علیرضا مجاهدطلب

The effects of different levels of Silymarin were studied on performance and immune responses in 288 one-day chicks (Cobb 500) in a completely randomized design with 6 treatments and 4 replicates and 12 observations per replicate. The treatment groups received 0 (Control), 160, 200, 240, 280 and 320 ppm of Silymarin in diet, respectively during days 3 to 42. Daily feed intake, daily body weight gain and feed conversion ratio (performance) were measured. The birds were immunized with sheep red blood cells (SRBC) on days 8 and 22 of age and serum antibody levels produced in response to SRBC were measured on days 21, 28, 35 and 42 by hemagglutination assay. Skin response to phytohemagglutinin-P (PHA-P) injected intradermally on day 16 were measured 24 and 48 h after injection. The results indicated that consumption of 200, 240, 280 and 320 ppm Silymarin reduced feed intake and feed conversion rate (P<0.05), but they did not affect on daily weight gain (P>0.05). The levels of 200, 240, 280 and 320 ppm Silymarin were increased total Anti-SRBC and IgG titer in experimental groups compared to control group (P<0.05), but IgM titer and skin response against PHA-P were not affected by Silymarin (P>0.05). It is concluded that the continuum consumption of 200, 240, 280 and 320 ppm Silymarin improved performance and increased humoral immunity in broilers.