Image: IBEX® EVO® + L7HD, in a Holstein cow
Mummification in bovine fetuses has an incidence of less than 2%. It occurs when there is fetal death for any number of reasons (Trichomoniasis and BVD infections have been specifically implicated as causes), but the CL is retained, the cervix stays closed, and there is no bacteria or oxygen present in the uterus to cause maceration.