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Seaweed as a Premium Natural Prebiotic for Dogs
By Dr Jason Sands; Head of Nutrition, Ocean Harvest Technology
Marine macroalgae consist of three diverse Phyla, the Phaeophyta (brown) Chlorophyta (green) and Rodophyta (red) seaweeds. Numerous published reports and decades of successful use have highlighted the potential of seaweeds as rich sources of bioactive compounds with potential applications in animal nutrition. Among the bioactive compounds highlighted in seaweed, the polysaccharides are of particular interest for their specific prebiotic effects on the gastrointestinal (GI) microbiota (de Jesus Raposo et al 2016; Sardari and Karlsson, 2018; Cherry et al., 2019; Shannon et al., 2021).
The GI microbiota has been shown to affect the availability of nutrients in the intestine, the immune response and to provide signals that effect behaviour of the host (Schmitz and Suchodolski, 2016). Under normal diet and health conditions the microbial community has a specific composition. Poor diet, stress, infection, or other environmental changes can alter the normal profile of the GI microbiota.
Prebiotics are defined as non-digested food components that, through the stimulation of growth and/or activity of a single type or category of microorganisms residing in the GI tract, improve the health status of the host animal (Gibson and Roberfroid, 1995). To be considered a prebiotic the food component must: 1) be resistant to gastric acidity and hydrolysis by mammalian enzymes and subsequent gastrointestinal absorption; 2) be subject to fermentation by intestinal microflora; and 3) selectively stimulate the growth and/or activity of the intestinal bacteria that contribute to the health and well-being of the host.
Unique polysaccharides, complex carbohydrate polymers or fibre found only in macroalgae, account for around 30-75% of the dry weight of seaweeds, where they serve in a structural role in cell walls (Xu et al, 2017). Green, red, and brown algae contain a significant proportion of sulfated polysaccharides generally not found in land-based plants (Berri et al, 2017). Soluble polysaccharides comprise around 50–55 % of total fibre in commonly used green and red macroalgae and 65–85 % in brown macroalgae (Lahaye 1991). These soluble polysaccharides are particularly effective prebiotics in animals (Hentati et al., 2020). Seaweed Polysaccharide Diversity
Seaweeds contain many different polysaccharides, with similar contents of total carbohydrates in brown and green seaweeds, whereas red seaweeds tend to be slightly lower. In addition to solubility as a functional property, sulfated polysaccharides (SP) of seaweed origin are unique in that they combine the bioactivities of polysaccharides with the additional bioactivity of the attached sulfate group. The extent to which seaweed polysaccharides are sulphated differs among the main seaweed families. For example, the ulvans from green algae are extensively sulphated, whereas alginates, the predominant polysaccharide in brown seaweed, are not sulphated. The diversity of seaweed polysaccharides indicates that a combination of seaweeds would provide a more diverse source of prebiotic activity compared to using a single seaweed as a feed supplement.
Recent advances in genomics techniques have shed new light on the prebiotic effect of seaweed polysaccharides on the GI microbiota profile and related physiological effects (Schmitz and Suchodolski, 2016). For example, the Firmicutes phyla account for around 30% of the colonic and faecal microbiome in healthy dogs (Suchodolski et al. 2008). The order Clostridiales were found to be around 18% of the bacterial sequences, with Clostridium cluster XIVa accounting for around 50%. It is interesting to note that Clostridium cluster XIVa includes Eubacterium, Roseburia and Ruminococcus spp., some of the important fermenters of dietary fibre in the hindgut. Alterations in the profile of the microbiota is a key factor in the development of acute or chronic GI disease (Schmitz and Suchodolski, 2016). Studies show
that dogs with acute diarrhoea had increased Clostridia perfringens, Eschericia coli, Lactobacillus and Enterococcus spp. and reduced abundance of groups such as Faecalibacterium, Ruminococaceae and Blautia spp. that make up the normal colonic microbiota. In addition, the sulphated ulvans and their oligosaccharides in the green seaweed Ulva spp. are known to possess strong immune-modulating activities (reviewed by Wany et al., 2014).
Practical applications of Seaweed prebiotics in dogs
Reducing Mouth Odour
Mouth odours can indicate several health conditions, one of which is bacterial infection of the oral cavity. If this happens, the sulphated polysaccharides in seaweed which show antimicrobial activity can help. The gelling properties of seaweed polysaccharides also appear to enhance their dental health effect. The consumption of edible treats containing brown seaweeds such as Ascophyllum nodosum efficiently decreased plaque and calculus accumulation in dogs (Gawor et al, 2018). Dogs treated with A. nodosum extract also exhibited significantly better oral health status (e.g., better oral health index and gingival bleeding index) compared to a placebo-control group.
