Intersection of the Nutritive Value and Bioactive Potential of Two Emerging Classes of Novel Feed Ingredients: Insect and Algae Products

Introduction

Monogastric feeds are reliant on plant-based protein sources, like corn and soybean. However, increasing demands on these plant-based materials for non-food industries, such as biofuels, is also associated with an increase in the price of these feed ingredients, placing an impetus on the demand for these alternative protein sources (Leiber et al., 2017). Emerging areas of monogastric animal nutrition research include the use of insect meal, microalgae, single cell proteins and fermentation products as alternative feed sources (Aas et al., 2022).

The use of these novel feed ingredients originating from insects and algae as protein and lipid sources in monogastric diets continues to gain interest. Many of these feed ingredients display an efficient nutritional profile for use in monogastric feeds, in addition to possessing additional bioactive properties and promise in terms of sustainability and feed security. Many of these products have yet to be approved as regulated feed ingredients, or have only recently been approved by regulating bodies, such as the Canadian Food Inspection Agency (CFIA). As an example, at present, only one dried microalgae product, three black soldier fly larvae product (one meal and two oils) and a single earthworm lysate extract are the only monogastric-approved feed ingredients of note in these two categories listed on CFIA’s Schedule IV and V List of Approved Ingredients in the Feed Regulations. (CFIA, 2021). Additionally, the dietary inclusion level of whole black soldier fly larvae meal is currently limited to a maximum dietary inclusion level of 7.5 and 10% in tilapia and salmonids, respectively, the defatted larvae meal is limited to 10% in these same fish and the oil is limited to a maximum dietary inclusion level of 5% in poultry and fish (CFIA, 2021).

For companies to produce and sell similar feed sources for use in Canada, adequate data is required for their regulatory approval, which includes production data, with focus on nutrient digestibility and performance (growth, egg production) of animals fed these feed ingredients. Secondary research in novel feed ingredients involves research into their sustainability and impacts of additional bioactive compounds (or extracts) on animal production and health. The findings from this research are helping to contribute to our understanding of the potential use of these products in animal feeds. It may be detrimental to treat these feed ingredients like plant or animal products, leading to confusing results when the additional properties present in these novel feed ingredients are not considered.

Literature review and discussion

Insect product use in monogastric animal feeds

Many insects (black soldier fly, cricket, mealworm) possess an acceptable nutritional profile for use in monogastric feeds including adequate amino acid profiles in addition to other potential nutrients and bioactive compounds (Biasato et al., 2017; Leiber et al., 2017; Bovera et al., 2016; Cullere et al., 2016; De Marco et al., 2015; Khusro et al., 2012; Velten et al., 2016; NRC, 1993). The insect kingdom is vast, thus nutritional variation among species, as well as for life stages within species, should be expected. Some of the more commonly explored species for use in animal feeds have a nutrient profile that does not replicate, but can be considered comparable to that of corn and soybeans (Khusro et al., 2012; Liu et al., 2017).

Additional information on individual insect species and their nutritional impact, when included in animal feeds, will be valuable, as the current depth of knowledge is limited, but promising. Much of the nutritional evidence involving these feed ingredients suggest minimal disturbances in production performance at reasonable dietary inclusion levels (Fisher et al., 2020; Bovera et al., 2016; Cullere et al., 2016). The presence of antimicrobial peptides in insect products are also interesting, particularly in antibiotic-free animal production, as they may protect against pathogenic microbial organisms responsible for intestinal disturbances that impair health, immune function and production performance (Biasato et al., 2017; Józefiak et al., 2016; Chernysh et al., 2015; Yi et al., 2014).

Use of algaes in monogastric animal feeds

Numerous opportunities exist to include algaes (macro and micro) in monogastric diets. The benefits of microalgae is attractive to many industries beyond the feed industry, including biofuel applications, flavor enhancers/feed attractants and sources of nutrients in human nutrition (proteins/amino acids, vitamins, polysaccharides and lipids/long-chain fatty acids) (Pignolet et al., 2013; Becker, 2007; Spolaore et al., 2006; Brown, 1991).

In the animal feed and human food industries, functional compounds, such as bioactive peptides derived from microalgae are also attracting attention due to evidence that these peptides exhibit positive impacts on immune function and physiological regulation (Suetsuna et al., 2004; Morris et al., 2007; Sheih et al., 2009). Macroalgae contains additional bioactive properties, including antioxidant and antimicrobial compounds with the potential to maintain or improve the function of the intestinal barrier (Tresserra-Rimbau et al., 2018; Abdel-Moneim et al., 2020; Ford, et al., 2020; Zhong et al., 2014). Microalgae-derived, sustainable sources of n-3 HUFAs also show promise for future-focused sustainability goals (Tocher, 2015), as this source of fatty acids will provide necessary nutrients to the industry without impacting wild fish stocks.

Allelochemicals in feed ingredients

Many non-animal-based feed ingredients produce and possess chemical compounds responsible for physiological functions and protective defense that will affect the growth, survival and/or reproduction of other organisms, which is referred to as allelopathy. The effect of these allelochemicals on the organism involved may be beneficial (positive allelopathy) or harmful (negative allelopathy) (Zhao et al., 2022; Mendes and Vermelho, 2013). Some of these compounds carry through feed processing and remain in the “as fed” animal feed.

