Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the efficacy of Bacillus subtilis FERM BP‐07462, Enterococcus lactis FERM BP‐10867 and Clostridium butyricum FERM BP‐10866 (BIO‐THREE®) as a zootechnical feed additive to be used as a gut flora stabiliser for chickens for fattening and reared for laying, turkeys for fattening and reared for breeding, and all avian species for rearing/fattening or reared for laying/breeding. In a previous opinion, the FEEDAP Panel could not conclude on the efficacy of BIO‐THREE® for the target species at the proposed conditions of use. The applicant has provided a new study in chickens for fattening as supplementary information to support the efficacy of BIO‐THREE® for the target species. Considering the previously submitted studies and the new submitted trial, the Panel concluded that the additive is efficacious for chickens for fattening and reared for laying, turkeys for fattening and reared for breeding, and all avian species for rearing/fattening or reared for laying/breeding under the proposed conditions of use.