As a solution to the recurrent economic losses induced by F4 + ETEC-associated diarrhea, the Applicants have previously shown that the oligoclonal mix of new monomeric, dimeric and secretory lgAs-V HH anti-F4 + ETEC antibodies produced in the plant Arabidopsis, F4 + piglets protects against ETEC infection when administered in feed for pigs in a dose of 20 mg / pig / day. For further enhancement of these positive results, through the development of a feed directed to prophylaxis against ETEC F4 +, the ideal / active size of the VHH-IgA is to be determined, ie either monomer, dimer, or secretory IgA. Then the right platform for cost bulk production will be determined which must also comply with regulatory legislation. This will be achieved by the successive implementation of these objectives.