Encapsulation of essential oils of rosemary (Rosmarinus officinalis): evaluation of in vitro antioxidant and antimicrobial properties, and effects on broiler performance

Context. Dietary supplementation with phytobiotics may form part of an alternative strategy to the use of antibiotics as growth promoters in the poultry industry. Essential oils of rosemary (Rosmarinus officinalis L.) may have antimicrobial and antioxidant properties.Aims. The aims were to evaluate in vitro characteristics of non-encapsulated and encapsulated rosemary essential oils, and to investigate their effects on growth performance, intestinal morphology and microbial population in broiler chickens. Methods. Essential oil main components were determined, and the minimum inhibitory concentration and 2,2-diphenyl-1-picrylhydrazyl radical assay methods were applied for determination of antimicrobial and antioxidant activities, respectively. In an in vivo study of performance, 1-day-old male chicks (n = 420) were randomly assigned to seven dietary treatments with five replicates of 12 birds in a completely randomised experimental design. Treatments were control (basal) diet, and basal diet supplemented with chitosan (encapsulating agent) at 150 mg/kg, encapsulated and non-encapsulated rosemary essential oils at both 150 and 300 mg/kg, and the antibiotic flavophospholipol at 650 mg/kg. Key results. Non-encapsulated essential oil had stronger antioxidant activity than the encapsulated form (IC50 values 0.969 and 1.879 mg/mL, respectively). Non-encapsulated essential oil had greater antimicrobial effect against Escherichia coli, whereas the encapsulated form was more effective against Staphylococcus aureus. During the whole growing period of the in vivo study, supplementation with different levels of non-encapsulated or encapsulated essential oils significantly (P < 0.01) improved bodyweight gain and feed conversation ratio compared with control and antibiotic diets. Furthermore, feed intake in birds receiving essential oils (150 or 300 mg/kg) was lower (P < 0.01) than in other groups. Villus height was increased (P < 0.01) in birds supplemented with essential oils compared with all other treatments. Ileal coliform count was lower in birds supplemented with non-encapsulated essential oil at 150 mg/kg than in birds fed the control diet. Conclusion. Use of non-encapsulated rosemary essential oils at 150 mg/kg is recommended. Encapsulation did not provide additional benefits for most parameters. Ltions. Rosemary essential oils offer a potential replacement to conventional antibiotics in poultry nutrition, reducing the spread of antibiotic-resistant bacteria and presence of antibiotic residues in animal tissues.