ISSUE FOCUS 34 FEED & ADDITIVE MAGAZINE January 2023 ti-inflammatory (Lomartire and Gonçalves, 2022). The prebiotic effects of the seaweed polysaccharides are potentially of greatest interest, due to their impact on the GI microbiota and subsequent health and nutrition benefits (Sardari and Karlsson, 2018; Cherry et al., 2019; Shannon et al., 2021). SEAWEED POLYSACCHARIDES The polysaccharide content of seaweeds is typically in the range of 30-75% of dry matter. An important aspect of seaweed polysaccharides (fibre) is their highly soluble nature, 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). These soluble polysaccharides differ in their structure to terrestrial plants, as they tend to be more highly substituted, more complex and less lignified. They 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; 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) and immunomodulatory effects (Wany et al., 2014). 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). Some bioactive properties of interest include anti-pathogenic, anticoagulant, antioxidant, antithrombotic, and antiviral activity. In terms of the current status of research in the animal nutrition field, evidence suggests the prebiotic effect is the primary mode of action by which macroalgal polysaccharides added to animal feed influence the GI microbial profile, with subsequent beneficial effects on gut health, growth rates and feed efficiency. The high diversity in the functional properties of 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. APPLYING A SEAWEED BLEND POSITIVELY IMPACTS PIGLET GI MICROBIOTA In a 35-day US study with piglets initially weighing approximately 5 kg, OceanFeed™ Swine, a proprietary blend of brown, green and red seaweeds, included in diets with lower zinc oxide (ZnO, phases 1 & 2) and copper (Cu, phase 3) influenced the relative abundance profile of bacterial families in the faeces (Figure 1). This included an increase in the relative abundance of the important fibre-degrading, butyrate producing Ruminococcaceae and Lachnospiraceae (Vital et al, 2017) from 14% to 24% (P<0.05). The diversity of the microbiome, measured as the Shannon entropy, was increased from 4.43 to 6.48 (P<0.01) in the presence of OceanFeed™ (Figure 2), while the Firmicutes:Bacteroidetes ratio also increased from 1.08 to 3.62 (P<0.05), indicating a healthier gut (Mohammadigheisar et al, 2020). Figure 1. Relative abundance of faecal bacteria (>1% total) at phylum level in piglets consuming control diets or with added OceanFeed™ Swine seaweed blend.
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