In normal conditions, boar semen has a slightly alkaline pH (7.3-7.9). However, if it is not properly diluted, becomes more acid progressively. As a norm of handling and correct use of semen, it is desirable that the ejaculate spends as little time as possible at 37ºC since at this temperature sperm cells are stimulated to move and accumulate lactic acid.
A very noticeable feature of boar sperm cells is the abundance of phospholipids in the plasma and acrosome membranes. This biochemical characteristic determines that these membranes are particularly vulnerable to lipidperoxidation, this causes damages to sperm cell and later leads to a loss of metabolites and enzymes, essential for its functionality and ability to fertilize the ovum.
All extenders chelating agents whose job is to capture ions that could accelerate deterioration reactions in the sperm cell, maintaining therefore cell integrity for long periods. The most detrimental ions are which acts as a catalyst of lipid peroxidation, Pb2+ and Cu2+ which cause chemically-originated aglutination of sperm, and Ca2+ which can initiate the acrosome reaction. This reaction is essential at the exact moment of fertilization and would be premature and detrimental if it were to occur during the preservation of semen.