Effects of using essential oil mixture in drinking water on growth performance, hematology and blood lipid profile of ostriches (Struthio camelus)

Ostrich industries have been recently developed in many countries around the world, especially for the production of meat due to its favorable fatty acid profile and low fat content as compared with other kinds of red meat (Angel 1996). Modern strategies in ostrich production are improving health status and consumers’ requirements and also promoting their growth performance. In recent years, special attention has been paid to the use of herbal products, especially essential oils, in poultry diets as natural alternatives to antibiotic growth promoters. In addition to growth promoting effects of these compounds (Windisch et al. 2008; Brenes and Roura 2010), they can stimulate immunity (Habibi et al. 2014). Essential oils as a growth stimulant play an important role in improving health in different species of poultry; however, no specific study has been done regarding the dietary inclusion of herbal products in the ostrich diets. In this study, the effects of different levels of essential oil (EO) mixture supplement (containing an equal level of peppermint, eucalyptus, fennel and thyme) were examined on growth performance and hematological and biochemical parameters in African domestic ostrich chickens from ages 5 to 7 months.
Material and There were three treatments as follows: control (without essential oils), and levels of 200 and 400 mg EO per one liter of drinking water. A total of 18 ostrich chickens were used in this experiment (6 birds per treatment). The basal diet was formulated to meet nutrient requirements for the optimum growth conditions as recommended by Brand and Olivier (2011). Body weights and feed intake were recorded on a monthly basis for the 2-month duration of the trial. Feed conversion rate (FCR) was also calculated as the ratio of feed intake and body weight gain of respective groups. Blood collection was made from the wing vein from six birds per treatment by using vacutainer tubes, following about 12 h fasting to avoid diurnal influences. For hematological determination, blood samples were placed into EDTA anticoagulant-treated bottles (3 mg/2 ml) to prevent clotting. For serum biochemical analysis, blood samples were put into tubes containing a clot activator and serum gel separator. Samples containing EDTA were stored in ice box and immediately transferred to the laboratory for analyses. The other samples were centrifuged at 2,000×g for 10 min and frozen at −20°C until analysis. To determine blood leukocyte profiles, 100 leukocytes per samples were counted by an optical microscope. The heterophil to lymphocyte ratio was calculated as stress indicator. All data obtained from the trial were analyzed by General Linear Model (SAS Institute 2001), based on a completely randomized design. When, a significant probability value (P The level of 200 mg of EO significantly improved body weight gain and feed conversion ratio from 5 to 7 months of age (P0.05). Among different levels of EO, only 200 mg of EO mixture (peppermint, eucalyptus, fennel and thyme essential oils) in the drinking water improved growth and body weight gain compared to the control group, during the whole experimental period. There are conflicting effects on the use of herbal essential oils in other studies. For example, Khaksar et al. (2012) reported that the addition of thyme essential oils at 100 g/kg diet increased the weight gain of Japanese quail chickens during the 35-day period. In contrast, Kirkpinar et al. (2011) showed that body weight gain was not affected by the garlic essential oils or garlic and oregano essential oils mixture, and even the oregano essential oils caused weight loss in the broiler chickens. Improving the performance due to the application of herbal essential oils can be due to various factors, including the presence of active compounds in herbal essential oils, which have beneficial effects on digestive activity and improve the feed efficiency and also eliminate harmful microorganisms in the digestive system and feed products (Hashemi and Davoodi 2011). In a study in pigs, it has been reported that the blood hemoglobin concentration is not only dependent on the dietary protein level, but other nutrients, especially iron, are also effective on its concentration (Jolliff and Mahan 2011). Therefore, the increased absorption of nutrients, especially protein and iron, can be effective in increasing the blood hemoglobin level of broiler chickens receiving 200 mg essential oils. Increasing the absorption of nutrients, especially protein, has been reported by supplementation with vegetable essential oils in the other studies (Cao et al. 2010; Amad et al. 2011). Reducing the heterophil to lymphocyte ratio in the 200 and 400 mg of essential oils groups indicates that the addition of these essential oils to the drinking water of ostrich chickens has a positive effect on resistance to stress and even improving the immunity of the birds. Similar to the results of the current study, Hassan et al. (2011) reported that the addition of eucalyptus to the Japanese quail diet reduced the blood cholesterol and total lipids compared to the control group. The terpenoids from essential oil components extracted from the herbs have been reported to have a hypocholesterolemic effect (Elson and Yu 1994). This property is attributed to the inhibiting effect of these compounds on the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, which is the first enzyme in the pathway of cholesterol biosynthesis (Elson 1995).
In general, the addition of 200 mg EO to the drinking water of ostrich chickens was particularly effective in improving the growth, resistance to stress and cholesterol metabolism.