by Krystal K Lum, Jonggun Kim and Xin Gen Lei, Cornell University, USA
lthough the use of whole microalgae in animal diets has long been studied, the de-fatted biomass of microalgal species, derived from biofuel production research, has only recently shown feasibility in replacing corn and soybean meal in animal diets.
While the nutritional profiles of microalgae vary considerably with the species used, a large majority are characterized by protein, carbohydrate, and lipid contents that are comparable, if not superior, to conventional feedstuffs. Dietary soybean meal typically contains up to 48% crude protein, with a relatively well-balanced amino acid profile. The diversity of microalgae makes certain species amenable to cultivation for diet-specific needs of humans and animals.
A commonly cultivated algae species for human consumption: S. maxima, contains high levels of vitamin B1, vitamin B2, and β-carotene, and up to 71% crude protein with sufficient concentrations of all essential amino acids except for the sulfur-containing ones. Since protein is considered to be the most expensive nutrient in animal feed, developing natural alternatives to soybean meal may be cost competitive.
Among all dietary amino acids, lysine and methionine are the first and second limiting amino acids. Many microalgal species contain relatively high amounts of lysine, but are somewhat deficient in the sulfur-containing amino acids: cysteine and methionine. To maximise amino acid utilisation by animals, diets are typically formulated by mixing different feedstuffs to balance amino acid profiles and (or) by supplementing synthetic amino acids to meet their nutrient requirements.
This article has been excerpted from the original paper: “Dual potential of microalgae as a sustainable biofuel feedstock and animal feed,” published in the Journal of Animal Science and Biotechnology 2013, 4:53.