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- PublicationIn vitro and in vivo investigation of the potential of dietary natural bioactives to improve parameters of the gastrointestinal health in weaned pigs and broiler chickens(University College Dublin. School of Veterinary Medicine, 2021)The main research objective of this thesis was to evaluate the potential of candidate dietary supplements, namely casein hydrolysate (CH) and its 5 kDa retentate (5kDaR), yeast ß-glucan and crude fucoidan- and laminarin-rich seaweed extracts, to promote growth and gastrointestinal health in weaned pigs with a focus on modulating the composition of the gastrointestinal microbiota. The first three experimental chapters (Chapter 2-4) involved an initial assessment of the different dietary candidates for their antibacterial and prebiotic effects using two in vitro GIT microbiota models: 1) a batch fermentation assay inoculated with faeces from weaned pigs, and; 2) a panel of pure culture growth assays with selected beneficial (Lactobacillus plantarum, L. reuteri, Bifidobacterium thermophilum) and pathogenic (Salmonella Typhimurium, enterotoxigenic Escherichia coli) bacterial strains. Chapter 2 focused on CH, 5kDaR and yeast ß-glucan and whether CH could substitute 5kDaR, whereas Chapters 3 and 4 investigated how seaweed species, harvest season and extraction methodologies/conditions influenced the antibacterial and prebiotic potential of the whole biomass samples and extracts of Ascophyllum nodosum and Laminaria spp., respectively. During the in vitro assessment of the dietary candidates, an A. nodosum extract (ANE1) produced using the E1 extraction conditions of a novel hydrothermal-assisted extraction (HAE) methodology exhibited a strong antibacterial activity against S. Typhimurium and ETEC and, thus, was selected for further in vivo investigation. In Chapter 5, a new fucoidan-rich A. nodosum extract (ANE) produced using the above-mentioned extraction protocol, was evaluated at two inclusion levels (high and low) as a dietary intervention to control Salmonella infection in naturally infected weaned pigs and improve parameters of gastrointestinal health. ANE exhibited similar in vitro antibacterial activity to the ANE1. High ANE supplementation reduced Salmonella shedding during the post-weaning period; however, no benefits were observed in Salmonella shedding and intestinal colonisation following movement to the grower houses, regrouping and experimental re-infection with S. Typhimurium. High ANE supplementation led to a more beneficial colonic microbiota, characterised by reduced Enterobacteriaceae counts and increased Bifidobacterium spp. counts, and reduced expression of inflammatory markers that facilitate Salmonella colonisation and persistence. Fucoidan was considered the bioactive component, as it was the major constituent of ANE. The second research objective of this thesis was to evaluate the potential of a laminarin-rich extract as a dietary supplement in broiler chickens based on its previous beneficial effects on growth and gastrointestinal health in pigs, as these two animal species share similarities in terms of gastrointestinal ecosystem and production and intestinal challenges. In Chapter 6, dietary supplementation with 300 ppm laminarin improved performance, increased the caecal Bifidobacterium spp. population and enhanced nutrient absorption, intestinal integrity and protective immune responses indicating improved resistance to intestinal pathogens without compromising growth. Overall, seaweed extracts are promising dietary supplements to enhance performance and gastrointestinal health in broiler chickens and, potentially under challenging conditions in pigs, thus, meriting further exploration. Nevertheless, prior in vitro evaluation and purification of the bioactive components are required to improve their efficacy in in vivo conditions.
