Immune responses of chickens fed the androgen analog mibolerone

Mibolerone, an androgen analog (17 beta-hydroxy-7-alpha, 17-dimethylestr-4-en-3-one), induces a slow but progressive involution of the bursa of Fabricius when fed to chickens at microng levels during the first 7 weeks of life. Chickens receiving mibolerone remained immunologically competent, evidenced by: 1) their antibody response to nonreplicating antigens and infectious antigens; 2) the number of antibody-producing cells in their spleens; 3) the stimulation of their peripheral leukocytes with the plant mitogen phytohemagglutinin; and 4) their capacity to resist challenge with Marek's disease virus and Newcastle disease virus after vaccinations with turkey herpes-virus and the B-1 LaSota strain. This, coupled with the fact that it prevents experimental lymphoid leukosis, makes mibolerone a potential agent to be used under field conditions for the control of lymphoid leukosis.