Intensive swine production systems have, for many years, utilised in-feed antibiotics and therapeutic levels of zinc oxide to support gastrointestinal health and animal performance. As the industry moves away from this practice, it has become apparent that the microbiome can be positively influenced by feeding effective prebiotic fibres, leading to improvements in nutrient availability and maintenance of the normal physiological status of the gastrointestinal tract. The prebiotic effects of unique seaweed blends have been demonstrated in trials…
Technical Director
Ocean Harvest Technology
In the absence of in-feed antibiotics and therapeutic levels of zinc oxide, gastrointestinal health and physiological performance can be maintained by feeding effective prebiotic fibres. The prebiotic effects of unique seaweed blends have been demonstrated in trials with a number of animal species, confirming positive impacts on microbial diversity and on the abundance of beneficial, butyrate-producing gastrointestinal microbiota.
GUT HEALTH AND THE MICROBIOME
A healthy gastrointestinal (GI) tract is essential for effective nutrient metabolism, animal health and production efficiency in production animals. The gut microbiota is a key component of intestinal health, aiding nutrient absorption and regulating gut barrier function and intestinal immune function, with subsequent benefits for production and feed efficiency (Gardiner et al., 2020). The microbiome’s effect on gut health is mediated both by direct interaction with mucosal epithelial cells or indirectly via the production of metabolites such as short-chain fatty acids (SCFAs), secondary bile acids, polyamines and phenols (Vasquez et al., 2022).
A healthy GI microbiota is diverse, stable, and relatively resilient. Severe stressors, however, can unfavourably impact the microbial profile of the gut, leading to a condition known as dysbiosis, a disturbance of the normal GI microbial profile. These stressors include nutritional deficiencies, diseases and infections, and environmental challenges. Dysbiosis is associated with suppressed immune function and an increased risk of disease (DeGruttola et al, 2016), and is a leading cause of post-weaning diarrhoea in piglets (Gresse et al, 2017).
Recent advancements in both DNA sequencing technology and powerful bio-informatic analyses have facilitated greater understanding of the composition of the GI microbiota, and its impact on the host animal. The dominant phyla in the pig’s caecum are the Firmicutes and Bacteroidetes, which account for more than 80% of the identified bacterial sequences identified. The most abundant bacterial families in the pig’s caecum and colon were Prevotellaceae (22.3%), Lactobacillaceae (17.9%), Lachnospiraceae (8.9%), Clostridiaceae (5.8%), Bacteroidaceae (5.4%), Veillonellaceae (5.4%) and Ruminococcaceae (3.7%), as reported by Tröscher-Mußotter et al, (2019).
PREBIOTICS
A prebiotic is defined as “a selectively fermented ingredient that results in specific changes in the composition and/or activity of gastrointestinal microbiota, thus conferring benefit(s) on host health” (Gibson et al., 2010). Prebiotic food components 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). With regulatory and societal pressures leading to the removal of in-feed antibiotics and therapeutic levels of zinc oxide from diets in animal nutrition industries around the world, the use of prebiotics to confer positive effects on GI health through the modulation of the gut microbiome presents a valuable opportunity for farmers to sustainably enhance animal health and production efficiencies.
SEAWEED
Seaweeds, or marine macroalgae, have long been of interest for human and animal nutrition, due to their range of bioactive components such as minerals, vitamins, polysaccharides, proteins, lipids, pigments, carotenoids and polyphenols (Kumar et al., 2008). Macroalgae can be divided into 3 main groups, based on their pigmentation:
• Phaeophyta (brown); for example Ascophyllum, Laminaria
• Chlorophyta (green); for example Ulva, Cladophora
• Rhodophyta (red); for example Chondrus, Gracilaria
Collectively there are over 10,000 known species of macroalgae, although less than 300 of these species are commonly commercially used (White and Wilson, 2015).
The compounds present in seaweed possess a number of biological properties with beneficial activities for both human and animal health, including antimicrobial, antioxidant, antiviral and anti-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). Similar changes have also been observed in the microbiome of chickens and horses when fed suitable seaweed blends (Sands et al, 2022).
The beneficial impacts on the GI microbiome of the piglets in this trial were reflected in physiological performance improvements, as the piglets consuming the seaweed-containing diets tended to have improved feed intake and body weight gain, despite the reduced ZnO and Cu contents of the diets (Figure 2).
A trial in an Asia-Pacific university facility looked at the effect on performance of adding either sub-therapeutic antibiotic growth promoters or OceanFeed™ Swine seaweed blend to standard diets fed to piglets weaned at 28 days of age (~10 kg LW). Over the 24-day trial, both the antibiotic growth promoters and OceanFeed™ improved (P<0.05) daily gain and thus final liveweight (Table 1). Both also improved the visual diarrhoea index (P<0.05), indicating that the seaweed blend, by influencing the gut microbiome, can improve gut health and piglet performance.
In a subsequent commercial North American trial, close to 1,000 piglets (21 day old, ~ 6 kg LW) were fed on either control diets including in-feed antibiotics and ZnO or test diets free from antibiotics and ZnO but supplemented with OceanFeed™ Swine seaweed blend. Over the 7-week trial both feed intake and daily gain were higher (P<0.05) with the OceanFeed™ supplemented diets (Table 2), with final weight improved (P<0.05) by almost 700 g, despite the lack of dietary antibiotics and ZnO.
In a follow-up trial by the same North American commercial company, approximately 1,000 piglets (21-day weaning age, at ~ 7 kg initial LW) were again fed on either control diets including in-feed antibiotics and ZnO or test diets free from antibiotics and ZnO but supplemented with OceanFeed™ Swine seaweed blend. Over the 7-week trial neither feed intake nor daily gain were affected by removal of the dietary antibiotics and ZnO (Figure 3). However, visual diarrhoea score was improved from 4.9 to 3.6 and mortalities and removals were reduced from 2.2% to 1.3% with OceanFeed™. Both these trials indicate that, under commercial production conditions, appropriate seaweed blends can positively influence gut stability and help allow antibiotic growth promoters to be replaced without losing piglet performance.
CONCLUSIONS
Intensive swine production systems have, for many years, utilised in-feed antibiotics and therapeutic levels of zinc oxide to support GI health and animal performance. As the industry moves away from this practice, it has become apparent that the microbiome can be positively influenced by feeding effective prebiotic fibres, leading to improvements in nutrient availability and maintenance of the normal physiological status of the GI tract. 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. The trials reported here, including two under commercial conditions, confirm the ability of seaweed supplementation to improve performance and help replace antibiotic growth promoters in piglet production.
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. Inv his role as Technical Director, Ian is responsible for developing and driving Ocean Harvest Technology’s research and development agenda as well as customer technical support and product trials.
