ABSTRACT This study aimed to evaluate the potential of two new fat-protected butyrate or heptanoate salts to improve gut health and control post-weaning colibacillosis in weaning piglets challenged with enterotoxigenic Escherichia coli (ETEC) F4+, particularly focusing on their impact on intestinal microbiota and fermentative activity along the gastrointestinal tract (GIT). Seventy-two 21-d-old pigs were fed a plain diet (CTR) or supplemented with sodium butyrate (BUT) or sodium heptanoate (HPT), both at 0.3%. After a week of adaptation, animals were orally challenged at days 8 and 9 with 5.8 · 109 and 6.6 · 1010 cfu, respectively, and were euthanised on d 4 and d 8 post-inoculation (PI) (n = 8) to collect blood, digesta and tissue samples and characterise microbial groups, pathogen loads (qPCR), fermentation, ileal histomorphometry and immune markers. Colonic microbiota was analysed by 16S rRNA gene MiSeq sequencing. Supplementing both acid salts did not compensate clinical challenge effects nor performance impairments and neither histomorphometry nor serum biomarkers. Changes in the gastric fermentative activity were registered, BUT reducing lactic acid concentrations (day 8 PI), and with HPT fewer animals presenting detectable concentrations of propionic, butyric and valeric acids. At ileum BUT increased acetic acid concentration (day 8 PI), and both additives reduced short-chain fatty acids (SCFA) in the colon. Increases in enterobacteria and coliforms counts in ileal digesta (day 4 PI, p < 0.10) and mucosa scrapes (p < 0.05) were registered although E. coli F4 gene copies were unaffected. Regarding changes in the colonic microbiota (day 4 PI), Prevotellaceae and Prevotella were promoted with BUT supplementation whereas only minor groups were modified in HPT-treated animals. Summarising, although the pathogen loads or inflammatory mediators remained unresponsive, butyrate and heptanoate showed a significant impact on microbial fermentation along the whole GIT, being able to modify different bacterial groups at the colon. It could be hypothesised that these effects might be mediated by a carry-over effect of the changes observed in gastric fermentation, but possibly also to a better nutrient digestion in the foregut as a result of the reduced colonic SCFA concentrations.

中文翻译：

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在接受 ETEC F4+ 攻击的断奶仔猪中，胃肠道发酵活性和结肠微生物群对受保护的丁酸钠和受保护的庚酸钠的反应

摘要 本研究旨在评估两种新的脂肪保护的丁酸盐或庚酸盐在改善肠道健康和控制断奶后大肠杆菌 (ETEC) F4+ 感染的断奶仔猪中的潜力，特别关注它们对肠道微生物群和肠道菌群的影响。沿胃肠道 (GIT) 的发酵活性。72 头 21 日龄猪被喂以普通饮食 (CTR) 或补充丁酸钠 (BUT) 或庚酸钠 (HPT)，两者均为 0.3%。适应一周后，在第 8 天和第 9 天分别用 5.8·109 和 6.6·1010 cfu 对动物进行口服攻击，并在接种后 (PI) 的第 4 天和第 8 天实施安乐死 (n = 8) 以收集血液、食糜和组织样本，并表征微生物群、病原体载量 (qPCR)、发酵、回肠组织形态计量学和免疫标志物。通过 16S rRNA 基因 MiSeq 测序分析结肠微生物群。补充两种酸式盐并不能补偿临床挑战效应或性能损害，也不能补偿组织形态学或血清生物标志物。记录了胃发酵活性的变化，但降低了乳酸浓度（感染后第 8 天），并且 HPT 减少了呈现可检测浓度的丙酸、丁酸和戊酸的动物。在回肠 BUT 增加乙酸浓度（感染后第 8 天），两种添加剂都减少了结肠中的短链脂肪酸 (SCFA)。尽管大肠杆菌 F4 基因拷贝未受影响，但记录了回肠食糜（感染后第 4 天，p < 0.10）和粘膜擦伤（p < 0.05）中肠杆菌和大肠菌数量的增加。关于结肠微生物群的变化（感染后第 4 天），BUT 补充促进了普氏菌科和普氏菌，而在 HPT 治疗的动物中只有少数群体发生了改变。总而言之，虽然病原体负荷或炎症介质仍然没有反应，但丁酸盐和庚酸盐对整个胃肠道的微生物发酵有显着影响，能够改变结肠中的不同细菌群。可以假设，这些影响可能是由胃发酵中观察到的变化的遗留效应介导的，但也可能是由于结肠 SCFA 浓度降低导致前肠中更好的营养消化。尽管病原体负荷或炎症介质仍然没有反应，但丁酸盐和庚酸盐对整个胃肠道的微生物发酵有显着影响，能够改变结肠中的不同细菌群。可以假设，这些影响可能是由胃发酵中观察到的变化的遗留效应介导的，但也可能是由于结肠 SCFA 浓度降低导致前肠中更好的营养消化。尽管病原体负荷或炎症介质仍然没有反应，但丁酸盐和庚酸盐对整个胃肠道的微生物发酵有显着影响，能够改变结肠中的不同细菌群。可以假设，这些影响可能是由胃发酵中观察到的变化的遗留效应介导的，但也可能是由于结肠 SCFA 浓度降低导致前肠中更好的营养消化。