Lauric acid and microencapsulated zinc oxide have divergent effects on weaned pig growth performance, jejunal barrier...

Pharmacological zinc oxide (ZnO) and medium-chain fatty acids (MCFAs) have been evaluated as dietary interventions during the weaning phase. However, the effects of microencapsulated ZnO and C12:0, lauric acid (LA), are highly debated and poorly understood. Therefore, the objective of this study was to evaluate the independent and combined effects of LA and microencapsulated ZnO on growth performance, intestinal barrier function, and intestinal transcriptomic profiles in weaned pigs. A total of 256 pigs (21 days of age) were blocked by sex and assigned to 1 of 4 dietary treatments for 28 days: 1) basal diet-formulated to supply 110 mg/kg zinc (CON), 2) basal diet + 2% LA (LAU), 3) basal diet + 300 mg/kg microencapsulated ZnO (mZnO), or 4) basal diet + 2% LA and 300 mg/kg microencapsulated ZnO (MIX). Body weight and feed intake were recorded weekly. At day 28, six pigs per treatment were euthanized for tissue collection. Jejunal explants were collected to assess barrier function and integrity using modified Ussing chambers. Additional jejunum and ileum samples were collected for RNA sequencing and transcriptomic analysis. A main effect of mZnO was observed for body weight on days 14 (P = 0.0346), 21 (P = 0.006), and 28 (P = 0.0001) as pigs fed mZnO had heavier body weights. There were no significant effects of LAU, mZnO, or their interaction detected for feed intake. A significant LAU × mZnO interaction was observed for average daily gain over the 28-d study period (P = 0.019). LAU tended to reduce transepithelial resistance (TER) (P = 0.071), whereas mZnO tended to increase TER (P = 0.068). Transcriptomic analysis revealed 76 differentially expressed genes enriched for immune-related pathways in the jejunum of MIX versus CON treatments (P < 0.05). Collectively, these findings indicate that dietary mZnO improved growth and tended to enhance barrier integrity. Adding LA did not further increase performance but altered the jejunal transcriptome.