the AI Centers is to produce good quality frozen (cryopreserved) semen from superior bulls, such as the Limousin bull. Indonesia also has several Regional AI Centers in various provinces including Aceh, North Sumatra, West Sumatra, South Sumatra, Lampung, West Java, Central Java, Yogyakarta, South Kalimantan, East Kalimantan, Southeast Sulawesi, South Sulawesi, West Nusa Tenggara, and Bali. Indonesia has two National Artificial Insemina- tion Centers (AI Centers), namely, the Singosari and Lembang AI Centers. Sperm motility, viability, membranes, DNA integrity, and concentrations of malondialdehyde (MDA) and aspartate aminotransferase (AST) enzymes were evaluated after thawing. The diluted semen was loaded into 0.25 mL mini straws, equilibrated, and frozen using a freezing machine. Semen that had >70% motile sperm and <20% sperm abnormality was divided into three tubes and diluted with skim milk-egg yolk (SMEY) using three different dilution techniques: One-step dilution (100% SMEY with 8% glycerol) at room temperature ( 20☌ until 25☌) two-step dilution (50% SMEY without glycerol at RT, stored at 5☌ and 50% SMEY with 16% glycerol after 1 h stored at 5☌) and three-step dilution (50% SMEY without glycerol at RT, stored at 5☌ and 50% SMEY with 16% glycerol added twice at 1 h and 1.5 h after being stored at 5☌). Immediately after collection, the semen was evaluated macroscopically and microscopically. With this combination of different approaches, acceptable fertility with cryopreserved boar semen can be achieved, facilitating the use of cryopreserved boar semen in routine AI programs.Semen was collected from three sexually mature Limousin bulls using an artificial vagina. Minimizing insemination-to-ovulation intervals, based either on estimated or determined ovulation, have also improved the fertility after AI with cryopreserved boar semen. With deep intrauterine insemination, the sperm dose has been decreased from 6 to 1x10(9) spermatozoa without compromising farrowing rate or litter size. However, cooling and thawing rates individually optimized for sub-standard freezing boars have substantially improved their sperm quality after cryopreservation. In general, final glycerol concentrations of 2-3% in the freezing media, cooling rates of -30 to -50 degrees C/min, and thawing rates of 1200-1800 degrees C/min resulted in the best sperm survival. catalase, vitamin E, glutathione, butylated hydroxytoluene or superoxide dismutase) to the still standard egg-yolk based cooling and freezing media for boar semen, effectively prevented this damage. The addition of antioxidants or chelating agents (e.g. Boar spermatozoa are exposed to lipid peroxidation during freezing and thawing, which causes damage to the sperm membranes and impairs energy metabolism. There is ongoing research to improve sperm survival after thawing, to limit the damage occurring to spermatozoa during freezing, and to further minimize the number of spermatozoa needed to establish a pregnancy. Although cryopreserved boar semen has been available since 1975, a major breakthrough in commercial application has not yet occurred.
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