Effects of monoglyceride blend on systemic and intestinal immune responses, and gut health of weaned pigs experimentally infected with a pathogenic Escherichia coli

Abstract

Background: Monoglycerides have emerged as a promising alternative to conventional practices due to their biological activities, including antimicrobial properties. However, few studies have assessed the efficacy of monoglyceride blend on weaned pigs and their impacts on performance, immune response, and gut health using a disease challenge model. Therefore, this study aimed to investigate the effects of dietary monoglycerides of short- and medium-chain fatty acids on the immunity and gut health of weaned pigs experimentally infected with an enterotoxigenic Escherichia coli F18.

Results: Pigs supplemented with high-dose zinc oxide (ZNO) had greater (P < 0.05) growth performance than other treatments, but no difference was observed in average daily feed intake between ZNO and monoglycerides groups during the post-challenge period. Pigs in ZNO and antibiotic groups had lower (P < 0.05) severity of diarrhea than control, but the severity of diarrhea was not different between antibiotic and monoglycerides groups. Pigs fed with monoglycerides or ZNO had lower (P < 0.05) serum haptoglobin on d 2 or 5 post-inoculation than control. Pigs in ZNO had greater (P < 0.05) goblet cell numbers per villus, villus area and height, and villus height:crypt depth ratio (VH:CD) in duodenum on d 5 post-inoculation than pigs in other treatments. Pigs supplemented with monoglycerides, ZNO, or antibiotics had reduced (P < 0.05) ileal crypt depth compared with control on d 5 post-inoculation, contributing to the increase (P = 0.06) in VH:CD. Consistently, pigs in ZNO expressed the lowest (P < 0.05) TNFa, IL6, IL10, IL12, IL1A, IL1B, and PTGS2 in ileal mucosa on d 5 post-inoculation, and no difference was observed in the expression of those genes between ZNO and monoglycerides. Supplementation of ZNO and antibiotic had significant impacts on metabolic pathways in the serum compared with control, particularly on carbohydrate and amino acid metabolism, while limited impacts on serum metabolites were observed in monoglycerides group when compared with control.

Conclusions: The results suggest that supplementation of monoglyceride blend may enhance disease resistance of weaned pigs by alleviating the severity of diarrhea and mitigating intestinal and systemic inflammation, although the effectiveness may not be comparable to high-dose zinc oxide.

Keywords: Diarrhea; Enterotoxigenic Escherichia coli; Gut health; Monoglycerides; Systemic immunity; Weaned pigs.

Fig. 1

Daily fecal score of enterotoxigenic Escherichia coli F18-challenged weaned pigs fed diets supplemented with monoglycerides, high-dose zinc oxide (ZNO), or antibiotic. Fecal score = 1, normal feces; 2, moist feces; 3, mild diarrhea; 4, severe diarrhea; 5, watery diarrhea. ^*P < 0.05, indicating fecal scores were significantly different among treatments. ^#P < 0.10, indicating fecal scores tended to different among treatments. Each least squares mean represents 14–15 observations before d 5 post-inoculation (PI) and each least squares mean represents 8–9 observations after d 5 PI

Fig. 2

Frequency of diarrhea (overall period) of enterotoxigenic Escherichia coli F18-challenged weaned pigs fed diets supplemented with monoglycerides, high-dose zinc oxide (ZNO), or antibiotic. Frequency of diarrhea was calculated as the percentage of pig days with fecal score ≥ 3 or 4 in the total of pig days. ^a–cMeans without a common superscript are different (P < 0.05) in frequency of diarrhea ≥ 3. ^A–CMeans without a common superscript are different (P < 0.05) in frequency of diarrhea ≥ 4

Fig. 3

The percentage (%) of β-hemolytic coliforms in fecal samples of enterotoxigenic Escherichia coli F18-challenged pigs fed diets supplemented with monoglycerides, high-dose zinc oxide (ZNO), or antibiotic. No β-hemolytic coliforms were observed in the fecal samples of pigs before Escherichia coli challenge. β-Hemolytic coliforms were only observed in control pigs on d 21 post-inoculation (PI). Each least squares mean represents 14–15 observations on d 2 and 5 PI and each least squares mean represents 8–9 observations on d 7, 10, 14, and 21 PI. ^a,bMeans without a common superscript are different (P < 0.05)

Fig. 4

Relative mRNA abundance of genes in jejunal mucosa of enterotoxigenic Escherichia coli F18-challenged weaned pigs fed diets supplemented with monoglycerides, high-dose zinc oxide, or antibiotic. Each least squares mean represents 6–9 observations. PI, Post-inoculation; MUC2, Mucin 2; CLDN1, Claudin-1; ZO-1, Zonula occludens-1; OCLN, Occludin

Fig. 5

Relative mRNA abundance of genes in ileal mucosa of enterotoxigenic Escherichia coli F18-challenged pigs supplemented with monoglycerides, high-dose zinc oxide, or antibiotic on d 5 (A) and 21 PI (B). ^a,bMeans without a common superscript are different (P < 0.05). Each least squares mean represents 6–9 observations. PI, Post-inoculation; TNFa, Tumor necrosis factor-alpha; IL6, Interleukin 6; IL7, Interleukin 7; IL10, Interleukin 10; IL12, Interleukin 12; IL1A, Interleukin-1 alpha, IL1B, Interleukin-1 beta; MUC2, Mucin 2, and PTGS2, Prostaglandin-endoperoxide synthase 2

Fig. 6

Partial Least Squares Discriminant Analysis (PLS-DA) 2D score plot of the metabolites in serum showed separated clusters between the CON and ZNO, MG and ZNO, MG and AB, and ZNO and AB groups on d 5 (A) and/or d 14 (B) post-inoculation, respectively. CON = Control; MG = Monoglycerides; ZNO = High-dose zinc oxide; AB = Antibiotic. Shaded areas in different colors represent in 95% confidence interval