The gastrointestinal microbiota, which has been associated with nutrient availability and maintenance of the normal physiological status of the gastrointestinal tract, can be influenced by feeding effective prebiotic fibres. The prebiotic effects of unique seaweed blends have been demonstrated in trials, confirming positive impacts on the beneficial, butyrate-producing gastrointestinal microbiota.
Chief Commercial Officer
Ocean Harvest Technology
PREBIOTICS AND THE GI MICROBIOTA
The gastrointestinal (GI) microbiota can affect intestinal nutrient availability and modulate the immune response of the host animal (Stanley et al, 2014; LaBlanc et al 2017). The microbial community has a specific composition in healthy animals consuming a nutrient adequate diet (Borda-Molina et al, 2018); however, poor diet, stress, infection or other environmental challenges can alter the profile of the GI microbiota. This can result in the development of a condition referred to as dysbiosis, a disturbance of the normal GI microbiota profile resulting in an altered immune response and consequent digestive disorders (DeGruttola et al, 2016).
Recent advances in genomics have shed new light on the GI microbiota profile and related physiological effects. Using metagenomic analyses, chicken caecal samples were found to contain Proteobacteria as the most abundant phylum (47–79%) followed by Firmicutes (12–28%) and Bacteroidetes (7–27%). At the family level, the Ruminococcaceae, Lachnospiraceae, Clostridiaceae, Eubacteriaceae and ‘unclassified bacteria’ were the most abundant species (Borda-Molina et al, 2018).
Prebiotics are non-digested food components that can improve the gut health and digestive functions of the host animal. By definition, a prebiotic food component must be resistant to gastric acidity and hydrolysis by mammalian enzymes and subsequent gastrointestinal absorption, subject to fermentation by intestinal microflora and selectively stimulate the growth and/or activity of the intestinal bacteria that contribute to health and wellbeing of the host (Gibson and Roberfroid, 2017).
SEAWEED
Marine macroalgae consist of three groups, the Phaeophyta (brown), Chlorophyta (green) and Rhodophyta (red) seaweeds, with more than 10,000 species. Less than 300 of these species are commonly commercially used globally, with approximately 160 Rhodophyta, 75 Phaeophyta and 30 Chlorophyta exploited (White and Wilson, 2015). Seaweeds are known to be rich sources of bioactive compounds with potential applications in human and animal nutrition. Their biochemistry includes polysaccharides, peptides, essential fatty acids, phlorophenols, phytogens, pigments and minerals. Among the bioactive compounds in seaweed, the polysaccharides are of particular interest for their specific prebiotic effect on the gastrointestinal (GI) microbiota and reported health and nutrition benefits (Sardari and Karlsson, 2018; Cherry et al., 2019; Shannon et al., 2021).
SEAWEED POLYSACCHARIDES
Unique polysaccharides (dietary fibre) found only in seaweed account for around 30-75% of dry weight, serving a structural role in cell walls (Xu et al, 2017). Of the total fibre in seaweed, a proportion is soluble polysaccharides, possessing particular prebiotic activity. The soluble polysaccharides generally comprise around 55–65% of total fibre in commonly used green and red seaweed and can be even higher in commonly used brown seaweed (Lahaye 1991). These soluble polysaccharides are particularly effective prebiotics in animals (Hentati et al, 2020). Relative to fibres in land-based plants, seaweed polysaccharides tend to be more highly substituted, more complex and less lignified, making them attractive as functional prebiotics in the animal hindgut. In addition to solubility as a functional property, the sulphated seaweed polysaccharides are unique in that they combine the bioactivities of polysaccharides and the attached sulphate group. The fibres identified in seaweed are generally absent in land-based plants (Berri et al, 2017). The extent to which seaweed polysaccharides are sulphated differs among the main seaweed species. For example, the ulvans from green algae are extensively sulphated, whereas alginates and agars, the predominant polysaccharides in brown and red seaweed, respectively, are not. The high diversity in seaweed polysaccharides provides opportunities to combine different seaweed species, creating a more diverse source of prebiotic fibres compared to using a single seaweed or land plant polysaccharide as a source of prebiotic fibre. This concept has been used to formulate specific blends of seaweeds, containing varying proportions of brown, green and red seaweeds.
