PURPOSE: A feed additive for pigs of chickens using 5-aminolevulinic acid, Sanguisorba officinalis, and Rhus japonica is provided to replace antibiotic for preventing the infection caused by Escherichia coli. CONSTITUTION: A feed additive for pigs of chickens contains 5-aminolevulinic acid and a mixture fermented extract of Sanguisorba officinalis and Rhus japonica as active materials in a weight ratio of 1:50-500. The mixture fermented extract is obtained by fermenting the Sanguisorba officinalis and Rhus japonica with Aspergillus oryzae or Lactobacillus casei.