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.
Algae are typically classified as green, brown, or red. All algae contain one or more type of chlorophyll, the pigment involved in photosynthesis. Green algae 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. Chlorella and Spirulina are examples of green algae. Brown algae get their brown color from 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. Red algae get their color from the pigments phycoerthrin and phycocyanin, which mask the other pigments. Starch is typically the main form of energy storage for red algae.
Microalgae have the potential to be an enormous biological resource. The same amount of land for growing corn would produce 125 times more protein from the microalgae Spirulina. Unlike the higher plant species, algae can be harvested daily, year-round.
Chlorella is one the most commonly produced microalgae species and can be adapted to different growth conditions. Spirulina is also cultivated around the world, primarily for use as a health supplement.
Chlorella and Spirulina are both microalgae commonly used as human health supplements. Chlorella is a spherical, single-celled microorganism with a nucleus. Spirulina is a spiral-shaped, multi-celled plant—100 times bigger than the Chlorella cell but with no true nucleus. Chlorella grows primarily in fresh waters and, because of its size, requires more sophisticated equipment to harvest. Spirulina, on the other hand, grows mainly in highly alkaline waters where many other organisms will not grow.
Another microalga studied to a lesser extent is Schizochytrium. Supplementing layer diets with a commercial Schizochytrium-containing product was shown to increase the DHA (docosahexaenoic acid) content of the eggs (Abril and Barclay, 1998). DHA is an essential omega-3 fatty acid that is important, among others, in the formation of the brain and nervous system of infants. Similarly, supplementation of layer diets with Porphyridium (a red microalga) has been shown to reduce cholesterol and increase the omega-3 content of eggs (Ginzberg et al., 2000).
Spirulina has been used as a human food as far back as the Aztecs. It is generally accepted to be a good source of protein (60-70%), vitamins (including vitamin B12), essential amino acids (1.30-2.75% of dry matter for methionine and 2.60-4.63% of dry matter for lysine), minerals, essential fatty acids (include gamma-linolenic acid), and antioxidant pigments (Holman and Malau-Aduli, 2012).
Nutritionally, Spirulina and Chlorella are similar—although Spirulina has a slightly higher protein content. Chlorella is higher in antioxidants, and the vitamin B12 is more biologically available than that of Spirulina. Chlorella is a good source of lutein while Spirulina has none.
The metabolic pathways of Chlorella can be manipulated by changing the cultivation medium. It is possible to produce selenium-enriched Chlorella, which can be used to supplement the diet with a more biologically-available and less toxic form of selenium—an essential trace mineral.
It is generally accepted that intestinal microflora play an important role in maintaining animal health. Supplementation of poultry diets with Chlorella vulgaris has been shown to increase microbial diversity in the digestive tract, especially in the ceca (Janczyk et al., 2009). Most of the studies determining Chlorella inclusion levels in animal feeds have been associated with aquaculture. Based on a few studies on the inclusion in poultry feeds, a maximum of 10% is recommended (Ross and Dominy, 1990).
Research has shown that vitamin-mineral premixes are normally not required when Spirulina has been included in the feed (Venkataraman et al., 1994). In addition, chickens receiving diets supplemented with Spirulina had better health. This may be due to an enhancement of the immune function (Belay et al., 1996). Recommended inclusion levels in poultry diets are 5–10% (Toyomizu et al., 2001). Higher levels of inclusion will result in poor growth performance. Inclusion of Spirulina in layer diets has also been shown to reduce total cholesterol content of eggs while increasing omega-3 fatty acid levels (Sujatha and Narahari, 2011).
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.