Feed additive capable of preventing spotted-brown hens from laying soft shell eggs and method for preparing the same

The invention discloses a feed additive capable of preventing spotted-brown hens from laying soft shell eggs. The feed additive is prepared from, by weight parts, 15-20 parts of astragalus, 15-20 parts of codonopsis pilosula, 15-20 parts of largehead atractylodes rhizome, 15-20 parts of atractylodes lancea, 8-12 parts of epimedium herb, 8-12 parts of psoralea corylifolia, 8-12 parts of davallia mariesii, 15-20 parts of fleece flower root, 15-20 parts of rehmannia glutinosa, 15-20 parts of Chinese thorowax root, 15-20 parts of flax, 15-20 parts of glycyrrhiza uralensis and 20-30 parts of blending agents. The feed additive has effects of tonifying qi, the kidney and spleen, promoting digestion and supplementing calcium. The feed additive has obvious effects of preventing the spotted-brown hens from laying the soft shell eggs, the controlling experimental effective rate is over 98%; the feed additive is applied and popularized to 150000 test chickens, and the average effective rate is over 98%. The feed additive has obvious effects of preventing the spotted-brown hens from laying the soft shell eggs.