Marine macroalgae, more commonly known as seaweed, are an area of growing interest for animal nutritionists globally, due to their range of bioactive components such as minerals, vitamins, polysaccharides, proteins, lipids, pigments and polyphenols (Kumar et al., 2008). With the sustainability of livestock production coming under increasing scrutiny, the use of seaweeds in animal nutrition provides a unique opportunity to enhance the sustainability of both the feed itself, and the animal protein produced following consumption of the feed.
Technical Director
Ocean Harvest Technology
There is an extensive body of scientific research demonstrating the functional compounds present in macroalgae, or seaweed. A number of studies have identified the prebiotic effects of soluble and sulphated polysaccharides in seaweed, and their beneficial effects on gut health and animal performance. Ongoing research is investigating additional bioactivity of seaweed, particularly the antioxidative, anti-inflammatory, antimicrobial and immunomodulatory effects.
A SUSTAINABLE SOURCE OF BIOACTIVE COMPOUNDS FOR ANIMAL FEEDS
Marine macroalgae, more commonly known as seaweed, are an area of growing interest for animal nutritionists globally, due to their range of bioactive components such as minerals, vitamins, polysaccharides, proteins, lipids, pigments and polyphenols (Kumar et al., 2008). With the sustainability of livestock production coming under increasing scrutiny, the use of seaweeds in animal nutrition provides a unique opportunity to enhance the sustainability of both the feed itself, and the animal protein produced following consumption of the feed. The absence of a requirement for fresh water, land use or fertiliser in the production of seaweed compares very favourably to the production of terrestrial-based feed ingredients (Duarte et al., 2017). This is particularly the case in instances where wild seaweed is harvested from invasive blooms, effectively recycling nutrient run-off from agricultural operations on land. There are more than 10,000 known species of macroalgae, classified into 3 groups according to their pigmentation. The Phaeophyta (brown), Chlorophyta (green) and Rhodophyta (red) differ in their chemical and nutrient composition (Morais et al., 2020), providing a significant opportunity to combine species from the different groups to achieve a balanced blend of bioactives for animal feed.
BIOACTIVITY OF SEAWEEDS
A large body of evidence exists in scientific literature to indicate a central role of polysaccharides in the bioactivity of marine macroalgae (Lomartire and Gonçalves, 2022), with properties such as anti-inflammatory, antioxidant, antimicrobial, anticarcinogenic and immune-modulating functions all attributed to seaweed polysaccharides and their derivatives (Xie et al., 2023). There is also strong evidence to demonstrate the prebiotic effects of seaweed polysaccharides on the GI microbiota, with subsequent beneficial effects on nutrition and health (Sardari and Karlsson, 2018; Cherry et al., 2019; Shannon et al., 2021).
Polysaccharides typically comprise of 30-75% of the dry matter of macroalgae, with 55-65% of total polysaccharides in Green and Red Seaweeds in the form of soluble fibre, and even higher content found in the Ascophyllum and Laminaria species of Brown seaweeds (Lahaye, 1991). The soluble nature of these polysaccharides is an important characteristic, as is their ability to resist gastric acidity, digestive enzymes and GI absorption, making them attractive as functional prebiotics in the animal hindgut (O’Sullivan et al., 2010, Hentati et al., 2020).
Another characteristic that differentiates some seaweed polysaccharides from those found in land-based plants is their sulphated nature, and these sulphated polysaccharides have been shown to have additional bioactivity, such as inhibition of pathogenic bacteria (De Jesus Raposo et al., 2015, McDonnell et al., 2010). Recent in vitro trial work carried out by Ocean Harvest Technology investigated this point further, in a study designed to elucidate the mode of action of their seaweed blends in supporting animal health and performance. The objective of this study was to assess the potential for OceanFeed™ seaweed blend to bind two common pathogens (Clostridium perfringens and Escherichia coli) and form agglomerates. The binding efficacy of OceanFeed™ was compared with a negative control, and with a positive control (a commercial yeast cell wall product commonly used in animal diets as a pathogen binder). Pathogen binding capacity was assessed at pH 6.5 (neutral, representing the small intestine) and pH 2.5 (acidic, representing stomach conditions).
OceanFeed™ enhanced pathogen agglomeration of both C. perfringens and E. coli compared with both the negative and positive controls. This effect was observed in a dose-dependent manner up to a maximum of 60% and 42% agglomeration of C. perfringens and E. coli, respectively (Figure 1). The positive control did not demonstrate any clear agglutination capacity for either pathogen tested.
THE USE OF SEAWEED IN ANIMAL NUTRITION
The majority of cultivated and harvested seaweed is currently used in the food and hydrocolloid industries, with just under 4% used in the animal feed industry (Xie et al., 2023). The dietary fibre and phytochemical composition of macroalgae present a clear opportunity for growth in this sector, utilising a sustainable resource to enhance animal performance and health. Due to bioaccumulation of heavy metals, seaweeds should be utilised at an additive/supplement level in animal feed, rather than as a substitute for traditional terrestrial macro ingredients. In order to accelerate the adoption of a relatively new technology in animal feed, research is required to demonstrate the applications, benefits and economic returns for producers when supplement seaweed.
