ISSUE FOCUS FEED & ADDITIVE MAGAZINE May 2022 27 intestine, modulate the immune response and to provide signals that effect behaviour of the host animal (Maslowski and Mackey, 2011; Stanley et al, 2014; LaBlanc et al 2017; Mesa et al, 2017). In healthy animals consuming a nutrient adequate diet, the microbial community has a specific composition (Borda-Molina et al, 2018; Tröscher-Mußotter et al, 2019). Poor diet, stress, infection, or other environmental challenges can alter the normal profile of the GI microbiota resulting 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 genomic techniques have shed new light on the prebiotic effect of seaweed polysaccharides on the GI microbiota profile and related physiological effects (Borda Molina et al, 2018; Tröscher-Mußotter et al, 2019). Using metagenomic analyses, chicken cecal 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 are the more abundant species in the chicken ceca (Borda Molina et al, 2018). The dominant phyla in the pig’s cecaum are the Firmicutes and Bacteroidetes, which account for mor ethan 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 Rumminococcaceae (3.7%) as reported by Tröscher-Mußotter et al, (2019). In cattle, the core microbiome of the rumen displays a distinct profile (Lamendella et al, 2011). This core microbiome in the rumen changes when diet-type changes between forage and high grain diets. Bacteroidetes and Firmicutes are the core phyla in the rumen of cattle consuming all diet types. When cattle are fed a high grain diet, Proteobacteria become the dominant phyla. With forage based diets, the Ruminococcaceae and Lachnospiraceae families are most prevalent. These changes in the core microbiota of the rumen, suggest it may be possible to effect changes in the rumen microbiota with seaweed polysaccharides. SEAWEED POLYSACCHARIDES Unique polysaccharides or fibre found only in seaweed, account for around 30-75% of the dry weight of seaweeds, where they serve a structural role in cell walls (Xu et al, 2017). Of the total fibre in seaweed, only a proportion are soluble polysaccharides, posessing prebiotic activity. The soluble polysaccharides comprise around 55–65 % of total fibre in commonly used green and red seaweed but may be above 80 % in commonly used brown seaweed (Lahaye 1991; Figure 1). These soluble polysaccharides are particularly effective prebiotics in animals (Hentati et al, 2020). Figure 1: The fibre profile of brown, green and red seaweeds expressed as the median reported value in g/kg of dry weight (Overland et al, 2018).
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