For transplantation of hea in human being, which of the animal hea has been used

Pigs (Sus scrofa domesticus) are currently thought to be the best candidates for organ donation. The risk of cross-species disease transmission is decreased because of their increased phylogenetic distance from humans. They are readily available, their organs are anatomically comparable in size, and new infectious agents are less likely since they have been in close contact with humans through domestication for many generations. Current experiments in xenotransplantation most often use pigs as the donor, and baboons as human models. Ref : internet