the effect of eٍssential oil, prebiotic, probiotic and antibiotic on performance and immune response of broilers chickens.

in this research, we investigated the effects of medicinal plants, prebiotic and probiotic as alternatives to antibiotics on the growth performance, immune response and blood cholesterol in broilers. a total of 288 one- day-old broiler chicks (cobb 500) were randomly assigned to 6 treatments and replicated 4 times with 12 chicks per pen in a completely randomize design experiment in 6 wk. diet 1 was a negative control containing no antibiotics or growth promoters (nc). diet 2 was the positive control consisting of nc plus an antibiotic (15 ppm virginiamycin). diet 3 was nc and a blend of medicinal plants (450 ppm digestarom). diet 4 was nc to which probiotic (100 ppm protexin) was added. diet 5 was nc plus prebiotic (0.1 % immunowall). diet 6 was nc plus a combination of probiotic (100 ppm protexin) and prebiotic (0.1 % immunowall). the mortality rate and survival percentage were determined daily. body weight gain, feed intake and feed conversion ratio (fcr) were measured weekly. immune response against sheep red blood cells (srbc) and blood cholesterol were measured in d 27 and 41. body weight gain in the starter and grower period, feed intake in neither of periods, fcr in the grower period, bursa fabricius and spleen relative weight, primary immune response against srbc were unaffected by dietary supplementation of experimental treatments . the fcr was significantly improved during the starter period in broilers fed antibiotic and medicinal plants, and during total period in broiler fed antibiotic and prebiotic as compared to broilers receiving other treatments. feeding prebiotic increased secondary immune response against srbc compared with antibiotic group. serum total cholesterol in d 27 and 41 was significantly increased in broilers supplemented with antibiotic as compared to other groups. the results demonstrated that addition of the prebiotic to the feed as well as antibiotic had a significant effect on fcr at 42 days of age and might be used as suitable alternative to antibiotic.