Written by: Dr. Jacquie Jacob, University of Kentucky
Seaweeds, which can be used in poultry diets, are marine algae, or vegetation of the sea. Typically, they are classified as green, brown, or red.
- Green algae include species of the Chlorella, Chlamydomonas, Enteromorpha, Spirogyra, and Ulva genera. The green color comes from chlorophyll, beta-carotene, and various xanthophylls. Green algae store their energy mostly as starch but also as some fats or oils. Green algae require sufficient sunlight to survive, so they usually grow in shallow waters. Common green algae, such as sea lettuce (Ulva) and green sting lettuce (Enteromorpha), are used as food.
- Brown algae include species of the Laminaria, Saccharina, and Fucus genera 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). Brown algae store their energy as complex carbohydrates, sugars, and higher alcohols. About 1,500 to 2,000 species of brown algae exist. Kelps (Laminaria) are the main seaweeds grown in the northeastern United States.
- Red algae include species in the Palmaria, Delesseria, Chondrus, and Corallina genera. The red color is the result of the pigments phycoerythrin and phycocyanin, which mask the other pigments. Red algae store their energy mainly as starch. Red algae make up the largest group of seaweeds (5,000 to 6,000 species) and are found throughout the world. Most red algae grown are used in 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. Recently researchers have been looking at the potential of using seaweed in medicine. Other products developed from seaweed include fertilizers, skin care products, and animal feed.
To produce seaweed meal for use in animal feed, brown seaweeds are collected, dried, and milled. Because much of the protein and carbohydrates in seaweed are not digestible in non-ruminants, the nutritional value of seaweed for poultry is as a source of minerals and vitamins. In Norway, where seaweed meal has been produced for animal feeds since the 1960s, seaweed meal is considered to have 30 percent of the nutritive value of grains. The minerals in seaweed meal include potassium, phosphorus, magnesium, calcium, sodium, chlorine, and sulfur as well as the trace elements (elements required in trace amounts) zinc, cobalt, chromium, molybdenum, nickel, tin, vanadium, fluorine, and iodine. The mineral content of some seaweeds represents 30 percent of the dry matter weight. The vitamins in seaweed meal include ascorbic acid, tocopherols, and some B vitamins.
Seaweed meal can be added to poultry diets in a ratio of up to 5 to 15 percent of the diet, depending on the species of seaweed and the species and age of the animal. One use of seaweed in the diet is as a pellet binder—including seaweed as up to 3 percent of the diet improves the hardness of the pellet. With duck diets, brown seaweeds can be included as up to 12 percent of the starter diet and up to 15 percent of the finisher diet without adversely affecting growth performance or meat quality. In addition, some research shows that feeding seaweed meal and sardine oil together to chickens results in reduced levels of egg cholesterol and increased omega-3 fatty acid levels with no adverse effect on taste.
Besides seaweed meal, other forms of seaweed can be beneficial to animals. For example, intact brown seaweed, as well as seaweed extracts, have been shown to promote prebiotic activity in pigs. Prebiotic compounds are indigestible compounds that stimulate the growth and/or activity of beneficial microorganisms in the digestive tract. Growth or activity of these microorganisms, in turn, has health benefits for the animal.