Effects of Dietary Valerate Glycerides on Serum Inflammatory Markers, Serum Metabolomic Profile, and Intestinal Mucosa Gene Expression in Weanling Pigs Infected with a Pathogenic Escherichia Coli

Lauren L Kovanda, Sofia Rengman, Snehal Tawde, Jeroen Pos, Kwangwook Kim, Yanhong Liu

Our previous work showed that dietary valerate glycerides reduced frequency of diarrhea and β-hemolytic coliforms in fecal cultures of pigs infected with F18+ Enterotoxigenic Escherichia coli (ETEC). However, the impact of these feed additives on the immune response and intestinal physiology of newly weaned pigs experiencing ETEC-associated diarrhea has not been evaluated. The present experiment aimed to determine the effects of dietary valerate glycerides on intestinal mucosa gene expression, systemic inflammatory status, and serum metabolomic profile of weanling piglets infected with F18+ ETEC. Sixty weaned piglets (6.97 ± 0.75 kg body weight; 21 days old) were randomly assigned to one of four dietary treatments: nursery basal diet (control), 0.075% or 0.1% monovalerin, or 0.1% trivalerin added to control. After a 7-day adaptation, all piglets were orally inoculated with F18+ ETEC (1010 CFU/3 mL) on d 0, d 1, and d 2 post-inoculation (PI). Serum samples were collected on d 0 prior to ETEC inoculation, d 3, d 6, and d 21 PI to analyze concentration of tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and haptoglobin. Serum samples from d 6 PI were submitted for untargeted metabolomics analysis at the West Coast Metabolomics Center. Six replicate pigs per treatment group were euthanized on d 7 PI to collect jejunal and ileal mucosa for gene expression analysis. Data were analyzed in RStudio by ANOVA in a linear mixed model with treatment as fixed effect and pig as random effect. Metabolomics analysis was performed using the online platform, MetaboAnalyst. Pigs fed trivalerin had reduced (P < 0.05) serum TNF-α on d 0 and d 6 PI compared with pigs in control. Whereas pigs supplemented with 0.1% monovalerin tended (P ≤ 0.10) to have decreased serum TNF-α on d 0 and d 3 PI, and less (P < 0.05) serum CRP on d 3 PI compared with pigs in control. No differences in serum concentrations of haptoglobin were detected among dietary treatments. Preliminary results for gene expression analysis indicate a tendency (P = 0.078) for increased mRNA expression of tight junction protein, ZO-1 in pigs fed 0.1% trivalerin compared with control. Among all valerate derivative treatments, significant fold changes [FC > 2, log2(FC) > 1] for individual metabolites were detected, where levels of adenosine, putrescine, and shikimic acid were decreased compared with the control group. No differential metabolomic profiles in serum were identified on d 6 PI as indicated by a lack of cluster separation using principal component analysis (PCA). In conclusion, valerate glycerides could regulate gene expression of the intestinal epithelium and systemic immune response of weanling piglets infected with F18+ ETEC.