ffects of hydroalcoholic extract of Scrophularia striata in comparison with antibiotic, probiotic and a multivitamin and mineral supplement on growth performance and blood parameters of broilers

Many researches have been conducted to find suitable alternatives for antibiotics and were all looking for additives that could produce similar results in the control of infectious diseases, improving the growth performance and feed efficiency. Essential oils and herbal extracts are considered as one of the main sources of natural pharmaceutical compounds with anti-microbial and anti-inflammatory properties. In the study of Rostami et al. (2015), it has been shown that dietary supplementation with Scrophularia striata powder at the level of 0.8 % of diet improved performance and immune response of meat-type chickens when compared with antibiotic supplement. However, due to the lack of research about the influence of S. striata extract on broiler performance, this study was conducted to evaluate the effect of S. striata extract on male broiler growth performance, blood biochemistry and hematology, and to compare them with three feed additives (antibiotic, probiotic and vitamin E + vitamin C + selenium complex). A total number of 450 one-day-old male Ross 308 broiler chicks were divided into 30 groups of 15 chicks each (six treatments and five replicates per treatment). The six experimental treatments were as follows: corn – soybean meal basal diet with no additives (control diet) and basal diet containing salinomycin antibiotic, probiotic, vitamin E + vitamin C + selenium complex (VS, 200 mg/kg vitamin E and C and 0.3 mg/kg selenium), 200 and 400 mg/kg S. striata extract (SSE1 and SSE2). Feed intake (FI) and body weight gain (BWG) were recorded in each phase feeding periods as starter (0-10 d), grower (11-24 d) and finisher (25-42 d) and feed conversion ratio (FCR) was calculated. To study the effects of different treatments on blood biochemistry and hematology, blood samples of two birds from each replicate were collected from the wing vein at the end of experiment. 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. The red blood cell (RBC) and white blood cell (WBC) counts were determined by a hemocytometer method using Natt–Herrick solution; hematocrit (packed cell volume) and hemoglobin values were measured by microhematocrit and cyanmethemoglobin methods, respectively (Kececi et al. 1998). To determine blood leukocyte profiles, 100 leukocytes per samples were counted by an optical microscope according to protocol described by Lucas and Jamroz (1961). The heterophil (H)/lymphocyte (L) ratio was then calculated. Biochemical parameters consisted of glucose, total protein, albumin, uric acid, triglyceride, total cholesterol, high-density lipoprotein cholesterol (HDL-C), very-low-density lipoprotein (VLDL-C), and low-density lipoprotein cholesterol (LDLC), lipase, calcium and phosphorus. All analyses were made using the commercial kits (Pars Azmoon, Iran) and a standard auto analyzer apparatus (Biotecnica, BT-3000, Rome, Italia), except for calcium. Calcium (Ca) value was determined by the atomic absorption spectrophotometer (Shimadzu AA-6200, Tokyo, Japan). The data were analyzed in a completely randomized design by ANOVA using the General Linear Model (GLM) procedure of SAS Institute. In the grower (days 11–24) and the overall (days 1–42) experimental periods, the FI of the SSE1 and SSE2 groups was lower (P < 0.05) compared with the control group. During the finisher (25-42 d) and whole experimental periods, the BWG and FCR were better (P < 0.05) in all experimental treatments compared with control group, where the birds fed diet SSE1 and SSE2 had the best BWG and FCR. The blood protein and albumin in the birds fed diet SSE2 was significantly higher than in birds fed the control and antibiotic diets. All diets, except diet M, decreased cholesterol and LDL levels compared with the control diet. Feeding SSE1 and SSE2 diets increased blood phosphorus concentration and blood lipase activity protein deposition; additionally, feeding SSE2 diet significantly increased blood calcium level. Furthermore, broilers fed the antibiotic and SSE2 diets had higher blood hemoglobin level and lower WBC counts compared with VS treatment (P < 0.01). The birds fed any of the diets, except diet SSE1, exhibited lower H/L ratio than those fed the control diet. The better BWG and FCR in broilers which fed 200 and 400 mg/kg S. striata extract reveals that the impact of phytogenic products on performance could be related to the presence of growth-promoting substances in these herbs. In general, an improvement in FCR of chickens when feeding herbal products has been proven in the majority of the studies recently reviewed by Brenes and Roura (2010), who indicated that in most researches the improvement in FCR comes as a result of decreasing in FI at a largely unaffected BWG. However, in this study S. striata extract-containing treatments not only decreased FI, but also increased BWG. Polyphenolic compounds inhibit the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA) enzyme; hence, the synthesis of cholesterol is inhibited. This action increases the LDL receptors at the surface of the hepatocytes and, as a result, accelerate LDL catabolism. HMG-CoA reductase inhibitors, reduce blood LDL, and to a lesser extent, blood triglyceride concentrations and slightly increase HDL concentrations (Barreto et al., 2008). Monsef-Esfahani et al. (2010) discovered that the essential oils and extracts from S. striata contain quercetin, which have important antioxidant activity. Therefore, enhanced lymphocyte percentage and decreased H/L ratio by the SSE2 treatment, along with the cell protection against oxidative stress, seemed to contribute to the higher WBC count reported in this study. According to the results, the 400 mg/kg S. striata extract can be used as an alternative to antibiotics and other commonly used additives at the level of to the diet of broiler chickens.