Abstract Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the efficacy of Biomin® C5, which consists of a preparation containing viable cells of Enterococcus faecium DSM 33761, Pediococcus acidilactici DSM 33758, Bifidobacterium animalis DSM 16284, Limosilactobacillus reuteri DSM 33751 and Ligilactobacillus salivarius DSM 16351, as a zootechnical feed additive (functional group: gut flora stabilisers). The additive is intended to be used for chickens for fattening, chickens reared for laying, turkeys for fattening, turkeys reared for breeding and minor poultry species for fattening or reared for laying/breeding at a use level of 1 × 108 CFU/kg complete feed or 5 × 107 CFU/L in water for drinking. In a previous assessment, the FEEDAP Panel concluded that the additive is safe for the target species, consumers and the environment but could not conclude on its efficacy due to insufficient data. The applicant provided three long‐term trials in chickens for fattening to address the data gaps in the efficacy assessment. Based on the results of the trials in the previous and current applications, the FEEDAP Panel concluded that Biomin® C5 has the potential to be efficacious when supplemented either in the feed or water of chickens for fattening, and the conclusion was extrapolated to all poultry for fattening and reared for laying/breeding.