Abstract: Provided is a method for producing a feed additive raw material that can be used as a raw material of a feed additive for improving the palatability of feed and is capable of stably culturing animalcules containing a large amount of amino acids. A method for producing a feed additive raw material, comprising: a first biological treatment step of preparing a first biologically treated liquid containing dispersible bacteria by introducing an organic wastewater containing 40 wt % or more of protein to a first biological treatment tank and performing aerobic biological treatment with bacteria; a second biological treatment step of preparing a second biologically treated liquid by introducing the first biologically treated liquid to a second biological treatment tank and performing activated sludge treatment; and a sludge separation step of taking out part of the tank sludge from the second biological treatment tank as the feed additive raw material.

Abstract: Provided are an inexpensive feed additive including a metazoan animal as a feeding stimulant, and a mixed feed including the additive. The feed additive contains a metazoan animal or an aerobically biotreated sludge containing a metazoan animal. The content of the metazoan animal in the feed additive is 1 wt % or more on dry basis, and the content of a free amino acid in the feed additive is 0.5 wt % or more on dry basis. The metazoan animal is preferably based on rotifers. The mixed feed includes the feed additive and a feedstuff with the content of the feed additive of 0.1 to 30 wt % on dry basis.