We thank H. De Greve for advice with the anti-F4-ETEC VHHs and sharing purified antigen. We thank E. Van Lerberge and J. Nolf for overall technical support, particularly for upscaling seeds, antibody expression analysis and protein analysis. We thank S. Brabant for help with blood sampling and analysis of the seroconversion, R. Cooman for animal caretaking and management of the stables and U. Van Nguyen for performing the villous adhesion assay. We thank K. Wang of Iowa State University for the soybean transformation, J. Haustraete of the Protein Service facility of VIB for large-scale production of Pichia cultures and D. De Paepe and K. Coudyser of ILVO food pilot for lyophilization of Pichia spent medium. For access to weaned piglets we acknowledge the farms of K. Devolder and ILVO, and thank their resident animal husbandry teams. We are grateful to S. Millet for feed consultation and access to large industrial mixers for feed formulation at ILVO, and T. Moravec of the Institute of Experimental Botany Prague, J. Mar Björnsson of ORF Genetics and J. Van Huylenbroeck of ILVO for kindly leasing additional greenhouse space for scaling up soybean seeds. The authors would finally like to thank M. Vuylsteke and V. Storme for help with the statistical analysis and A. Bleys for help with editing the manuscript. This work was supported by an IWT-innovation fellowship (No. IM-140851) awarded to V.V., co-sponsored by AVEVE Biochem, AVEVE Group. J.P. received a PhD stipend from the Research Foundation Flanders (FWO project grant No. G0C9714N). B.L. has been supported by the European Research Council’s consolidator grant awarded to N.C. (No. ERC-2013-CoG-616966). Overall we would like to acknowledge institutional funding and support from Ghent University and VIB.