Intro
Medicinal plants and their products have attracted attention due to factors such as high economic value and low cost of their production, no destructive effects on the environment (organic drugs), few side effects compared to chemical drugs and antibiotics, and reduced relative resistance to disease agents. In recent years, these sources of medicine have attained a special value and place in the breeding, production and treatment of livestock and poultry (Tipu et al., 2006). In recent years, increasing consumer demand for healthy products has stimulated the production of meat products by reducing fat content and/or changing fat profiles. The fat composition of poultry meat may generally be manipulated using selected foods with specific nutritional properties (Sarica, 2003).Mammals are able to produce saturated and unsaturated fatty acids through simple precursors such as glucose and amino acids (Volker et al, 2001). Beneficial role of unsaturated fatty acids (PUFAs) such as linoleic acid (LA 18:2n-6), linolenic acid (α-LNA 18:3n-3), eicosapentaenoic acid (EPA 20:5n-3) and docosahexaenoic acid (DHA) 22:6n-3) includes the prevention of various human disorders such as breast cancer, severe cardiac arrhythmias, cardiovascular disease, rheumatoid arthritis, ventricular fibrillation and inflammatory diseases (Rudra et al., 2001). Some herbs and their products (extracts and essential oils) have natural effects such as tonic, anti-coccidial, anti-fungal, anti-parasitic, anti-flatulence and antioxidant (Tipu et al., 2006). Hernandez et al. (2004) showed that some plant extracts such as thyme (Thymus vulgaris) cause faster growth and improve intestinal digestion, starch digestibility, dry matter utilization of diets and carcass traits in broilers. Thyme extract has very high antioxidant properties that, in addition to reducing blood lipids, can play a role in inhibiting LDL oxidation. Carvacrol reduces plasma triglyceride concentrations. The use of carvacrol has been reported to stimulate the growth and proliferation of lactobacilli; lactobacilli play an important role in improving blood parameters and lowering serum lipids (Esteve-Garcia and Mack, 2000). Feed supplement with thyme essential oil can be considered as a useful natural supplement in the poultry industry to improve meat quality (Luna et al. 2010, Angelovicova et al. 2013). So, the purpose of the experiment was to evaluate the effects of thyme powder and its extract on profile of breast fatty acids in broiler chickens.
Methods
200 one-day chicks (45±2 g) were used in a total of 5 treatments and four replications and 10 chickens per replication for 42 days. All rearing processes were carried out under standard protocols (Azizi et al. 2020). The treatments were as below: Treatment 1: TE (0) + TP (0), aqueous extract of thyme (0 mg/kg) + thyme powder (0 mg/kg) Treatment 2: TE (50) + TP (150), aqueous extract of thyme (50 mg/kg) + thyme powder (150 mg/kg) Treatment 3: TE (50) + TP (250), aqueous extract of thyme (50 mg/kg) + thyme powder (250 mg/kg) Treatment 4: TE (100) + TP (150), aqueous extract of thyme (100 mg/kg) + thyme powder (150 mg/kg) Treatment 5: TE (100) + TP (250), aqueous extract of thyme (100 mg/kg) + thyme powder (250 mg/kg) The aqueous extract of thyme and thyme powder were made by Zarghani Pharmaceutical Company (Sabzevar, Iran). Diets were adjusted according to the poultry nutritional requirements table containing the minimum nutrients recommended in the Ross 308 strain feeding guide Manual (Table 1). Determination of breast meat fatty acid profile was performed by extracting 10 g of breast fat from 1 chicken in each treatment. At first, the fat samples were mixed well with 100 ml of methanol: chloroform (2:1) solution for 3 to 4 hours. The samples were then mixed with 25 ml of sodium chloride saturated solution in a decanter funnel. In the next step, the chloroform phase containing the fat was filtered through a filter paper impregnated with potassium anhydrous sulphate. The filtered sample was dried under vacuum in a rotary evaporator. An aliquot (10 mg) of extracted fat was stirred well with 2 ml of potassium hydroxide, 2 ml of methanol and 7 ml of n-hexane, then the resulting mixture centrifuged for 10 min. The sample was left for 5 min for the layers to separate. About one microliter of the supernatant was injected into the gas chromatograph to obtain the profile of fatty acids. The amount of each fatty acid was expressed as a percentage of total fatty acids (Tavakoli et al., 2020). The obtained data were statistically analyzed using analysis of variance by SAS statistical software (1982). The mean of treatments was compared at the 5 % probability level with Duncan's multiple range test. The design used in this experiment was completely random.
Results
The obtained data about percentage of fatty acids in breast muscle tissue is shown in Table 2. The results showed that the lowest percentage of three saturated fatty acids, myristic acid, palmitic acid and stearic acid were related to the level of thyme extract (100) and thyme powder (150) compared to the control group, and the highest percentage of saturated fatty acids was related to the level of thyme extract (50) and powder (250) compared to the control group, but the highest percentage of unsaturated fatty acids palmitoleic acid and cis-11,14-eicosadienoic acid was related to level thyme extract (50) and thyme powder (250). In addition, the highest percentage of cis-11,14,17-eicosatrienoic acid was related to the highest level of use of thyme powder and thyme extract.
Discussion
Lee et al. (2003) also found that the amount of linoleic acid in adipose tissue increased with thyme supplementation in the diet, which is consistent with the results of the present experiment. Lee et al. (2003) showed that the level of oleic acid in adipose tissue of broiler chickens decreases when fed a diet containing thymol, which does not correspond to the results of the present experiment. Youdim et al. (2000) also found that the content of palmitic and stearic acid in the brain of mice fed with thyme oil was lower than the control group, which is consistent with the results of the present experiment.