The bioactivity of seaweed polysaccharides depends on factors such as molecular weight, charge density, sulphate content and structural and conformation characteristics (Hentati et al., 2020). Numerous scientific papers indicate that seaweed polysaccharides may display bioactive properties including anticoagulant, antioxidant, antithrombotic, bacteriostatic and antiviral activities. Several studies have reported that sulphated polysaccharides extracted from different seaweeds have demonstrated an inhibitory effect on the growth of pathogenic bacteria (De Jesus Raposo et al 2015). Extracts rich in seaweed fibres decreased the faecal E. coli populations in pigs and reduced bacterial load in raw meat products (McDonnel et al, 2010). Furthermore, green seaweed polysaccharides such as ulvans have been shown to possess strong immune-modulating activities (Wany et al., 2014). However, evidence suggests the prebiotic effect is the primary mode of action by which macroalgal polysaccharides added to animal feed influences GI microbial profile, physiological indicators of GI health, digestive efficiency and growth response in animals.
APPLYING A SEAWEED BLEND POSITIVELY IMPACTS POULTRY GI MICROBIOTA
In a 42-day study, OceanFeed™ Poultry, a proprietary blend of brown, green and red seaweeds, included in broiler diets moved the relative abundance profile of bacterial families in the caeca towards Firmicutes, with a decrease in Actinobacteria (Figure 1). This shift led to a change in Firmicutes: Bacteroidetes ratio from 17.7 to 22.6 (Mohammadigheisar et al, 2020), indicating the presence of more of the important fibre-degrading, butyrate producers such as the Ruminococcaceae and Lachnospiraceae (Vital et al, 2017). Similar changes have also been observed in the faecal microbiome of pigs and horses when fed suitable seaweed blends (Sands et al, 2022). In this trial, the broiler chickens consuming the seaweed-containing diet tended (P≤0.09) to have improved body weight gain and feed conversion ratio.
In a follow-up trial, broilers were again fed from 1-42 days of age with diets without (control) or supplemented with OceanFeed™ Poultry seaweed blend. Liveweight at 42 days increased by 50 grams while Feed Conversion Ratio improved (P<0.01) by 4-points with the addition of OceanFeed™ Poultry (Figure 2). Mortality was reduced from 4% to zero, while the European Productivity Index (EPI), calculated from liveweight, FCR and liveability, also improved (P<0.01) with the addition of OceanFeed™ Poultry. Overall, OceanFeed™ Poultry reduced total feeding costs (including seaweed) per kg liveweight gain.
The effect of OceanFeed™ Poultry seaweed blend on layer performance was subsequently tested in a 12-week trial with 50-62 week old hens. OceanFeed™ improved (P<0.05) hen day production by 2.5% and feed conversion ratio by 4 points (Figure 3). Egg quality was also improved (P<0.05), with an increase in Shell Breaking Strength of 0.3 kg.F and in Haugh Units of 2.8.
CONCLUSIONS
The GI microbiota, which has been associated with nutrient availability and maintenance of the normal physiological status of the GI tract, can be influenced by feeding effective prebiotic fibres. The prebiotic effects of unique seaweed blends have been demonstrated in trials, confirming positive impacts on the beneficial, butyrate-producing GI microbiota. Butyrate serves a key role in energy provision to the intestinal epithelium, modulating immune response, and affects several key metabolic pathways in the body. Two trials reported here confirm the ability of seaweed supplementation to improve performance and reduce production costs in broilers and layers.
About Hadden Graham
Dr Hadden Graham is Chief Commercial Officer at Ocean Harvest Technology, having previously worked for 3 decades in the feed additives industry, primarily with feed enzymes. He served as President of the EU Association of Specialty Feed Ingredients and their Mixtures (FEFANA) from 2007-09.