In traditional monogastric nutrition, allelochemicals are commonly observed in plant-based feed ingredients as antinutrients (negative allelochemicals) and bioactives (positive allelochemicals), some of which are reduced, neutralized or removed through formulation and processing techniques. A short list of antinutrients in plant-based feed ingredients includes tannins, alkaloids, terpenes (such as saponins), glucosinolates, cyanogens, fibres, mucilage, isoflavones lectins and haemagluttanins (Collins et al., 2013; Htoo et al., 2008; Francis et al., 2001). The level of presence of each antinutrient, degree of severity of the effect of feeding these ingredients varies by plant species, as well as the species to which they are fed. For example, a carnivorous fish, such as a salmonid will be more sensitive to some fibrous components of the diet than an herbivorous / selectively omnivorous animal, such as a chicken or pig.

Allelochemicals in insects

The most-commonly referenced allelochemical in insects is located in their exoskeleton. Insect exoskeleton contains chitin, which can be subdivided further to a compound with antimicrobial properties: chitosan. Chitosan is also present in shrimp shells and fungi and is suggested to play a role in food allergies, but in the case of insect-based feed ingredients, has not been definitively tested and confirmed. Because of the antimicrobial properties of chitin/chitosan, research is currently underway on this compound in the hopes of large-scale application of this compound in antibiotic-free poultry production (Marono et al., 2017; Józefiak et al., 2016).

In feeding studies involving the inclusion of insects and insect products in animal feeds, reduced production performance observations in animals fed a test diet containing insect products vs animals fed a control diet is often attributed to chitin (Mwaniki et al., 2020; Kawasaki et al., 2019; Bovera et al., 2016; Makkar et al., 2014). However, in these studies, chitin and/or chitosan is rarely measured in order to compare feeding dose with animal response. Due to a dearth of quantified data, there is not enough scientific evidence available in the literature to definitively attribute reduced production performance in animals fed insect products to chitin or at the least, solely to chitin.

In addition to chitin, insects contain a number of self-protective compounds with allelopathic properties, including toxic cyanides and deterrent alkaloids, ketones, aldehydes and terpenes (Boevé and Giot, 2021; Zagrobelny et al., 2018), many of which are known to impair nutrient digestion, reduce feed intake and/or animal growth when present as antinutrients in plant-based feed ingredients (Collins et al., 2013; Francis et al., 2001). Although evidence of these allelochemicals in insects have been identified, the effects of the presence of these compounds in insect-based feed ingredients used in animal diets and the conditions required to reduce, remove or neutralize these allelochemicals have yet to be determined.

Allelochemicals in algaes

Marine microalgaes maintain protective defensive functions against environmental pressure through allelopathy. Allopathic functions in marine microalgae may involve inhibition of predatory protozoans through the inhibition of ciliate population growth and density (Zhou et al., 2022) to the use of phagotrophy and osmotrophy to ingest prey and organic molecules, respectively, in microalgae present in zooplankton (Mendes and Vermelho, 2013), and defensive responses to antibiotics, such as tetracycline and microalgae-bacterial granules (Wang et al., 2020).

Major compounds of interest in macroalgaes include non-starch polysaccharides, such as phlorotannins (tannins) and polyphenolic compounds, such as alginates and fucoidans (Naiel et al., 2021; Leyton et al., 2016; Fleming, 1995). Depending on dose and application, the positive and negative allelopathic properties of these compounds may be considered interchangeably.

In industries unrelated to animal agriculture, the allelochemicals produced by marine algaes also have application as biological herbicides and pesticides, which should be considered when analyzing production-based data in animals fed marine microalgaes in their diets. Many of the allelochemicals produced by microalgaes as a protective mechanism are similar to those found in plants that have know negative impacts on the nutritive value of animal feeds, such as lactones, aldehydes, phenolic compounds, alkaloids, oligopeptides and cyclic peptides. Additional allelochemicals produced by marine microalgaes are enzyme inhibitors, which may impair nutrient digestion, including glucosidase, glycosidase, peptidase and alpha-amylase inhibitors(Mendes and Vermelho, 2013).

Conclusion

Insect meals and algae protein products are up-and-coming ingredients in the monogastric feed industry. These innovative feed production approaches have the capability to utilize minimal space, redirect waste nutrients and lead the way for regenerative agricultural approaches in animal agriculture. Their many beneficial properties have the potential to play a role in ensuring an affordable, sustainable food supply for future generations.

When assessing the nutritional value of insects and algaes, limitations on maximum ingredient inclusion levels are too often held at face value, attributing reduced animal production performance in animals fed insects to chitin and performance reductions in animals fed algae to the rigid hemicellulose-supported structure of its cell wall (Becker, 2007). Although these components may provide barriers, algaes in particular have had a generous deal of research and development devoted to disrupting the cell wall, including cell lysis, ultrasound, thermal and osmotic shock (Ursu et al., 2014; Sari et al., 2013; Doucha and Lívanský, 2008; Middelberg, 1995; Hopkins, 1991), overcoming any challenges it may pose to an animal’s ability to access the nutrients within. To truly understand a feed ingredient, one must thoroughly see all aspects of its composition, capabilities and obstacles to overcome.

Novel feed ingredients such as insect and algae oil and protein products, as well as additionally processed feed additives, including lysates, offer numerous benefits beyond the plant and animal-based feed ingredients commonly included in monogastric diets. As with plant-based feed ingredients, optimal formulation and processing techniques will add nutritive power to insect and algae-based feed ingredients, by evaluating these ingredients for their nutritional and allelochemical profiles and utilizing this knowledge to maximize their benefits and minimize detrimental impacts.

Adopting the approaches used in developing value-added plant-based feed ingredients, but not duplicating these processes will allow nutritionists to treat algaes like algaes and insects like insects, rather than seeing them as plant- and animal-adjacent feed ingredients. This strategy will inform future directions in processing, formulation and maximum dietary inclusion in this emerging era of the feed industry.

Presented at the 2022 Animal Nutrition Conference of Canada. For information on the next edition, click here.