چكيده لاتين :
Introduction: Milk thistle (MT) (Silybum marianum L.), as one of the famous medicinal plant, belongs to Compositae family and is native for west and central Europe, and north of India (Zargari 1996). The plant is endemic for Iran too, and is grown in different parts of the country (Hassanloo et al. 2001). A mix of flavonolignans called silymarin forms the main bioactive component of this plant (Luper 1998). The content of silymarin in MT seeds collected from different zones of Iran varies from 6.9 to 27.1 mg/g of dry matter (Hassanloo et al. 2001). Supplementation of MT seed (Suchý et al. 2008, Rashidi et al. 2015) or silymarin (Schiavone et al. 2007) to the diet had no adverse effect on broilers performance. However, adding the seed and silymarin to aflatoxin contaminated diets prevented the deleterious effect of the toxin on broilers (Jamshidi et al. 2007, Chand et al. 2011). Silymarin has anti inflammatory and immunomodulatory effects which its mechanisms of action has been reviewed by Abenavoli et al. (2010). Addition of 200 mg/kg silymarin improved humoral immune response of broiler (Mojahedtalab et al. 2013). Reduction of cholesterol, increase of HDL-cholesterol (Rashidi et al. 2015), and decrease of alanin aminotransferas and aspartate amino transferase (Suchý et al. 2008) in broilers serum have been also revealed. In a previous study, MT seed, probably due to the presence of anti nutritional factors, decreased nutrients digestibility and performance of broilers (Khatami 2015). Hence, in this study the heated and crude MT seed was tested on broilers performance, some blood and humoral parameters.
Material and methods: A total of 256 one-day old broiler chicks (Ross 308) were randomly assigned to four treatments with four replicates and 16 birds each. The experimental treatments including zero (control), 0.4 percent crude, 0.4 percent heated and 0.8 percent heated MT seed were fed to broilers for a period of 42 days. MT seed was collected from Moghan zone, Ardabil province of Iran. Heat treatment of MT seed was performed using an oven (80 ˚C, 24 h). The experimental diets were formulated to meet or exceed the nutrient requirements for starter (0-10), grower (11-24) and finisher (25-42) phases (Table 1). The birds reared under standard conditions with free access to water and feed for 23 hours per day. At the end of each feeding phases, feed intake (FI) and weight gain (WG) of birds were recorded. Then using the data feed conversion ratio was calculated. To determine some blood serum biochemical parameters using the commercial kits (Pars Azmoon, Tehran, Iran), two birds (one male and one female) were bled from their wing vein on day 35. Two birds per cage were also injected intramuscularly with sheep red blood cells (SRBC) (2.5% suspension in PBS, 0.2 ml/ chick) at 35 days of age. Determination of total antibody titer (against SRBC) and resistant antibody to 2-mercaptoethanol (IgG) were done by hemagglutination assay following the blood sampling in 7th days after injection (Cheema et al 2003). IgM antibody level calculated from the difference between the total antibody and the IgG. The data were subjected to statistical analyses using the General Linear Model procedure of SAS software (SAS Institute, 2002). Duncan’s multiple range test was used to compare the significant difference between the means. Results and discussion: Through the starter period (0-10 days), adding 0.4 percent heated MT seed reduced WG and increased FCR of chickens (P<0.01). The birds on 0.8 percent heated seed had better WG that those on 0.4 percent heated seed (P<0.01). However, throughout the grower, finisher and whole experimental periods, none of performance parameters was affected by the treatments (Tables 2 and 3). The data obtained from the same level of heated and crude MT seed in starter phase indicated that heat treatment induced lower efficiency of consumed feed probably due to the decreased nutrients digestibility. In this period, the birds on 0.8 percent heated seed overcame their weight loss by increasing the FI. Due to the lack of available data on treated MT seed, the comparison of obtained data is difficult. However, no changes in growth performance of birds by MT seed, at the end of experiment, are in keeping with other studies (Suchý et al 2008, Rashidi et al 2015). Addition of 0.4 percent heated MT seed increased the concentration of serum albumin (P<0.05) and total protein (P<0.01). The concentration of glucose, total cholesterol and triglyceride was not affected by MT seed compared with control (Table 4). Reduction of serum albumen and total protein levels is considered as a sign for liver damage, for example, by exogenous toxins (Tedesco et al 2004, Sonkusale et al 2011). The supportive effect of MT on liver due to enhancing these parameters have been reported (Letsenco et al. 2008), as observed by 0.4 percent heated MT seed in this study too. Although the result on cholesterol was in line with Fani Makki et al. (2013), the reduction of cholesterol level has been shown by high level of MT seed (Suchý et al. 2008, Rashidi et al 2015). The activities of alanine aminotransferase and aspartate aminotransferase were decreased by all and some (0.4 percent of crude and 0.8 percent of heated) levels of MT seeds, respectively (P<0.01; Table 5). The reduction of these liver enzymes activity was in agreement with other studies (Suchý et al. 2008, Fani Makki et al 2014). Increased serum albumen and total protein in parallel to decreased liver enzymes could be denoted the supportive role of MT. The fact that has been extensively reviewed by Saller et al. (2007) and Abenavoli et al. (2010). Applying all levels of MT seed increased anti-SRBC (P<0.01) and IgG titers (P<0.05), while had no effect on IgM titer (Table 6). Such results have been also observed by Mojahedtalab et al. (2013). The findings indicated that the effect of MT seed on leucocytes did not influenced by heat treatment. Beside the direct effect of silymarin on leucocytes (Johnson et al 2003, Pradhan and Girish 2006), the immune modulatory effect observed in this study can be explained by anti inflammatory (Abenavoli et al 2010) and antioxidant (Das and Vasudevan 2006) effects of silymarin as well.
Conclusion: The results showed that bioactive components of MT are resistant to heat treatment (80 °C, 24 h). Appling MT seed in broilers diet had no positive effect on growth performance, but improved the performance of liver and humoral immunity.