Suppression of harmful GI bacteria
Sulphated polysaccharides extracted from different seaweeds such as Laminaria japonica, A. nodosum or Undaria pinnafitida have been demonstrated to have an inhibitory effect on the growth of pathogenic bacteria (De Jesus Raposo et al, 2015). Extracts rich in either laminarin or fucoidan fibres isolated from Laminaria spp decreased the fecal E. coli populations in pigs and reduced bacterial load in raw meat products (McDonnel et al, 2010).
Increasing nutrient availability
The soluble fibre from seaweed polysaccharides are fermented by beneficial bacteria in the hindgut, producing short chain fatty acids (SCFA) that are the primary energy source for the colonic intestinal cells. Butyrate, one of these SCFA, also serves as a key signalling compound in the hindgut by controlling the intestinal defence system (Schmitz and Suchodolski, 2016; Pilla and Suchodolski, 2020). This improved gut health in the presence of seaweed fibres can improve nutrient uptake, leading to a healthier and more active pet.
Reducing Faecal Odour
In addition to being unpleasant for dog owners, intense faecal odours are often an indication of maldigestion, dysbiosis (a disturbance of the normal microbiota profile) or the presence of pathogenic bacteria. These intense faecal odours are due to bacterial breakdown of undigested proteins, producing ammonia, amines, indols, phenols and volatile sulphur-containing compounds (Hesta et al., 2003). Diet type, particularly dietary soluble fibre, can impact faecal odour. The lack of soluble fibres, which are indigestible in the stomach and intestines, to provide substrates for the beneficial bacteria in the colon or hindgut is the principal cause of dysbiosis. Other factors include the use of antibiotics and infection by pathogenic bacteria. The high content of soluble fibre in seaweeds provide an excellent substrate for the bacteria in the hindgut that produce energy and vitamins for the animal and create a favourable gut environment.
Experience with OceanFeed Pet
Ocean Harvest Technology recently tested OceanFeedTM Pet, a propriety optimized blend of green, red, and brown seaweeds, with a total of 50 family pets varying in breed, size and age. These 50 dogs
Figure 1: The polysaccharides in brown, green and red seaweeds:
Green Red Brown
were fed OceanFeedTM Pet mixed with their standard diet for 4 weeks. At the end of the trial, 88% of the dogs were reported to have improved digestive health, including reduced diarrhoea and firmer stools. The same percentage, 44 out of 50 dogs, were also reported to have improved coat or skin condition, such as softer or shinier coats and reduced flaking. Twenty of these dogs were reported to exhibit improved energy or stamina, particularly during hot weather, while 15 were reported to have better smelling breath, likely due to the previously discussed prebiotic effect of seaweed across the GI tract.
But beware Mineral Contents!
Seaweeds can accumulate different minerals to a greater or lesser extent, depending on species and growing conditions and location. Two minerals, iodine, and arsenic are of particular concern with respect to animal health, particularly for brown seaweed. The iodine content in for example A. nodosum, commonly known as kelp, can vary from around 500-900 mg/ kg (Table 1). With an EFSA (2005) Maximum Tolerable Level of 4 mg/ kg (ppm) for iodine in dog diets, this means that kelp inclusion should be kept under 5 g/kg (0.5%) of dog food. However, green seaweeds such as Ulva (OceanFeedTM Green) and seaweed blends such as OceanFeedTM Pet have much lower iodine levels and can be safely included at up to 50 mg/kg (5%) of the dog food.
Brown seaweeds can also contain high levels of arsenic. EU directive 2002/32/EC (Official Journal L 140, as amended in L 328) on undesirable substances in animal feed has defined the maximum level of total arsenic allowed in seaweed meal and materials derived from seaweed for animal feed as 40 mg/kg. While kelps can often exceed this figure, green and appropriate blends of seaweed can fall well below this maximum level (Table 1).
Table 1. Attributes of brown, green or blended seaweeds
Seaweed Ascophyllum nodosum OceanFeedTM
Green OceanFeedTM
Pet Blend of
Brown Green
Green, Red & Brown Iodine (mg/kg) 500-900 10-40 140-150
Arsenic (mg/ kg)
35-45 4-5 7-10
Relative
palatability
Poor High Medium
Relative gut function
Medium Medium High
Green seaweed such as Ulva spp, known as ‘sea lettuce’ and used in OceanFeedTM Green, is widely used as a food condiment and is more palatable than standard kelp (Table 1). However, for gut function a blend of green, red and brown seaweeds, such as in OceanFeedTM Pet, with the resultant spectrum of beneficial fibres and other bioactives, is optimal. References: available upon request
100% Premium blend of Red, Green and Brown Seaweeds
NATURAL PRODUCT SUSTAINABLY HARVESTED
Improves gut balance Prebiotic soluble fibre A good source of Omega-3 Improves nutrient and mineral uptake
