Bloo meal is dried, powdered blood used as a high-nitrogen fertilizer. It is one of the highest non-synthetic sources of nitrogen and if over-applied it can burn plants with excessive ammonia. Blood meal is completely soluble and can be mixed with water to be used as a liquid fertilizer. It usually comes from cattle as a slaughterhouse by-product. It can be spread on gardens to deter animals such as rabbits, or as a compost activator. It may also be used as an animal food supplement.