Additives for crustacean or fish feeds and feeds

摘要

A feedstuff additive for crustaceans and fishes, characterized in that it is prepared from gram-negative bacteria, that it has a molecular weight of 5000 +/- 2000 as measured by SDS-PAGE method using a protein marker, that it is substantially free of high molecular weight lipopolysaccharide, that it contains a low molecular weight lipopolysaccharide as an effective component and that it is capable of activating immunity and preventing infection in crustaceans or fishes ; and a feed for crustaceans and fishes comprising the above feedstuff additive.