Photo credit: Khamis killei John (South Sudan)
Review: Abdel Rahman El Gamal (Founder of the website)
This photo was taken in an aquaculture facility in China
Introduction: Duckweeds are macrophytes which belong to the Lemnaceae family. They are small green flowering plants which grow as small floating colonies on the surfaces of quiet water bodies. The plant reproduces vegetatively with an extreme and rapid multiplication especially under proper conditions. It is estimated that duckweed can produce between 10-30 tons dry matter/ha/year, depending on the species, climatic conditions, available surface area, amount of nutrient and management.
These plants are almost all leaf, having essentially no stem tissue, with very fine roots. In nature, duckweeds serve as food for many species of fish and aquatic birds.
Nutritive value of duckweed: Duckweed enjoys a protein content of about 20-45% based on dry weight, depending on the nitrogen supply and has a better array of essential amino acids than most other vegetable proteins and more closely resembles animal protein. With the exception of the amino acid, methionine, the levels of essential amino acids duck weed surpassed the FAO reference pattern. Similarly, the levels of minerals in duckweed are usually high.
With its high protein content, its amino acid profile, its mineral content, and the low fiber in its leaves (5% in dry matter) as well as the little to no indigestible material recommended the duckweed as a good dietary supplement and nutrient source for even monogastric animals, poultry and fish.
Potential use of duckweed in fish feed: Formulated fish feed especially the protein content represents a major cost in fish production. Aquaculturists and in particularly nutritionists have been trying through trials and research projects to find possible alternative low-cost sources of fish feed especially animal protein.
Duckweed with its nutritive merit has been explored in many studies and was found a promising especially when partially replacing a part of fish meal which represents the most expensive component in fish feed. The research findings have been applied in fish farming for number of fish species including tilapia, Chinese carps and others whereas a replacement of (up to 25%) of fish meal has been successfully practiced without negative impacts on growth or production. Tilapia being omnivore fish has been found is a good candidate for duckweed utilization due to their feeding habits that allow them to benefit from plant protein.
Higher utilization efficiency has been achieved when duckweeds are grown separately and then provided to the fish.
