نوع مقاله : مقاله پژوهشی
1 دانشآموخته کارشناسی ارشد، گروه علوم دامی، دانشکده کشاورزی، دانشگاه گیلان
2 دانشیار، گروه علوم دامی، دانشکده کشاورزی، دانشگاه گیلان
3 استاد، گروه علوم دامی، دانشکده کشاورزی، دانشگاه گیلان
عنوان مقاله [English]
Introduction: Essential oils are volatile and concentrated liquids extracted from various parts of medicinal plants. In recent years, the use of essential oils in animal nutrition has gained interest as an alternative for antibiotic growth promoters. The main issue with using essential oils in poultry diets is the high volatility, which must be addressed by developing encapsulation techniques to preserve their efficacy. The purpose of the current experiment was to determine the effects of dietary supplementation of microencapsulated essential oil of Satureja khuzistanica on growth performance, oxidative stability of meat, and intestinal microflora of broilers.
Materials and methods: A total of 320 1-d-old Ross 308 chicks were studied in a completely randomized design with a 2×4 factorial arrangement of treatments. The factors were two administration forms of essential oils (free and microencapsulated) and four levels of dietary supplementation (0, 50, 100, and 150 mg/kg). The experiment consisted of eight treatments, four replicates, and 10 broilers per replicate. The essential oil of Satureja khuzistanica was microencapsulated using a 2% sodium alginate solution, which was mixed and homogenized before being transferred into a funnel and dropped into a beaker containing a 5% calcium chloride solution using a needle from a syringe. The beads were gently stirred for an hour to solidify. After one hour, the beads were filtered through a sieve and washed with distilled water. The beads were thoroughly rinsed before being air dried at 23 °C for 12 hours and kept in airtight containers. Body weight and feed consumption were monitored in pens weekly. From these data, average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were calculated weekly and throughout the entire rearing period. The European production efficiency factor (EEF) was also calculated for the whole rearing period. The minimum inhibitory concentration (MIC) of Satureja khuzistanica essential oil was determined by broth microdilution method for each of Escherichia coli, coliforms and lactobacillus bacteria. On day 42, two birds from each replicate were slaughtered and ileal samples were taken for microflora analysis. Total Escherichia coli, coliforms, and lactobacilli were enumerated in ileal digesta by the plate method using specific mediums. The thiobarbituric reactive substances (TBARS) assay was used to determine the oxidative lipid changes of the meat.
Results and discussion: The in vitro results demonstrated that the MIC of savory essential oil against gram-negative Escherichia coli and coliforms was higher (0.276) than its MIC for gram-positive lactobacillus bacteria (0.069). Throughout the in vivo study, the ADFI of broilers fed the diet with 150 mg/kg of essential oil was lower than the control (103.3 vs. 108.8; P<0.05). The ADG of broilers fed 100 mg essential oil/kg of diet was more than those fed 150 mg/kg (60.1 vs. 54.2; P<0.05). Broilers fed microencapsulated essential oil in their diet had a higher (P<0.05) EEF than those fed free essential oil. The addition of savory essential oil at 100 and 150 mg/kg of diet reduced (P<0.05) the lipid peroxidation in broilers meat stored for 60 and 90 days compared to the control. Lipid peroxidation of meat was lower (P<0.05) in broilers fed microencapsulated essential oil in the diet than those fed free essential oils. The addition of savory essential oil at different levels of 50, 100, and 150 mg/kg diet reduced the count of coliforms in the ileum compared to the control (P<0.05). Moreover, the data indicated that the addition of the essential oil at 100 and 150 mg/kg diet reduced the number of Escherichia coli (P<0.05). The bacterial count of coliforms and E. coli was lower in broilers fed microencapsulated essential oil than those fed free essential oil.
Conclusions: The results of this study showed that supplementation of Satureja khuzistanica essential oil in the diet improved broilers' performance and intestinal microflora. Microencapsulation of savory essential oil with alginate improved broiler growth performance, EEF, and increased the antibacterial activity of the essential oil which resulted in a further decrease of pathogenic bacteria. According to the findings of this study, 100 mg of microencapsulated savory essential oil per kg of broilers’ diet can be recommended due to its beneficial effects on performance, oxidative stability of meat, and intestinal microflora.