Feed additive for promoting growth and intestinal development of livestock and poultry, and preparation method and application of feed additive

The invention belongs to the technical field of feed additives, and discloses a feed additive for promoting growth and intestinal development of livestock and poultry, and a preparation method and application of the feed additive, aiming at improving the structure of intestinal flora of livestock and poultry, overcoming the adverse effects, caused by antibiotics, on the growth of livestock and poultry, and promoting the healthy growth of livestock and poultry. The feed additive is prepared from head cabbage slurry and solid bacillus subtilis according to a mass ratio of 500 to (1-3); the feed additive is prepared by adding 0.2-0.6g of the solid bacillus subtilis into every 100g of the head cabbage slurry, and evenly mixing; when being used as an additive for livestock and poultry feed, 10-40g of the feed additive is added into every 1000g of the feed. The feed additive is wide in material source, adequate in nutrients and high in digestibility and utilization rate; when being used as the additive for the live