Dr. Jacquie Jacob Ph.D., University of Kentucky
NOTE: Before using any feed ingredient make sure that the ingredient is listed in your Organic System Plan and approved by your certifier.
Seaweeds are macroscopic algae that grow along the coastline of many different countries and represent a renewable resource. Norway has produced seaweed meal for animal feeds since the 1960s. Brown seaweeds are collected, dried, and milled. Since drying uses oil-fired furnaces, the price of seaweed meal varies with crude oil prices.
Algae are typically classified as green, brown or red.
Green algae include Chlorella, Chlamydomonas, Spirogyra, and Ulva species. They get their green color from chlorophyll, beta-carotene, and various xanthophylls. They store their energy as starch, with some fats or oils. Green algae require sufficient sunlight to survive, so are usually found in shallow waters. Common green algae like sea lettuce (Ulva) and green string lettuce (Enteromorpha) are used as food for humans.
Brown algae include Laminaria, Saccharina, Fucus, and Sargassum muticum. The brown color is due to the dominance of the xanthophyll pigment fucoxanthin, which masks the other pigments (chlorophyll, beta-carotene, and other xanthophylls). The brown algae store their energy resources as complex carbohydrates, sugars, and higher alcohols. There are about 1,500–2,000 species of brown algae. Kelp (Laminaria) is the main seaweed grown in the Northeastern United States. These are also used in food products for humans.
Red algae include Palmaria, Delesseria, Chondrus, and Coralline algae. The red color is the result of the pigments phycoerthrin and phycocyanin, which mask the other pigments. The main form of energy storage is typically as starch. Red algae are the largest group of seaweeds (5,000–6,000 species) and are found throughout the world. Most red algae are grown for use in human food products, especially in the Orient.
Seaweed farming is common in many coastal areas around the world. The most common use for seaweed is as human food. There has been some research evaluating the potential of seaweed in medicine. Other products developed from seaweed include fertilizers, skin care products, and animal feed. Seaweed meal is a good source of minerals and vitamins. The minerals include potassium, phosphorus, magnesium, calcium, sodium, chlorine and sulfur as well as the trace elements (required in minute amounts) zinc, cobalt, chromium, molybdenum, nickel, tin, vanadium, fluorine and iodine. The mineral content of some seaweeds represent 30% of dry matter weight. The vitamins in seaweed include ascorbic acid, tocopherols and some B-vitamins. Since much of the protein and carbohydrates are not digestible in non-ruminants, the nutritional value of seaweed is as a source of vitamins and minerals. In Norway, seaweed meal is considered to have 30% of the nutritive value of grains.
The term seaweed encompasses many different species of macroalgae. The composition will differ between species and where they are harvested from. In general, seaweeds are included in animal diets as a natural source of protein, vitamins and essential amino acids (Kumar and Kaladharan, 2007). They are high in vitamins A, B1, B12, C, thiamine, and riboflavin. Seaweeds are also natural sources of the antioxidant ß-carotenes and tocopherols. Seaweeds are also a source of omega-3 fatty acids and can be a natural source of minerals, with minerals accounting for up to 36% of the dry matter (Burtin, 2003). Seaweeds can be excellent sources of the macrominerals sodium, calcium, magnesium, potassium, chlorine, sulfur and phosphorus and the microminerals iodine, iron, zinc, copper, selenium, molybdenum, fluoride, manganese, boron, nickel and cobalt (Madhusudan et al., 2011). Most of the brown algae are low in protein (5-15%) and slightly higher (10-30%) in green and red seaweeds (Burtin, 2003).
Seaweed does contain phlorotannins, which are similar to the tannins found in terrestrial plants but derived from a different base molecule (Burtin, 2003).
Seaweed meal can be added to poultry diets up to 5-15% of the diet, depending on the species of algae and the species and age of the animal. Seaweed can be included in the diet as a pellet binder. Inclusion up to 3% of the diet improves the hardness of the pellet (El-Deek and Brikka, 2009b).
With duck diets, brown seaweeds can be included in the starter and finisher diets up to 12% and 15%, respectively, without adversely affecting growth performance and meat quality. Red seaweed (Polysiphonis spp) can be included up to 15% in duck starter and grower diets with no adverse effects on growth performance or carcass quality (El-Deek and Brikka, 2009a).
Intact brown seaweed, as well as seaweed extracts, have been shown to have prebiotic activity in pigs. Prebiotics are indigestible compounds that stimulate the growth and/or activity of beneficial microorganisms in the digestive tract. This in turn has health benefits for the animal. There is some research reporting that feeding seaweed meal and sardine oil together resulted in reduced levels of egg cholesterol and increased the omega-3 fatty acid level with no adverse effect on taste (Carillo et al., 2012).
Some studies have indicated that including as little as 10% seaweed in a broiler diet reduced growth performance (Ventura et al., 1994).
This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by members of the eOrganic community. Always check with your organic certification agency before adopting new practices or using new materials. For more information, refer to eOrganic's articles on organic certification.