- PublicationIn vitro effects of seaweed extracts on intestinal commensals and pathogens of weaned piglets(Microbiology Society, 2018-06-21)
; ; ; ; ;While the inclusion of certain seaweed extracts in weaner piglet diets leads to a beneficial gut microbial profile, the mode of action is not known. The aim of this study was to evaluate the prebiotic and antimicrobial potential of Laminaria digitata and Ascophylum nodosum extracts in vitro. Both extracts were two-fold diluted from 2 mg/ml to 0.25 mg/ml. The following strains were used at 106 -107 colonyforming unit(CFU)/ml concentrations: Lactobacillus plantarum, L. reuteri, Bifidobacterium thermophilum, Enterotoxigenic Escherichia coli O149 and Salmonella enterica ser Typhimurium PT12. Each concentration of each extract and controls (0 mg/ml) were incubated for 18 h at 37 °C aerobically or anaerobically (B. thermophilum). Final bacterial concentrations were determined by spread plating. All experiments were carried out with technical replicates on three independent occasions. All data were logarithmically transformed and analysed using the PROC GLM (SAS 9.4). The L. digitata extract increased B. thermophilum 0.7 LogCFU/ml at 0.25 mg/ml (P<0.05) and ≥1 LogCFU/ml from 0.5-2 mg/ml (P<0.05), with no effect on lactobacilli. The A. nodosum extract increased B. thermophilum up to 0.9 LogCFU/ml at all concentrations tested (P<0.05). Additionally, a 0.2 LogCFU/ml increase of L. reuteri and L. plantarum was observed at 2 mg/ml (P<0.05) and 1mg/ml (P<0.05), respectively. Both extracts displayed no antimicrobial activity against ETEC or S. Typhimurium. In conclusion, both extracts exhibited bifidogenic activity in vitro, with an additional slight increase of Lactobacillus spp. for A. nodosum, indicating a prebiotic potential. 38
- PublicationEffects of extraction method on the prebiotic potential of Ascophylum nodosum extracts(Microbiological Society, 2018-06-28)
; ; ; ; ;Seaweed-derived bioactive compounds exhibit various beneficial activities in humans and animals. A factor influencing their concentrations, and subsequent bioactivity, is the extraction method. Our aim was to evaluate the in vitro prebiotic potential of three differently-extracted Ascophylum nodosum samples. The samples were produced using either solid-liquid extraction with water (AN-W), or ethanol (AN-EtOH) as solvent or high pressure-assisted extraction with water as solvent (AN-HPW). All extracts were two-fold diluted from 2 mg/ml to 0.25 mg/ml. Lactobacillus plantarum (LP), L. reuteri (LR) and Bifidobacterium thermophilum (BT) were used at 106 -107 colony-forming unit(CFU)/ml. Each concentration of each extract and controls (0 mg/ml) were incubated for 18 h at 37 °C aerobically or anaerobically (BT). Final bacterial concentrations were determined by spread plating. All experiments were carried out in triplicate with technical replicates. All data were logarithmically transformed and analysed using PROC GLM (SAS 9.4). AN-HPW increased BT (≤0.9 LogCFU/ml, P<0.05) at all concentrations and LR and LP (0.2 LogCFU/ml, P<0.05) at 2 mg/ml and 1mg/ml, respectively. AN-W increased BT (≤0.6 LogCFU/ml, P<0.05) at 1-2mg/ml, but decreased both lactobacilli; LP ≤0.7 LogCFU/ml and LR ≤5.4 LogCFU/ml at all concentrations (P<0.05). AN-EtOH increased LP (≤0.7 LogCFU/ml, P<0.05), but reduced LR (≤5.7 LogCFU/ml, P<0.05) at all concentrations and BT (≤4 LogCFU/ml, P<0.05) at 1-2 mg/ml. In conclusion, the extraction method influenced the prebiotic potential of the A. nodosum extracts in vitro with AN-HPW being the most promising. 23
- PublicationPotential of a fucoidan-rich Ascophyllum nodosum extract to reduce Salmonella shedding and improve gastrointestinal health in weaned pigs naturally infected with Salmonella(Springer, 2022-04-04)
; ; ; ; ; ; ; ; ;Background. Dietary supplementation with a fucoidan-rich Ascophyllum nodosum extract (ANE), possessing an in vitro anti-Salmonella Typhimurium activity could be a promising on-farm strategy to control Salmonella infection in pigs. The objectives of this study were to: 1) evaluate the anti-S. Typhimurium activity of ANE (containing 46.6% fucoidan, 18.6% laminarin, 10.7% mannitol, 4.6% alginate) in vitro, and; 2) compare the effects of dietary supplementation with ANE and Zinc oxide (ZnO) on growth performance, Salmonella shedding and selected gut parameters in naturally infected pigs. This was established post-weaning (newly weaned pig experiment) and following regrouping of post-weaned pigs and experimental re-infection with S. Typhimurium (challenge experiment). Results. In the in vitro assay, increasing ANE concentrations led to a linear reduction in S. Typhimurium counts (P < 0.05). In the newly weaned pig experiment (12 replicates/treatment), high ANE supplementation increased gain to feed ratio, similar to ZnO supplementation, and reduced faecal Salmonella counts on d 21 compared to the low ANE and control groups (P < 0.05). The challenge experiment included thirty-six pigs from the previous experiment that remained on their original dietary treatments (control and high ANE groups with the latter being renamed to ANE group) apart from the ZnO group which transitioned onto a control diet on d 21 (ZnO-residual group). These dietary treatments had no effect on performance, faecal scores, Salmonella shedding or colonic and caecal Salmonella counts (P > 0.05). ANE supplementation decreased the Enterobacteriaceae counts compared to the control. Enterobacteriaceae counts were also reduced in the ZnO-residual group compared to the control (P < 0.05). ANE supplementation decreased the expression of interleukin 22 and transforming growth factor beta 1 in the ileum compared to the control (P < 0.05). 71