Potential use of microalgae products in swine diets
J.A. Mielke, Y. Ma, M. Saqui-Salces, P.E. Urriola, C. Chen, and G.C Shurson
One of the most significant long-term challenges in the feed and food animal production industries is to produce more food using fewer feed resources that is more sustainable and minimizes negative impacts on the environment. Growth of the world population of people and increased consumption of animal derived food products are causing a greater need to improve productivity and sustainability of food animal production systems. The demand for corn and soybeans, two of the most widely used crops in food animal production systems and for biofuel production, is greater than it has ever been, and it is expected to increase by 110% by the year 2030, thus increasing the need for greater productivity or additional land to grow crops (Coyle, 2014, Lum et al., 2013). Over 35% of corn and soybean production is used for animal feed in the world today, which signifies a challenge for animal production systems to reduce their carbon footprint (Lum et al., 2013). In order to reduce the negative environmental impacts on both food production systems and the environment, a new generation of sustainable, alternative feed ingredients is being investigated. Microalgae are at the forefront of this new generation of novel feed ingredients, which can serve as a significant raw material for biofuel production and a source of nutrients for animal feeding programs (Lum et al., 2013). Furthermore, various phytochemicals and functional nutrients present in microalgae make it a potentially attractive alternative to growth promoting antibiotics in animal feeds. The objective of this review is to describe industrial production, species, nutritional value, and data on the potential utilization of microalgae and microalgae products, specifically in diets for pigs.
There are thousands of different species of microalgae, which vary in nutritional composition. Examples of common microalgae species are Bacillariophyceae (part of phytoplankton), Clorophyseae (green algae), Cyanophyceae (blue green algae), and Chrysophyceae (golden algae). Spirulina maxima is one of the most consumed microalgae worldwide, due to its high protein content (approx. 60%) and to the fact that is fairly simple to extract and process (Van Iersel and Flammini, 2010). Crypthecodinium sp, are principally processed for their oils, which are extremely high in the omega-3 fatty-acid, Docosahexaenoic acid (DHA) (Van Iersel and Flammini, 2010). DHA is mainly found in brain and heart tissue, and is essential for both adult and infant cardiovascular and brain health, and also could have benefits in animal diets as well (Van Iersel and Flammini, 2010). The general nutritional characteristics of several species of microalgae are shown in table 1.
Table 1. Most common microalgae species nutritional comparison
|Microalgae species||Harvest-processing method||Crude protein (% dry matter)||Carbohydrates (% dry matter)||Lipids (% dry matter)||Reference|
|Anabaena cylindrica||Freshwater biomass-dried||43-56||25-30||4-7||Lum et al., 2013|
|Spirulina maxima||Cyanobacterium-single-cultivation||60-71||13-16||6-7||Lum et al., 2013|
|Chlorella vulgaris||Waste water collection, dried or oil extraction||51-58||12-17||14-22||Lum et al., 2013
Van Iersel and Flammini, 2010
|Staurosira sp.||De-fatted biomass, biofuel co-product||19||14-15||3-4||Austic et al, 2013|
|Crypthecodinium sp.||Glucose/acetic acid cultured, dried, oil extraction||12-15||40||40-50||Pleissner and Eriksen, 2012
Van Iersel and Flammini, 2010
A significant amount of microalgae are taken from freshwater environments and are processed using fermentation tanks, which have the capability of producing large quantities in short periods of time ("Innovation | Solazyme,"). Although, various species of microalgae do not require fermentation processes and are simply extracted from waste water; others, such as defatted microalgae, are derived from biofuel production systems. These differences, along with how each form of microalgae is utilized, can be seen in the graphic below.
Figure 2. Prediction of degradable fiber from concentration of total dietary fiber (Urriola et al. 2010)
From a nutritional standpoint, microalgae are applicable and attractive as a feed supplement to livestock diets. Various forms of microalgae that have been evaluated as feed supplements demonstrated crude protein levels ranging from 14-38.2%, which at its maximum level, is almost 4.5 times the amount of crude protein in various corn products (Lum et al., 2013). Microalgae products also exhibit elevated fat content, with ranges from 1.5-9.3%, and high levels of beneficial omega-3 fatty acids, vitamins, minerals, fibers and other bioactive compounds (Van Iersel and Flammini, 2010).
The University of Minnesota has evaluated nutrient content in microalgae can lead to diverse metabolic changes in mice as a model for other animals. For example, metabolomics analysis of biological samples from a mouse experiment showed that feeding a regular diet supplemented with microalgae increased the levels of intermediate metabolites in antioxidant defense, nucleotide biosynthesis, and anabolic metabolism (Ma et al., 2015). Levels of vitamin B have been shown to increase in mice as well with algae supplementation (Lee, 2014; Yang et al., 2011) . These data from the University of Minnesota suggests that feeding microalgae to pigs may help to increase antioxidant defense and anabolic metabolism (growth). Other types of microalgae have high levels of beta-glucans in their cell wall (Murphy et al., 2013). These beta-glucans have been proven to be beneficial for the gut microbiota of pigs (Murphy et al., 2013), especially in immature pigs that have yet to develop microflora within their gastrointestinal system, which is extremely important to overall health and growth.
These initial experiments at the University of Minnesota suggest that microalgae utilization in animal diets is promising. However, more information is necessary before widespread use of microalgae in animal feeding programs. The bioavailability and digestibility of nutrients and potential concentration of toxins are two aspects that require major research. The bioavailability of nutrients, such as amino acids need to be determined for accurate diet formulation for growing pigs. Therefore, new experiments that measure the digestibility of amino acids in microalgae sources and products, along with determining if toxins are present in significant quantities are required. With further research and experimentation, microalgae have the potential to change the sustainability of animal and food production systems all over the world. Their rapid growth and energy and nutrient density characteristics, along with their phytochemical properties have significant value for use in swine diets in the future. With a growing world population of people to feed, and a reduction in arable land, microalgae could provide a solution for a new age of alternative feed ingredients.
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