Abstract: The present disclosure provides a feed additive for domesticated animals that is capable of increasing feed performance, as well as associated methods for promoting growth and zootechnical performance in domesticated animals. The animal feed additive provided contains Total Lignans standardized in the contents of Furoguaiacin-like compounds and Guaiacin-like compounds. The present disclosure also describes methods for improving growth via the dietary inclusion of Total Lignans standardized in Furoguaiacin-like compounds and Guaiacin-like compounds.