Effect of adding Mentha piperita powder on performance, immune system, and blood parameters of broilers under ascites induction conditions

Increasing the growth rate has made broilers susceptible to environmental stresses and has reduced the bird's ability to confront oxidative stresses and has increased the incidence of metabolic diseases, especially ascites syndrome. Oxidative stress is caused by an imbalance between the production of free radicals in the body and antioxidant defense mechanisms and it is one of the effective factors in increased pulmonary blood pressure. Peppermint with the scientific name of Mentha piperita stimulates growth and immune response and in addition to antibacterial and antifungal effects, it has antioxidant properties. The most important constituents of this plant are menthol, menthone, and methyl acetate, which in low concentrations, dilate blood vessels and reduce the production of malondialdehyde. This experiment was performed to evaluate the effects of adding peppermint powder on the performance, immune response, and blood parameters of broilers under ascites induction conditions.

After preparing the dry powder of the peppermint plant, the amount of essential oils was extracted using a Clevenger apparatus, and the active substances, volatile and phenolic compounds were measured using a GC-Mass spectrometry. 600 male Ross broilers were used in a completely randomized design with six treatments, five replications, and 20 chicks per experimental unit from 10 to 42 days of age. Diets were adjusted based on the nutritional needs of the Ross strain. Experimental treatments were included: 1) positive control (without induction of ascites and without adding the antioxidant), 2) negative control (induction of ascites without adding the antioxidant), 3) vitamin C (induction of ascites with 400 mg/kg diet), 4) vitamin E (induction of ascites with 200 mg/kg diet), 5) and 6) levels of one and two percentages of peppermint powder with induction of ascites, respectively. To induce ascites, chickens were given water containing 1,200 mg/L sodium (3 g/L NaCl) from day 15 of the experiment. During the experimental period, performance traits (body weight and feed intake) were recorded and on day 38 of the experiment, two blood samples from each replication were taken to measure blood parameters (glucose, total protein, albumin, cholesterol, triglyceride, high-density lipoprotein (HDL) and low-density lipoprotein (LDL)). At the end of the experiment, two chicks of each replication were slaughtered to measure immune organs. The ratio of the right ventricle to the total ventricle (RV / TV) was also considered to be an anatomical indicator of ascites. To measure the humoral immune response, 10 % SRBC suspension solution was injected intravenously, and to measure the cellular immune response, 0.1 mL of phytohemagglutinin was injected between the toes of the bird's right toes.

Laboratory analysis of peppermint powder showed that the most active compounds and substances included menthol with 46.21 % and dihydrocarole acetate with 16.19 %. The total essential oil content of peppermint was measured as 1.1 %. Results showed that body weight gain and feed conversion ratio decreased significantly under the ascites induction (P<0.05). The use of antioxidant compounds of vitamin C and vitamin E, as well as peppermint powder at the level of one percent, led to their improvement (P<0.05). Feed intake was not affected by experimental treatments. The weight of the spleen and bursa of Fabricius as a percentage of live weight was not affected by experimental treatments. The ratio of the right ventricle to the total ventricle (ascites index) showed a significant tendency (P = 0.08) and the ascites index was relatively improved as a result of using antioxidant vitamins and peppermint powder. Blood parameters were not affected by experimental treatments. Induction of ascites decreased cellular immune response (PHA) (P<0.05), and antioxidant treatments, especially vitamin C, improved it. Humoral immune response was not affected by experimental treatments. The role of plant compounds as natural growth stimulants in broiler feed has been proven, although their growth stimulation mechanisms are still unclear. Medicinal plants have active aromatic compounds and they have beneficial effects on gastrointestinal health and bird performance. The effect of antioxidants on reducing the incidence of ascites is due to the elimination of free radicals, reduced blood density, and reduced resistance to pulmonary blood flow. Many of the active substances in medicinal plants prevent lipid peroxidation and improve bird performance by scavenging free radicals or by activating antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. The effectiveness of plant materials used in feeding broilers depends on factors such as the composition and level of plant material added to the diet, bird genetics, diet composition, and farm management.

‌ In general, the results of this study showed that the use of antioxidant compounds, especially vitamin C has a more effective role in improving performance, and the level of one percent peppermint powder in the diet can be used as an effective antioxidant compound in ascites syndrome.