Embryo cloning by nuclear transfer: experiences in sheep

Pregnancy and Neonatal Care of SCNT Animals

“…The percentages of live offspring at birth and at 1 month were a ratio between the number of live offspring and the total number of transferred embryos. Data from pigs are from Schmidt et al Schmidt et al, (2010Schmidt et al, ( , 2011 and Schmidt, unpublished 2012. Results are based on results from goat cloning publications (Baguisi et al, 1999;Baldassarre et al, 2003Baldassarre et al, , 2004Baldassarrre, 2012;Behboodi et al, 2004Behboodi et al, , 2005Blash et al, 2012;Chen et al, 2007;Colato et al, 2011;Folch et al, 2009;Keefer et al, 2001Keefer et al, , 2002Lan et al, 2006;Liu et al, 2011;Loi et al, 1999;Nasr-Esfahani et al, 2011;Ohkoshi et al, 2003;Reggio et al, 2001;Tang et al, 2011;Wells et al, 2011) that resulted in the birth of 322 cloned kids (1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011), considering cell types (adult or fetal cells), genetic modifications (transgenic or wild-type cells), oocyte source (in vivo-or in vitro-matured oocytes), and day of estrous cycle and site of embryo transfer (day 1-2 into the oviduct or days 7-8 into the uterus).…”

“…The care of sheep and goats is generally comparable to that of cattle. Table 9.2 presents a retrospective analysis of goat cloning publications (Baguisi et al, 1999;Baldassarre et al, 2003Baldassarre et al, , 2004Baldassarre et al, , 2012Behboodi et al, 2004Behboodi et al, , 2005Blash et al, 2012;Chen et al, 2007;Colato et al, 2011;Folch et al, 2009;Keefer et al, 2001Keefer et al, , 2002Lan et al, 2006;Liu et al, 2011;Loi et al, 1999;Nasr-Esfahani et al, 2011;Ohkoshi et al, 2003;Reggio et al, 2001;Tang et al, 2011;Wells et al, 2011), with a cloning efficiency (1.3-3.4%) similar to other species and a postnatal survival rate ranging from 68.6% to 80.4%. The transfer of early-stage cloned goat embryos into the oviducts, resulting in a mean pregnancy rate of 34.4% (360/1047) on days 28-45 of gestation and a kidding rate of 58.9% (212/360), appears to be more efficient in producing live offspring than the transfer of in vitro-cultured morulae/blastocysts into the uterus, resulting in 17 (21.5%) pregnancies on days 30-40 of gestation, of which 9 (50.0%) went to term and yielded 10 cloned kids born, with no difference between the two methods in pre-and postnatal survival.…”

The use of multiple ovulation, embryo cryopreservation and embryo transfer techniques to facilitate movement of genetic material between countries

“…However, commercial application to the sheep industry did not occur until late 80's (Ishwar andMemon 1996, Naqvi et al 2001). In principal, MOET is a tool for genetic improvement aiming to identify genetically superior female animals and enabling them to have more offspring than would be possible naturally (Ishwar and Memon 1996, Loi et al 1999, Cognie 1999, Bari et al 2000. McKelvey (1999) stated that MOET has the potential to double the rate of genetic improvement in a given population through increasing selection intensities and decreasing generation intervals.…”

“…However, the application of MOET techniques to small ruminants has been much more slower mainly due to the lower economic value of these animals but also due to difficulties as a result of the reproductive anatomy of such animals (Armstrong and Evans G 1983, McKelvey et al 1985, McKelvey 1986, Ishwar and Memon 1996, Loi et al 1999. Overcoming such difficulties is therefore important not only as a method of increasing the number of elite animals in a herd but also from an economical and practical point of view provided that limitations are understood.…”