Effects of Yarrow (Achillea millefolium) Essential Oil Compared with Growth Promoter Antibiotic and Probiotic on Growth Performance, Meat Quality, and Immune Response of Broiler Chickens

Application of growth-promoting antibiotics in poultry nutrition improves growth, feed intake, feed conversion ratio and reduces mortality. But, due to their persistent effects and increased drug resistance to pathogenic bacteria and the transmission of bacteria to humans through the food chain, the European Union banned their use. One of the natural alternatives is medicinal plants. Because plant products for reasons such as availability, ease of use, reduction of side effects, antibacterial and antioxidant properties, were used to treat some diseases in humans and animals. Among these medicinal plants we can mention yarrow with the scientific name of Achillea millefolium. This plant in addition to high antimicrobial and antioxidant properties; has antifungal properties, stimulates appetite, improves digestion and feed intake, improves the condition of the gastrointestinal tract, etc. This plant also accelerates digestion and shortens the passage of food through the gastrointestinal tract by increasing bile production and enzymatic activity. On the other hand, probiotics are living microorganisms of a nonpathogenic and nontoxic in nature that improve gastrointestinal health and improve performance in birds by improving intestinal microbial balance. According to these cases, this study was performed to evaluate the effect of yarrow essential oil in comparison with a growth-promoting antibiotic and probiotic on performance of broiler chickens. A total of 200 day-old male broiler chicks (Ross 308) were studied in a completely randomized design with five treatments, and four replicates. Experimental diets were: 1) basal diet (control), 2 and 3) basal diets supplemented with 100 and 200 mg/kg of yarrow essential oil, respectively, 4) basal diet supplemented with 200 mg/kg probiotic, and 5) basal diet supplemented with 500 mg/kg antibiotic (flavophospholipol). Body weight and feed intake were measured at the end of each growing period and were used to calculate Performance parameters such as body weight gain, and feed conversion ratio. At the end of the experiment, one bird per each replicate was slaughtered for meat quality tests, including measurements of TBARS, pH, water holding capacity, dripping loss and antibody titer. For TBARS, the amount of fat oxidation of the sample was measured by measuring the amount of malondialdehyde and the microtiter hemagglutination method was used to determine the antibody titer produced against sheep erythrocytes. During the whole experimental period, birds received yarrow essential oil at 100 mg/kg diet, showed significantly higher body weight and lower FCR compared to the control group(P <0.05).  The lowest feed intake was observed in birds that were fed from the level of 200 mg/kg of yarrow essential oil. However, this effect was significant only in comparison with antibiotic treatment, which showed the highest feed intake (P <0.05). Different results have been reported in this regard which can be related to the type of plant, the amount of active ingredients, the level of the medicinal plant used and the interactions with other components of the diet. The TBARS index, indicating lipid oxidation of meat, in chickens fed with different levels of yarrow essential oil and probiotic were lower compared to the control group and antibiotics. In vitro, researchers have shown that plant essential oils, such as yarrow alkaloids, can reduce free radicals and can be a good alternative to synthetic antioxidants. Also in the study of using a mixture of plant extracts increased the concentration of phenols and decreased the amount of TBARS in the meat of broilers. pH, water holding capacity, dripping loss and cooking loss were not affected by the dietary treatments. The antibody titer against sheep red blood cell (SRBC) was lower in the control group in compare to those fed different levels of yarrow essential oil. In some studies, yarrow has increased humoral immunity with its antimicrobial and antioxidant properties; but, the amount used and the concentration of plant material were also effective. Based on the results, the use of 100 mg/kg yarrow essential oil increased body weight, improved feed conversion ratio and also increased antibody titer at 42 days of age. On the other hand, the TBARS index in chickens fed with different levels of yarrow essential oil was lower in compare to control group. Finally, according to the results, it can be concluded that the use of yarrow essential oil at the level of 100 mg/kg can be a good substitute to antibiotics in poultry nutrition.