Impact of oregano essential oil on production data and lipid oxidation parameters in broiler chickens

In a study with male broiler chickens the impact of dietary oregano essential oil on performance data and on the susceptibility of abdominal fat, fresh and stored breast muscle tissue to lipid oxidation was examined. Four diets supplemented either with oregano essential oil in two levels (22.5 mg (OL) and 90 (OH) mg kg feed ), 40 mg α-tocopheryl acetate (VE) or without these additives (NC) were examined. In abdominal fat the best oxidation stability (investigated by the Rancimat method) was found in VE, differing significantly from NC, OL and OH. Just as well in fresh breast muscle lowest susceptibility to lipid oxidation (in terms of thiobarbituric acid reactive substances) could be observed in VE. During refrigerated storage (3, 6 and 9 days at 4° C) VE and OL showed similar protective effects on lipid oxidation in breast muscle, whereas OH probably acted in a pro-oxidative manner. With regard to production data dietary oregano essential oil (OL) showed a slightly positive effect on feed intake and growth performance. Introduction Oregano (origanum vulgare) belongs to the Lamiaceae family and is a typical spice of the “Mediterranean cuisine”. Next to other ingredients it contains up to 4 % of essential oils, primarily the two isomeric phenols thymol and carvacrol to variable amounts. The latter depends on different factors such as climate, habitat, harvest conditions or part of the plant from which the oil is extracted. Due to their biological effects such as anti-microbial, antioxidative or probably appetite stimulating properties, essential oils have gained much attention in investigations with the objective to replace antimicrobial growth promoters and synthetic feed additives in general by natural products which might be more acceptable to consumers. Whereas a bigger part of these investigations are showing auspicious results in in vitro studies, there is a lack of adequate and consistent results from animal studies (Rodehutscord and Kluth, 2002). For this reason further clarifications are required. In the present investigation with broiler chickens the effect of dietary oregano essential oil compared to α-tocopheryl acetate on the susceptibility of abdominal fat and breast muscle meat to lipid oxidation was studied. Furthermore a possible impact of oregano on feed intake, growth and metabolism data was examined. Materials and Methods 72 day-old chickens (Ross PM3) housed in metabolism cages in groups of 18 animals each were randomly assigned to 4 dietary treatments: basal diet NC (without α-tocopheryl acetate supplementation), basal diet supplemented with 40 mg α-tocopheryl acetate (VE), 22.5 (OL) and 90 (OH) mg oregano essential oil kg feed respectively. The basal diet mainly containing maize (30 %), wheat (30 %), soy bean meal (27.5 %) and rape oil (5 %) was formulated to contain all nutrients required by broilers. The oregano essential oil available was in a fine powder form, commercially known as ROPA Green (ROPAFARM GmbH, Westerstede / Germany) and α-tocopheryl acetate as ROVIMIX E-50 adsorbate (DSM Vitamins Ltd, Basel / Switzerland). After one week the treatment groups were divided into three cages with 6 animals each. Feed and water were provided ad libitum. Group body weight, feed intake and water consumption were recorded weekly. Representative feed samples and excreta samples from each cage were taken on 3 consecutive days during the 3 and 5 experimental week in order to estimate energy and nitrogen utilization according to the indicator method using acid