Provided is a functional feed additive having heartleaf houttuynia as a main ingredient, which is useful for disease prevention due to improved immunity, fleshiness improvement, and the growth while having a different composition from that of a conventional feed additive. In addition, the functional feed additive of the present invention has abundant mineral ingredients, and prevents the quality degradation of a feed while allowing even intake of each raw material. In particular, the functional feed additive of the present invention having heartleaf houttuynia as a main ingredient, has excellent texture and marketability due to improved intramuscular fat content and red expression of a meat color in breeding of pigs. To this end, according to the present invention, the composition of the functional feed additive, composed of 75 to 95 wt% of heartleaf houttuynia, 1 to 5 wt% of eucommia, 1 to 5 wt% of acanthopanax, 1 to 5 wt% of ganoderma lucidum, 1 to 5 wt% of gardenia fruit, and 1 to 5 wt% of adlay, is prepared by washing and naturally drying the composition. The dried composition is ground with a grinder to be pulverized into particles having the size of 0.05 to 0.2 mm, and powder is added to a mixed feed to provide the feed by 10 to 20 g for each time twice a day. In addition, in case of calves, 10 to 20 g of the powder is mixed with 40 to 80 ml of water for each time to provide the feed twice a day. Also, the powder is processed in a pellet form using a molding machine, a filtered salty water is boiled up to 100°C to be sterilized, and is cooled and sprayed to a pellet so as to be coated by 0.1 to 1 wt% with respect to the pellet, and the dried pellet is added in a ratio of 0.1 to 1 wt% to the mixed feed to be used.본 발명은 종래의 가축 사료 첨가제와 구성을 달리하면서도 면역력의 증진으로 질병예방과 육질개선 및 성장에 유용한 약모밀을 주성분으로 하는 기능성 사료 첨가제를 제공한다. 또한 본 발명은 미네랄 성분이 풍부할 뿐만 아니라 각 원료의 고른 섭취와 함께 사료의 품질저하를 방지할 수 있는 기능성 사료 첨가제를 제공한다.특히, 본 발명은 돼지 사육에 있어 근내지방 함량 향상과 붉은 육색의 발현으로 식감 및 상품성이 우수한 약모밀을 주성분으로 하는
