ABSTRACT
Introduction: Weaning is a stressful experience in the piglet's life, and it often coincides with impaired gut health. Post-weaning diarrhea in piglets is frequently caused by enterotoxigenic Escherichia coli (E. coli). The first step of an E. coli infection is the adhesion to host-specific receptors present on enterocytes, leading to pro-inflammatory immune responses. The aim of this study was to examine if specific fiber fractions in the piglet diet can prevent E. coli adhesion and subsequent immune responses. Methods: The trial included 200 piglets (Danbred × Piétrain): 10 piglets/pen × 10 pens/dietary treatment × 2 dietary treatments. From weaning until 14 days (d14) post-weaning, piglets were fed a control diet or test diet with 2 kg/ton of a mixture of specific fiber fractions derived from Araceae root and citrus. Afterwards, 1 piglet per pen was euthanized, a section was taken at 75% of small intestinal length and E. coli colonization on the mucosal epithelium was quantified by scraping and conventional plating. From the same small intestinal section, histo-morphological indices were assessed, and mucosal scrapings were analyzed for gene expression of pro- and anti-inflammatory cytokines, and NF-kB. Analyses of specific intestinal bacteria and SCFA were performed on samples of intestinal content (small intestine, caecum, colon). Fecal samples were taken to measure myeloperoxidase (MPO), calprotectin and PAP/RAG3A as biomarkers for intestinal inflammation. Results and discussion: Piglets fed the fiber mixture tended to have decreased E. coli colonization to the mucosal epithelium (5.65 vs. 4.84 log10 CFU/g; P = 0.07), less E. coli in the caecum (8.91 vs. 7.72 log10 CFU/g; P = 0.03) and more Lachnospiraceae in the colon (11.3 vs. 11.6 log10 CFU/g; P = 0.03). Additionally, the fiber mixture tended to increase cecal butyric acid (10.4 vs. 19.1 mmol/kg; P = 0.07). No significant effect on histo-morphological indices and on gene expression of pro- and anti-inflammatory cytokines and NF-kB was observed. The fecal MPO concentration tended to decrease (20.2 vs. 10.4 ng/g; P = 0.07), indicating less intestinal inflammation. In conclusion, this study showed that specific fiber fractions from Araceae root and citrus in piglet weaner diets may decrease the risk of pathogen overgrowth by reducing E. coli adhesion and intestinal inflammation.
ABSTRACT
Background: African swine fever (ASF) is an important disease affecting swine and has a significant economic loss in both the developed and developing world. Aim: In this study, we evaluated the potential effects of medium-chain fatty acids (MCFAs) in individual and synergistic forms to prevent and/or reduce ASF virus (ASFV) infection using in vitro feed model. Methods: The cytotoxicity of MCFAs on porcine alveolar macrophages cells was evaluated by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The potential effects of MCFAs, including C8 (caprylic acid), C8-C6-C10 (caprylic acid-caproic acid-capric acid; 1:1:1 ratio) and C8-C10-C12 (caprylic acid-capric acid-lauric acid; 1:1:1 ratio) against a field ASFV strain isolated in the capital Hanoi of Vietnam, were further examined by real-time PCR and haemadsorption assays in in vitro feed model. Results: Our results indicated that all tested products do not induce cytotoxicity at the dose of 100 µg/ml and are suitable for further in vitro examination. These products have shown a strong antiviral effect against ASFV infectivity at doses of 0.375% and 0.5%. Interestingly, the synergistic MCFAs have shown clearly their potential activities against ASFV in which at a lower dose of 0.25%, pre-treatment with product two and three induced significant increases at the level of Cq value when compared to positive control and/or product 1 (p < 0.05). However, the viral titre was not changed after 24 hours post-inoculation when compared to positive control. Our findings suggested that all tested products, both individual and synergistic forms of MCFAs, have possessed a strong anti-ASFV effect, and this effect is dose-dependence in in vitro feed model. Additionally, synergistic effects of MCFAs are more effective against ASFV when compared to individual forms. Conclusion: Together, the findings in this study indicate that MCFAs, both individual and synergistic forms, inhibit against a field ASFV strain in the feed model, which may support minimizing the risk of ASF transmission in the pig population. Further studies focusing on in vivo anti-ASFV effects of MCFAs are important to bring new insight into the mode of ASFV-reduced action by these compounds in swine feed.
