In vitro screening of essential oil blends, probiotics and prebiotics to optimize post‐weaning in artificially reared ruminants: effects on rumen fermentation and gut health indicators in Caco‐2 cells

Abstract BACKGROUND Weaning represents a significant digestive challenge for dairy ruminants due to their underdeveloped rumen microbiota resulting from early separation from their dams shortly after birth. This study aimed to optimize the weaning process by evaluating six commercial feed additives, including four blends of essential oils ( BEOs ), a probiotic (live yeast) and a prebiotic (pectin). The effects on rumen fermentation were evaluated using batch cultures with rumen inocula collected at the post‐weaning period from artificially reared lambs, whereas the effects on gut health indicators were assessed using Caco‐2 cell monolayers. RESULTS Most tested additives showed minor benefits on rumen fermentation, even at higher doses (600 mg L −1 ). A BEO containing turmeric, thymol and yeast cell wall promoted a shift towards propionic fermentation, whereas supplementation with pectin decreased NH 3 ‐N concentrations. Conversely, all four BEOs positively influenced intestinal health, resulting in improved Caco‐2 cell viability and lower levels of pro‐inflammatory interleukin ‐6. CONCLUSION Modulating rumen fermentation during the post‐weaning in artificially reared lambs is challenging due to their immature rumen microbiota, absence of protozoa, and low rumen pH . Nevertheless, this in vitro study suggests that certain BEOs may enhance intestinal health by improving cell viability and reducing inflammation. Further in vivo studies are needed to confirm these findings. © 2025 Society of Chemical Industry.