doi:10.1002/jsfa.70359engMuñoz-Grein, JenniferLópez, RutSolanas, EstelaFondevila, ManuelBelanche, AlejandroIn 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 cellsART-2026-147338BACKGROUND: Weaning represents a significant digestive challenge for dairy ruminants due to their underdeveloped rumenmicrobiota resulting from early separation from their dams shortly after birth. This study aimed to optimize the weaning pro-cess by evaluating six commercial feed additives, including four blends of essential oils (BEOs), a probiotic (live yeast) and a pre-biotic (pectin). The effects on rumen fermentation were evaluated using batch cultures with rumen inocula collected at thepost-weaning period from artificially reared lambs, whereas the effects on gut health indicators were assessed using Caco-2 cellmonolayers.RESULTS: Most tested additives showed minor benefits on rumen fermentation, even at higher doses (600 mg L−1 ). A BEO con-taining turmeric, thymol and yeast cell wall promoted a shift towards propionic fermentation, whereas supplementation withpectin decreased NH3 -N concentrations. Conversely, all four BEOs positively influenced intestinal health, resulting in improvedCaco-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 theirimmature rumen microbiota, absence of protozoa, and low rumen pH. Nevertheless, this in vitro study suggests that certainBEOs may enhance intestinal health by improving cell viability and reducing inflammation. Further in vivo studies are neededto confirm these findings.2026http://zaguan.unizar.es/record/16794710.1002/jsfa.70359http://zaguan.unizar.es/record/167947oai:zaguan.unizar.es:167947info:eu-repo/grantAgreement/ES/AEI/MICNN/PID2021-123206OB-I00info:eu-repo/grantAgreement/ES/MICINN/RYC2019-027764-I/AEI/10.13039/501100011033Journal of the science of food and agriculture 106, 4 (2026), 2168-2179All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/embargoedAccess