AI is commercially applied worldwide to breed pigs, yielding fertility outcomes similar to those of natural mating. However, it is not fully efficient, as only liquid-stored semen is used, with a single boar inseminating about 2000 sows yearly. The use of liquid semen, moreover, constrains international trade and slows genetic improvement. Research efforts, reviewed hereby, are underway to reverse this inefficient scenario. Special attention is paid to studies intended to decrease the number of sperm used per pregnant sow, facilitating the practical use of sexed frozen-thawed semen in swine commercial insemination programs. (C) 2015 Elsevier Inc. All rights reserved.
Funding Agencies|European Regional Development Fund; Spanish Government (MINECO-FEDER) [AGL2012-39903, MINECO AGL2015-69738-R]; Swedish Research Councils VR [2011-6353]; FORMAS, Stockholm, Sweden [2011-512]