Embryonic duplications in sheep.

Twenty-seven embryonic duplications were examined during a 3-year investigation into the causes of perinatal lamb mortality. Twenty of the 27 were anomalous twins with 19 being conjoined (diplopagus 9 and heteropagus 10). The various duplications were: haloacardius acephalus 1, diprosopus 2, dicephalus 2, dipypus 3, diprosopus dipygus 1, syncephalus dipygus 1, pygopagus parasiticus 1, heteropagus dipygus 3, melodidymus 6, polyury 4, penile duplication 2, and bilateral otognathia 1. Four lambs were living and the time of death of the others was: parturient 8, and post-parturient 15. Average dry weight of the lambs was 3.35 kg (range 1.59 to 5.45 kg). Breed distribution was: Merino 77.8%, Crossbred 14.8%, Dorset Horn 3.7%, and Corriedale 3.7%. The caudal region was involved in 10 of the conjoined twins (52.6%), anterior region in 7 (36.9%), and both anterior and caudal regions in 2 (10.5%). Associated defects were present in 70.4% of the 27 lambs, the most common being atresia ani.