Efficacy of Different Blends of Essential Oils on Growth Performance, Blood Metabolites, Gut Microflora, and Meat Quality of Broilers

The application of phytogenic additives in the form of essential oils have attracted considerable attention in poultry industry. An experiment was conducted to evaluate effects of the blends of essential oils (EO) isolated from some medicinal plants including savory, thyme, fennel and rosemary on performance, blood metabolites, intestinal microflora, and meat quality of broilers. Two hundred 1-day-old broilers were randomly allocated to 5 treatments with 4 replicates of 10 chicks. The dietary treatments included 1) NC (negative control; without EO), 2) PC (positive control; 300 mg commercial EO of oregano/kg diet), 3) SR (300 mg EOs of savory and rosemary/kg diet), 4) SRT (300 mg EOs of savory, rosemary and thyme/kg diet), 5) SRTF (300 mg EOs of savory, rosemary, thyme and fennel/kg diet). Neither PC nor combinations of EOs affected growth performance of broilers. Serum cholesterol reduced (P<0.05) by feeding the blend of EOs compared with NC. The lowest ileal Lactobacillus counts were observed in chicks fed diets supplemented with EO of oregano or SR (P<0.05). Dietary supplementation of oregano EO decreased (P<0.05) lipid peroxidation of thigh meat after 30 and 60 days of frozen storage compared with NC group. Broilers fed diets supplemented with EOs of oregano or SR had the lowest ileal Lactobacillus spp. counts probably due to their large amount of carvacrol contents which suppress growth and proliferation of Gram-positive bacteria. Contrary to blended EOs, oregano EO did not reduce serum cholesterol concentration, suggesting hypocholesterolemic effect of other compounds except carvacrol in EOs. The highest stability to meat oxidation was achieved in oregano EOs-fed broilers. This antioxidative effect was lower in treatments with less carvacrol contents