The spermatozoon is a specialised cell, designed to penetrate into the ovocite and to fertilize it. For this purpose it uses different mechanisms, as the hyperactive movement and the enzyme release to break ovocite membranes. These enzymes, acrosine and hialuronidase, are located into the acrosome, cellular structure that covers the sperm head like a “cap”.

The acrosome is a big vacuole adapted to sperm head top and it is covered by the sperm plasma membrane. Therefore, in order to release its contents a membrane fusion process must be developed between  both acrosome and plasma membranes. The release of the acrosome enzymes (acrosome reaction) must take place just in the right moment because this process cannot be reversed and if it is developed earlier (early acrosome reaction) the sperm would lose its penetration ability and thus the possibility of fertilization. In order to control this hazard, the sperm is to previosly undergo a through the capacitation process, consisting on some changes at the plasma membrane level that allows the acrosome reaction tocommence.

This event secuence is to take place near the ovocite at a very precise momnet. to regulate it, female genital tract owns various  mechanisms able to put back and forth the entire process Furthermore, seminal plasma contains a decapacitation factor, acrosome presevative, wich is diluted gradually during the sperm transport through the female genital tract.

The acrosome is there are several external factors that can induce an early acrosome reaction that must be avoided, as sudden  and the presence of calcium  or bicarbonate ions in specific concentrations in the external medium. For these reasons, the process of boar semen preservation at 15ºC must be developed under stable temperature conditions and using a preservation medium with a chemical composition that avoids the hazards mentioned above.