Abstract: The present invention relates, in general, to a method of enhancing the production performance of avians, by administering to a bird a heterologous protein comprised of inhibin protein, or a fragment thereof, and a carrier protein. The present invention also relates to a method of enhancing the production performance of avians, by administering to a bird a fusion gene product comprising a gene encoded for the expression of alpha-subunit avian inhibin protein, or a fragment thereof, and a gene encoded for the expression of a carrier protein. An effective amount of the heterologous protein or fusion gene product is administered to an animal such that an immunological response occurs in the animal against the heterologous protein. The present invention further relates to the above heterologous protein and fusion gene product, and to methods of producing the same.