Design, development, and application of a non-surgical deep uterine embryo transfer technique in pigs

Embryo transfer (ET) is a procedure that involves the recovery of embryos from the reproductive tract of genetically superior donor females and the transfer of these embryos into the uterus of recipient females for the birth of live offspring. This technology has numerous important applications in farm animal production, including genetic improvement and the national and international movement of genetic material (i.e., embryos) with minimal risk of disease transmission, reduced transportation costs, and no effect on animal welfare compared with the transport of live animals. In addition, ET is fundamental for other biotechnologies related to the in vitro production and manipulation of embryos. Despite these important applications, the commercial use of ET widely varies among species. While ET has been extensively used for commercial purposes in cattle for more than 30 years, its use in ovine, caprine, and particularly porcine species is currently very limited or nonexistent in contrast to other biotechnologies (Rodriguez-Martinez, 2007). One of the most important factors in the ability to exploit ET technology at a commercial level is the ability to collect the embryos from the donors and to transfer them to the recipients using procedures that can be easily performed under field conditions. As stated by Betteridge (2006), “the simpler the technique, the wider its applicability. ” A clear example of this statement is the evolution of ET in cattle, which has been excellently reviewed by Betteridge (2003). In the 1950s, the first efforts to transfer embryos into the uterus of a recipient with a non-surgical procedure were ineffective (Lamming and Rowson, 1952). At that time, surgical methods for embryo collection and transfer in cows were well developed. However, ET did not grow in popularity until non-surgical methods were developed. By the 1960s, the first calf born using non-surgical ET was obtained (Mutter et al., 1964), and new methods of depositing embryos using non-surgical procedures were reported (Rowson and Moor, 1966). During the 1970s, non-surgical methods for collection and transfer completely replaced surgical methods, and the procedures were improved with the development of different non-surgical catheters and protocols. These investigations resulted in a non-surgical, practical procedure for ET in cattle, leading to an explosive increase of commercial ET, today a booming worldwide business. Currently, ET of in vivo (or in vitro) produced embryos to the uterus of a recipient cow is easy and reliably performed by transcervical intrauterine deposition, with > 60% of pregnancy rates (reviewed in RodriguezMartinez, 2012). A major factor contributing to this development was the practical necessity of avoiding surgery if ET was to become practicable in the field. Necessity really was the mother of invention (Betteridge, 2003). At least 100,000 donor females were flushed in 2010, with more than 730,000 embryos collected and almost 600,000 embryos transferred, 55% of which were frozen. In contrast, the number of sheep and goat embryos collected in that year was less than 5% and 0.1%, respectively, of that recorded for cattle. Unfortunately, no swine ET activity was reported by any country in 2010, although the numbers of flushings reported for 2008 and 2009 in the US were 134 and 9, respectively. In addition to commercial and market factors, current ET in small ruminant and pigs are performed Design, development, and application of a non-surgical deep uterine embryo transfer technique in pigs