Semen extender is a liquid diluent which is added to 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.

Function

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

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, DMSO

Dimethyl sulfoxide

Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...

 and dimethylformamide

Dimethylformamide

Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...

. Egg yolk, which has cryoprotective properties, is also a common component.

Ingredients

In the equine, Kenney extender (named after its developer, Dr. Robert M. Kenney of the University of Pennsylvania, New Bolton

New Bolton Center

The University of Pennsylvania School of Veterinary Medicine’s 700 acre New Bolton Center campus in Kennett Square, Pennsylvania, is home to one of the busiest large animal teaching veterinary clinics in the nation. Founded in 1964 with contributions from equestrienne Esther du Pont Thouron and...

) has been used for many years, and contains a non-fat dried milk solid (NFDMS) and glucose

Glucose

Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

. Dual-sugar extenders typically have similar ingredients, with an additional sugar, sucrose

Sucrose

Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...

. 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

Ticarcillin

Ticarcillin is a carboxypenicillin. It is almost invariably sold and used in combination with clavulanate as Timentin. Because it is a penicillin, it also falls within the larger class of beta-lactam antibiotics. Its main clinical use is as an injectable antibiotic for the treatment of...

 (often used in combination with clavulanic acid

Clavulanic acid

Clavulanic acid is a competitive β-lactamase inhibitor combined with penicillin group antibiotics to overcome certain types of antibiotic resistance. It is used to overcome resistance in bacteria that secrete β-lactamase, which otherwise inactivates most penicillins...

 under the designation timentin), amikacin sulfate, penicillin

Penicillin

Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

, and gentamicin

Gentamicin

Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila...

 are commonly used. The latter - gentamicin - has been noted to reduce sperm motility in the equine.

Porcine

• Beltsville Liquid (BL-1)
• Acromax
• Beltsville Thawing Solution (BTS)
• Illinois Variable Temperature (IVT)
• Modena
• Kiev
• MULBERRY III
• Reading
• X-Cell
• Zorlesco
• ZORPVA
• DURAGEN
• Androhep EnduraGuard TM Minitube of America
• Androhep Plus Minitube of America
• Androstar Plus Minitube of America
• M III Minitube of America
• BTS Minitube of America

Bovine

• Bioxcell
• CRYOBOS
• Andromed CSS Minitube of America
• Triladyl Minitube of America
• Biladyl Minitube of America

Equine

• Kenney (often marketed under a brand name - e.g. E-Z Mixin')
• VMDZ
• INRA '96
• Universal dual-sugar
• AndroMed-E Minitube of America
• Gent Extenders Minitube of America
• Equipro Minitube of America
• Spervital extenders (http://www.spervital.nl)