With the increasing demand for protein sources in animal feed, many nutritionists are considering the use of autotrophic algae to supply needed nutrients in livestock diets. However, the field of algae is growing rapidly and through heterotrophic algae, nutritionists are finding a more natural, pure sustainable source of DHA, and high-quality fatty acids that are not only providing needed nutrients, but are also revolutionizing the way we feed our livestock.

It’s not a stretch to say the time may come when feed mills will have a difficult time sourcing corn, soybean meal, cottonseed, urea, distiller’s grains, blood meal and/or fishmeal. With daily news articles focusing on how the agricultural industry can produce enough food to feed an additional 3 billion people by 2050, continue to meet the renewable fuels mandate, and provide safe, quality products for a more engaged consumer audience, the task for locating a secure source of protein may soon prove to be a daunting undertaking for the feed industry.

Algae, the new game changer

With these stakes at hand, many feed companies are starting to look beyond available protein sources on land to those in the sea. Algae, a buzzword in the biofuel industry five years ago, is the new game changer in the animal feed industry. One of nature’s most important and unique organisms, algae contributes to the air we breathe, producing nearly 50 percent of the oxygen in the atmosphere and directly supporting the ocean life, therefore playing a major role in global productivity.

There are an estimated 800,000 species of algae that range from single-celled microorganisms to multi-celled organisms, such as the 200-foot-long giant kelp. Algae produces carbohydrates, oils, protein, vitamins, pigments and organic materials. Since they are aquatic, algae grow much faster than land plants as they do not have to expend energy growing roots or supporting structures like trunks, leaves and stems. Without the need for support, algae can triple or quadruple their biomass every day. While land plants only grow in one direction, algae can grow in all directions. This rapid growth means that one acre of algae can produce the same amount of protein in a year as 21 acres of soybeans or 49 acres of corn.

Growth in the microalgae industry

While macroalgae (seaweed) dominates global aquatic plant production, the microalgae industry is growing rapidly as scientists continue to find new applications for the freshwater and marine species. Today, the freshwater Chlorella and Arthrospira are primarily used for human dietary supplements and ingredients for animal feed. Other species are used for the extraction of high-valued components such as vitamins, w-fatty acids, natural pigments and antioxidants.

Most commercial production of microalgae is done autotrophically in open, outdoor circulating raceways or ponds. Under autotrophic growing conditions, microalgae use light energy to fix carbon dioxide, their carbon source, into hydrocarbons with oxygen discharged as a waste product. However, poor light diffusion; microbial, chemical and physical contamination; downstream processing; and the growth of zooplankton and other species are all drawbacks of an open system.

Production methods

Photobioreactors (PBR) have improved productivity of autotrophic production through the careful control of growth limiting and environmental parameters. However, PBRs have not been deemed successful or economical for producing low-cost, high-volume end products for the feed industry.


The other commercial production method in growing algae is the heterotrophic system. Heterotrophic species get their energy from organic carbon compounds in much the same way as yeast, bacteria and animals. By eliminating light from the production process, any fermenter (such as those used for production of medicines, beverages and food additives) can be used for heterotrophic algal growth. Reaching 100,000 liters in size, these fermenters can generate large volumes of highly productive cultures, making them less expensive than the autotrophic system. 

Nutritional benefits

One of the main differences between autotrophic and heterotrophic systems is the added nutritional benefits from heterotrophic algae. The heterotrophic method maintains a closed, controlled system that provides a more consistent, traceable and pure algal product that is more beneficial for the feed industry. For example, by manipulating the physical and chemical properties of the cultural medium, several species of microalgae can overproduce and accumulate higher levels of specific fatty acids. Xu et al. (2006) demonstrated that C. protothecoides had a lipid content as high as 55 percent, approximately four times greater than when grown autotrophically.

In another study, Barclay et al. (1994) showed that omega-3 fatty acid productivity was two to three times higher when produced in heterotrophic rather than autotrophic conditions. Microalgae that contain large quantities of high-quality eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are now being commercialized as sustainable alternative sources to fish oil. By providing a clean and consistent source of omega-3 fatty acids and high-quality protein, heterotrophic microalgae offers more nutrition components to a diet than the autotrophic method.

Year-round harvesting

These microalgae are also able to offer more nutritional benefits for consumers. Besides seeing an increase in immunity, a decrease in mortality and increased litter size in their herds, producers who utilize feeds with this type of algae will also be able to further brand their products as value-added omega-3 enriched for consumers. 

Besides the nutritional improvement that microalgae can bring to feeds and food, it is the only biomass material that allows production with daily harvest all year around. This could bring more security to an ever-changing feed market and provide some options for feed mills around the world.