Birth of a monozygotic cattle twin following non surgical transfer of a single 7 day old embryo

A female twin was born after non-surgical transfer of one 7 day old embryo to the uterus of a synchronized receptor heifer. To prove the monozygocity of the twin, the hemotype was analysed (10 blood group systems and the polymorphic blood substances). The complete hemotype was identical in both twin calves. The probability that an identical genotype in a dizygotic twin could occur only by chance was calculated to be 23.8 x 10(-8). The bisectioning of the embryo most probably occurred during hatching at about day 8.