Transgenes encoding exogenous antibodies are stably integrated into donor cells and are present in the somatic tissue of chimeric birds. The transgenes encode exogenous antibodies and are preferably expressed in the oviduct for collection in the egg. Tissue specificity is provided by selecting the content of the transgene accordingly. Birds whose genome is comprised of trangene-derived exogenous antibody-encoding DNA express exogenous antibodies having desirable chemical properties with increased therapeutic utility compared to antibodies derived from bacterial expression systems.