Congenital defects, or those that exist at birth, arise from a variety of causes. Those causes include genetics, viral or bacterial disease of the calf or dam, toxic substances to which the dam was exposed during gestation, and others. While there is a possibility that the congenital defect is genetic, it is very unlikely. More likely causes are toxic substances or a variety of viral diseases that have been shown to cause fetal harm.

Most congenital defects that are genetic in origin are recessive in nature. Recessive traits require that an animal have two copies of the deleterious gene; that is, one copy inherited from each parent. Matings of unaffected carrier parents result in affected calves for one calf out of four. In your example, the previous calves from this cow may be from breedings of different, non-carrier bulls. And future breedings of this cow with same bull may not produce another calf with this defect. Since it is not infectious, no treatment is necessary for the cow.