The material isolated from adult bovine liver was proved to have the similar properties as chicken bursin. It promoted the immunity of chicken by increasing the production of antibodies and enhancing the development and differentiation of B lymphocytes when the material was injected into 13th and 15th days chick embryos. Furthermore, the present experiments revealed that the material isolated from adult bovine liver could strengthen chicken's defence ability against infectious bursal disease virus. These findings indicate that adult bovine liver may contain bursin-like factors.