APPLYING A SEAWEED BLEND IMPROVES GROWTH PERFORMANCE AND SURVIVAL OF SHRIMP
In a study conducted in Thailand with juvenile white shrimp, OceanFeed™ Aqua (OFA) a proprietary blend of red, green and brown macroalgae, significantly (P<0.05) improved tank yield and feed conversion efficiency, resulting in an 11% increase in shrimp yield at the end of the 8-week trial period (Figure 2).
As part of the same study, a separate group of juvenile white shrimp were supplemented with OFA for 3 weeks, then were challenged with the severe pathogenic bacteria Vibrio parahemolyticus EMS strain at 106 CFU/ml for 15 days. At the end of the challenge period the group fed OceanFeed™ Aqua had a survival rate of 60%, significantly higher than the control group of 42% (Figure 3), suggesting either a direct effect of the macroalgae blend on the pathogen, or an immunomodulatory effect in shrimp.
SEAWEED BLENDS IMPROVE EGG PRODUCTION AND FEED EFFICIENCY IN LAYING HENS
Macroalgae blends have previously been shown to influence the GI microbiota of broilers, increasing the Firmicutes to Bacteroidetes ratio in the ceca, enhancing the abundance of the fibre degrading, butyrate producing bacteria, and ultimately improving feed efficiency and weight gain (Sands, 2022). In a recent study in early-lay white Hyline hens, birds were fed either a control diet, or a control diet supplemented with a blend of red, green and brown macroalgae (OceanFeed™ Poultry), from week 12-29 of age. OceanFeed™ Poultry significantly improved hen-day egg production percentage, egg weight and feed conversion rate (from weeks 26 to 29 inclusive), compared with the control diet (Figure 4).
SEAWEED BLENDS ARE A COST-EFFECTIVE ALTERNATIVE TO CONVENTIONAL GUT-HEALTH ADDITIVES
Previous research has demonstrated the potential for macroalgae blends to replace both antibiotic growth promoters and therapeutic levels of zinc oxide in the diet of nursery pigs, with improvements in gut health and performance mediated by the beneficial effects of the seaweed polysaccharides on the diversity and abundance of key bacterial populations in the GI tract (Sands, 2022; Hutchinson 2023). Due to societal concerns, regulators in a number of markets around the world have banned the use of antibiotics and medicinal zinc oxide in swine diets. In such markets, producers have turned to a range of feed additives designed to support gut health, such as phytogenics, pre- and probiotics, organic acids and yeast products. The wide range of bioactive properties in seaweed provide solid justification for the use of seaweed blends as an alternative to these traditional gut health additives.
In a trial in nursery pigs in Spain, the performance and production economics of two groups of pigs fed different dietary treatments was compared in the nursery phase. In one group, the positive control, pigs were fed a standard diet plus a combination of traditional gut health additives designed to support gut health. These additives included butyrate, yeasts, organic acids, mycotoxin binders and phytogenics. The second group was fed the standard diet, with none of the above gut health additives, but with a blend of red, green and brown seaweed (OceanFeed™ Swine; OFS). Feed intake, average daily gain and feed conversion were not significantly different between the treatment groups, but were numerically improved in pigs supplemented with OFS. Faecal scores were significantly improved by OFS supplementation (from 2.10 to 1.72, where 0 is good and 5 is poor), indicating improved gut health in this group of pigs. The numerical improvements in weight gain and feed conversion ratio, combined with a lower feed cost for the OFS-supplemented group, resulted in a tendency (P=0.07) towards lower feed costs per kg gain in the pigs consuming diets supplemented with OFS, compared to those consuming the traditional gut health additive diet.
CONCLUSIONS
There is growing interest in the use of seaweed in animal nutrition, with an extensive body of scientific research demonstrating the functional compounds present in macroalgae, their bioactivity, and potential applications in animal feed. The production of seaweed, and in particular the wild harvesting of algal blooms, presents a valuable opportunity for the animal nutrition industry to enhance the sustainability of feed production, in conjunction with realising the benefits of macroalgal supplementation on animal health and performance. To date, a number of studies have identified the prebiotic effects of soluble and sulphated polysaccharides as a key mode of action of seaweed products, enhancing the diversity of the gut microbiome and the abundance of butyrate-producing bacteria in a number of animal species. Ongoing research is investigating additional bioactivity of polysaccharides and other functional macroalgae components, with potential to exploit the reported antioxidative, anti-inflammatory, antimicrobial and immunomodulatory effects of different seaweed species. Commercial trials have been conducted that demonstrate the improvements in animal health and performance across species and applications, showing the economic benefits of using seaweed supplements. Taken together, the scientific research and commercial studies indicate a vital role for functional seaweed supplements in a sustainable future for the animal nutrition industry.
About Ian Hutchinson
Dr Ian Hutchinson is Technical Director at Ocean Harvest Technology, having previously worked for 9 years in the feed additives and premix industry. In his role as Technical Director, Ian is responsible for developing and driving the Ocean Harvest Technology’s research and development agenda as well as customer technical support and product trials.
