Semen extender is a liquid diluent added mixed with semen to preserve its fertilizing ability. The extender allows the semen to be freighted to the female, rather than requiring the male and female to be near to each other. Special freezing extender use also allows cryogenic preservation of sperm ("frozen semen"), which may be transported for use, or used on-site at a later date.
The addition of extender to semen protects the sperm against possible damage by toxic seminal plasma, as well as providing nutrients and cooling buffers if the semen is to be cooled. In the case of freezing extenders, one or more penetrating cryoprotectants will be added. Typical cryoprotectants include glycerol, DMSO and dimethylformamide. Egg yolk, which has cryoprotective properties, is also a common component.
In the equine, Kenney extender (named after its developer, Dr. Robert M. Kenney of the University of Pennsylvania, New Bolton) has been used for many years, and contains a non-fat dried milk solid (NFDMS) and glucose. Dual-sugar extenders typically have similar ingredients, with an additional sugar, sucrose. Other extenders (e.g. INRA '96) may also contain milk components.
Antibiotics are almost universal in semen extenders, especially those being used for shipping or freezing semen. Ticarcillin (often used in combination with clavulanic acid under the designation timentin), amikacin sulfate, penicillin, and gentamicin are commonly used. The latter - gentamicin - has been noted to reduce sperm motility in the equine.
- Beltsville Liquid (BL-1)
- Beltsville Thawing Solution (BTS)
- Illinois Variable Temperature (IVT)
- MULBERRY III
- Kenney (often marketed under a brand name - e.g. E-Z Mixin')
- INRA '96
- Universal dual-sugar
- Spermprep TYB
- ↑  Equine-Reproduction.com - FAQ-AI article
- ↑  Equine-Reproduction.com - Frozen Semen FAQ article
- ↑ Vera-Munoz O., Amirat-Briand L., Diaz T., Vásquez L., Schmidt E., Desherces S., Anton M., Bencharif D., Tainturier D.; (2009) Effect of semen dilution to low-sperm number per dose on motility and functionality of cryopreserved bovine spermatozoa using low-density lipoproteins (LDL) extender: Comparison to Triladyl and Bioxcell; Theriogenology 71:6; 895-900
- ↑ The Equine Research Hall of Fame - Robert M. Kenney
- ↑ Aurich C., Spergser J., (2007) Influence of bacteria and gentamicin on cooled-stored stallion spermatozoa; Theriogenology 67:5; 912-918
- ↑ "Semen extenders used in the artificial insemination of swine. A review". Spanish Journal of Agricultural Research (2003) 1 (2):17-27. http://www.engormix.com/semen_extenders_used_in_e_articles_87_POR.htm. Retrieved 2009-05-05.
- ↑ "Comparison of AndroMed, Bioxcell and Triladyl extender for cryopreservation of bull semen". http://www.forschungsportal.ch/unizh/p5601.htm. Retrieved 2009-05-05.
- ↑ 8.0 8.1 Aurich, C.; Seeber, P.; Müller-Schlösser, F. (Aug 2007). [Expression error: Missing operand for > "Comparison of different extenders with defined protein composition for storage of stallion spermatozoa at 5 degrees C"]. Reproduction in domestic animals = Zuchthygiene 42 (4): 445–448. doi:10.1111/j.1439-0531.2006.00828.x. ISSN 0936-6768. PMID 17635785.
- ↑ "The SpermPrep TYB Media". http://www.zdlinc.com/zdl_semendilution.html#TYB. Retrieved 2009-05-05.