The polysaccharides contained in brown, red, and green seaweeds present different bioactive molecules such as fucoidan, laminarin, alginate, ulvan, and carrageenan.
To ensure environmental sustainability, according to the European Green Deal and to boost the One Health concept, it is essential to improve animals’ health and adopt sustainable and natural feed ingredients. Over the past decade, prebiotics have been used as an alternative approach in order to reduce the use of antimicrobials, by positively affecting the gut microbiota and decreasing the onset of several enteric diseases in pig. However, dietary supplementation with seaweed polysaccharides as prebiotics has gained attention in recent years. Seaweeds or marine macroalgae contain several polysaccharides: laminarin, fucoidan, and alginates are found in brown seaweeds, carrageenan in red seaweeds, and ulvan in green seaweeds. The present review focuses on studies evaluating dietary seaweed polysaccharide supplementation in pig used as prebiotics to positively modulate gut health and microbiota composition.
Gut health, which is described as a generalized condition of homeostasis in the gastrointestinal tract
[1]
, has been recognized as playing a key role in maintaining pig health. In fact, the gut plays an important role in efficient feed digestion and absorption, for the protection of the gut barrier, the microbiota composition, and the improvement in the immune status
[2]
. In fact, commensal bacteria such as Lactobacilli and Bifidobacteria are necessary to sustain the host immune system, protecting against the colonization of opportunistic pathogens
[3]
.
Since the ban on in-feed antibiotics, reliable dietary interventions are needed that are capable of sustaining pig performance and improving gut health, by minimizing the use of antimicrobials. A large amount of evidence has reported the beneficial effects of some feed ingredients or additives in modulating gut health and microbiota in pig.
The review by Xiong et al.
[2]
focused on the effects of several feed ingredients or additives such as functional amino acids, natural extracts, and short-chain fatty acids and prebiotics on gut health in weaned pigs.
Over the past few decades, prebiotics have been used as an alternative approach aimed at reducing the use of antimicrobials, by positively affecting the gut microbiota and decreasing the onset of several enteric diseases in pig
[4]
. However, dietary supplementation with seaweed polysaccharides as prebiotics, has also gained attention in recent years. In fact, natural bioactive compounds have been considered as attractive dietary interventions in pig in order to ensure environmental sustainability, in line with the European Green Deal plan and to improve animal health according to the One Health approach.
Marine macroalgae, or seaweeds, are classified as brown algae (Phaeophyceae), red algae (Rhodophyta), and green algae (Chlorophyta) and include thousands of species. The chemical composition and the bioactive metabolite content of several species have been extensively studied, along with the variations related to species and genera, harvesting season, environmental conditions, and geographical location
. Seaweeds also contain large amounts of carboxylated and sulfated polysaccharides, with important functions for the macroalgal cells including structural and energy storage
[7]
. Seaweed polysaccharides are safe, environmental-friendly, and economical natural polymers. Seaweed polysaccharides, such as fucoidan, laminarin, ulvan, carrageenan, and alginates, show several biological activities in vitro and in vivo studies
. In fact, polysaccharides and oligosaccharides originating from seaweeds have been shown to regulate intestinal metabolism and fermentation and reduce the adhesion of pathogenic bacteria
[10]
. Several seaweed polysaccharides have also shown anti-inflammatory, antiviral, and antioxidant activities
[11]
. Considering the above mentioned properties, the present paper reviews the prebiotic effects of seaweed polysaccharides in pig nutrition.
Chemical Constituent | Brown Seaweed | Green Seaweed | Red Seaweed |
---|---|---|---|
Polysaccharides | alginate, laminarin, fucoidan (sulphated), cellulose, mannitol |
ulvan (sulphated), mannan, galactans (sulphated), xylans, starch, cellulose, lignin | carrageenans (sulphated), agar (sulphated), glucans (floridean starch), cellulose, lignin, funoran |
Monosaccharides | glucose, galactose, fucose, xylose, uronic acid, mannuronic acid, guluronic acid, glucuronic acid | glucose, mannose, rhamnose, xylose, uronic acid, glucuronic acid | glucose, galactose, agarose |
References | [12][13] | [12][13] | [12][13] |
Seaweed | Polysaccharides, % | Alginates | Carragenan | Fucoidan | Laminarin | Ulvan | References |
---|---|---|---|---|---|---|---|
Brown | |||||||
Ascophillum nodosus | 62 (42–70) |
285 (240–330) |
- | 75 (11–120) |
118 (12–120) |
- | [8][18][22][23][24][25] |
Laminaria hyperborea | 39.9 (14.4–65.5) |
215 (22–408) |
- | 30 (20–40) |
125 (0–320) |
- | [8][18][26][27][28] |
Laminaria digitata | 57.3 (44–70.7) |
435 (350–520) |
- | 49.5 (22–112) |
120 (0–350) |
- | [8][18][26][27][29][30][31] |
Laminaria sp. * | 45 (13–77) |
309 (225–343) |
- | 147.5 (22–550) |
153 (62.4–340) |
- | [8][26][29][32][33][34][35] |
Fucus sp. # | 57 (34.5–66) |
162 | - | 105 (11–200) |
2.3 (0.4–3.8) |
- | [18][23][24][27][34][36][37][38] |
Sargassum sp. ⁑ | 36 (4–68) | 296 (93–499) |
- | 38 (31–45) |
3 (0–6) |
- | [18][34][36] |
Saccharina sp. ** | 69 (58–80) |
242.5 (200–285) |
- | 33 (13–80) |
97.5 (0–330) |
- | [5][8][18][23][27][29][39] |
Undaria pinnafitica | 40 (35–45) |
425 (340–510) |
- | 219 (30–690) |
30 | - | [8][18][29][40] |
Red | - | - | - | - | - | ||
Chondrus crispus | 60.5 (55–66) |
- | 439.5 (338–510) |
- | - | - | [18][34][41] |
Kappaphycus alvarezii | 58 (53.5–64) |
- | 448.5 (187–756) |
- | - | - | [32][41][42][43] |
Green | - | ||||||
Ulva sp. § | 42 (15–65) |
- | - | - | - | 176 (11–400) |
[18][34][44][45][46][47][48] |
The effects of algae polysaccharides as prebiotics in sows have been evaluated by several authors.
The effects of polysaccharides in the gut are usually assessed by evaluating the SCFA content and the intestinal microbiota composition and/or the presence of beneficial bacteria
[55]
. The effects of dietary supplementation with seaweeds in sows can modulate the productive performances and health of lactating piglets, making them more resistant to pathogens.