**12. Use of FT semen in porcine AI**

Contrary to what occurs in cattle, where FT semen is routinely used for AI [81], cryopre‐ served boar semen is used in less than 1% of the AIs performed around the world. The rea‐ sons behind this restricted use of FT boar semen are the low survivability of sperm after the freeze-thawing process and the shorter lifespan of the surviving sperm. These result in low‐ er FR and small LS compared with AI using semen preserved in liquid form [48]. Further‐ more, owing to the restricted lifespan of the FT boar sperm, excessive sperm numbers are used often 5 to 6 x109 sperm per dose. Moreover, at least two AIs are usually performed per estrus in order to reach acceptable fertility rates in the field [82]. Altogether, few doses can be obtained from a single ejaculate and too many sperm are used to ensure fertilization. A decrease in the number of sperm per dose is therefore required to improve the use of ejacu‐ lates, so that the production will be cheaper and the use of genetically superior sires more effective.
