The spontaneous occurrence of aortic arch and cardiac malformations in the white Leghorn chick embryo (Gallus domesticus).

Spontaneous aortic arch and cardiac malformations occur in White Leghorn chick embryos at a relatively high rate. Although this breed of Gallus domesticus is widely used for biomedical and biological research, no previous study has recorded the incidence of these defects. We found aortic arch malformations in 7.1% (14 of 196) and ventricular septal defects in 11.7% (23 of 196) of living embryos. Defects occurred alone or as a combined pattern. Our findings suggest that the cardiovascular defects in the chick embryo documented in past studies may, in some cases, have been part of normal spontaneous occurrence, rather than the major result of experimental manipulation.