The present invention provides a functional feed additive containing Houttuynia cordata Thunb., which is useful for growth and prevention of diseases due to enhancement of immunity, as a main ingredient. To this end, the present invention is obtained by: washing a composition of a functional feed additive, which contains 80-94 wt% of Houttuynia cordata Thunb., 3-10 wt% of gardenia seeds, 1-5 wt% of eucommia bark, 1-5 wt% of Ganderma lucidum, and 1-5 wt% of acanthopanax, and naturally drying the same； pulverizing the dried composition using a pulverizer into particles having a size of 0.05-0.2 mm； and adding the powder to assorted feed at a ratio of 0.1-1 wt% to be used. Also, in the case of calves, 10-20 g of the powder is added to 40-80 ml of water per feed to be fed twice a day. In addition, the powder is processed in a pellet form using a molding machine, and filtered salty water is boiled up to 100°C to be sterilized and cooled, is sprayed and coated onto pellets, and is then added to assorted feed in a dry state to be used. According to the technical configuration of the present invention, the supply of functional feed additives made of compositions such as Houttuynia cordata Thunb., gardenia seeds, eucommia bark, Ganderma lucidum, acanthopanax, and the like prevents diseases by improving antibacterial performance and immunity, and shortens a breeding period by promoting growth, thereby greatly contributing to an income increase of farm households. In particular, when the functional feed additive is fed to calves, the prevention of diseases causing diarrhea can be expected through the enhancement of antibacterial performance and immunity. In addition, according to the present invention, the powder is formed in a pellet form to coat salty water, thereby providing abundant minerals and preventing degeneration of feeds.본 발명은 면역력의 증진으로 질병예방과 성장에 유용한 약모밀을 주성분으로 하는 기능성 사료 첨가제를 제공한다. 이를 위하여 본 발명은 기능성 사료 첨가제의 조성물인 약모밀 80~94중량%, 치자 3~10중량%, 두충 1~5중량%, 영지 1~5중량%, 오가피 1
