Generation of identical twin piglets following bisection of embryos at the morula and blastocyst stage.
Porcine morulae and blastocysts were microsurgically bisected and the resulting zona pellucida-free demi-embryos were either cultured in vitro for 48 h or transferred after 24 h of culture into--24 h asynchronous recipients. All demi-embryos were evaluated according to morphological criteria and classified into three categories (excellent, fair or degenerated). The average diameter and the number of cells were determined. Of 1162 bisected embryos, 764 pairs (66%) were evaluated as transferable after 24 h of culture in vitro. The average diameter after 48 h of culture in vitro was different (P < 0.01) among demi-embryos of the three morphological categories as was the number of cells. The greatest diameter and the greatest number of cells were found in demi-embryos classified as morphologically excellent. A total of 22 of 27 recipients (81.5%) remained pregnant and 21 recipients delivered 126 piglets of which six were stillborn. The survival rate of demi-embryos in farrowing recipients was 21.2% (126 of 594). Litter size was significantly reduced in recipients after transfer of demi-embryos compared with that of mated controls (6.0 +/- 2.5 versus 10.8 +/- 2.1 piglets). Similarly, the postpartum losses of piglets were higher in the experimental than in the control gilts (26.7% versus 11.6%). Duration of gestation, average birth weight and daily weight gain were not affected. Among the 126 piglets, seven pairs of identical twins (2.3% of 311 transferred pairs) were identified using several genetic markers in blood (blood groups, polymorphic enzymes and plasma proteins) in a total of 25 gene loci. DNA fingerprinting revealed an identical banding pattern between the two partners of each of the seven pairs. Birth and weaning weight as well as daily weight gain varied considerably between monozygotic partners.
Reichelt
B
B
Institut für Tierzucht und Tierverhalten (FAL), Neustadt, Germany.
Niemann
H
H
D000818:Animals; D000831:Animals, Newborn / Q000235:genetics*; D001755:Blastocyst / Q000166:cytology; D001947:Breeding / Q000379:methods*; D002478:Cells, Cultured; D004622:Embryo, Mammalian / Q000601:surgery; D005260:Female; D008297:Male; D008866:Microsurgery / Q000379:methods; D009028:Morula / Q000166:cytology; D013552:Swine; D013997:Time Factors; D014430:Twins, Monozygotic