Frequency of chromosomal abnormalities in early embryos of the domestic sheep (Ovis aries).

Embryos or unfertilized eggs were collected 2 or 3 days post coitum from mature sheep of various breeds and crosses. The karyotypes of 89 of the 376 collected were established. There were 44 embryos with 2n = 54XX, 30 with 2n = 54XY;1 was a 2n/1n mouse; 4 had 2n + 1 chromosomes giving an incidence of trisomy of 4.7%; and 1 unfertilized egg had n = 28. The incidence of chromosomal abnormalities was 6%, and 1.3% of the eggs or embryos had a cracked zona pellucida.