The aim of the study was to investigate the influence of dietary supplementation of various levels of milk thistle (MT) on growth performance, oxidative stress, and immune response of natural summer stressed broilers. A total of 120 1-day old broiler chicks were distributed into 4 treatments: MT-0 (control), MT-5 (5 g/kg of MT), MT-10 (10 g/kg of MT), and MT-15 (15 g/kg of MT), each with 3 replicates having 10 birds per replicate. Results showed that overall feed intake, body weight, feed conversion ratio (FCR), and dressing percentage were significantly (P < 0.5) higher with MT-15 as compared with the other experimental treatments. Unlikely, significantly lower level of malondialdehyde (MDA) was observed with MT-15. Dietary supplementation of MT had no significant effect on paraoxonase activity in broiler. Antibody titer was significantly (P < 0.05) higher with MT-15 while it was lower with the control treatment. It was concluded that dietary supplementation of MT at the rate of 15 g/kg can significantly lower the negative effects of natural summer stressed broilers.
Keywords: Growth performance; Immune response; Milk thistle; Oxidative stress.