AimIn vitro and invivo studies were conducted to test a new carvacrol-based product designed to delay the carvacrol release so that it could reach the caeca of broiler chickens in order to control Campylobacter jejuni. Methods and ResultsAntimicrobial activity of carvacrol, a constituent of oregano and thyme essential oil, has been demonstrated against C. jejuni invitro, and this compound was found beneficial for broiler growth. Here, we tested a new liquid formulation that did not change the antibacterial efficacy of carvacrol against C. jejuni invitro, as assessed by broth microdilution. The mode of action of carvacrol also remained unchanged as illustrated by electronic microscopy. A pharmacokinetic assay monitored carvacrol of the solid galenic formulation in the avian digestive tract and this showed that this compound was mainly found in the last part (caeca, large intestine) and in the droppings. Extremely low concentrations of free carvacrol were present in blood plasma, with larger amounts of carvacrol metabolites: carvacrol glucuronide and sulphate. A qPCR analysis showed that the solid galenic form of carvacrol added at 5kg per tonne of food (i.e. 95mg of carvacrol per kg of bodyweight per day) significantly decreased the C. jejuni caecal load by 15 log. ConclusionsThe new liquid formulation was as effective as unformulated carvacrol invitro. In vivo the solid galenic form seems to delay the carvacrol release into the caeca and presented interesting results on C. jejuni load after 35days. Significance and Impact of the StudyResults suggested that this product could be promising to control Campylobacter contamination of broilers.