PRODUCTION,CHEMICAL QUALITY AND USE OF DUCKWEEDS (LEMNACEAE) IN AQUACULTURE,WASTE MANAGEMENT,AND ANIMAL FEEDS

The vascular plants known as duckweeds have been the subject of intense interest during the past decade as an aquacultural crop, part of waste management systems, and as a feed supplement for aquatic and terrestrial animal stocks. Yields in high nutrient lagoons in regions with nine-month growing season average about 10 metric tons (dry)/hectare, with maximum yields of 12 metric tons projected from .04 hectare lagoons. Crude protein for duckweeds cultured on animal waste lagoons has ranged from 35 to 45% of the dry weight and all essential amino acids are present. Lysine is present in sufficient concentration to meet FAO reference standards for animal feeds, and methionine equals or exceeds recommended standards in specific clones of Lemna turionifera, L. minor, and Spirodela polyrrhiza. Minerals, fat, fiber, and carbohydrate levels are not excessive for most animal diets. Successful feeding trials have been conducted with several species of fish, ducks, swine, poultry, and cattle. A review of research indicates this family of plants holds high promise for producing high quality animal and human food world-wide, but the technology for controlled production under full-scale systems is incomplete.