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چکیده
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This study was performed to investigate and compare the effect of different feed additives on growth performance, slaughter parameters, immune response, leukocyte profile and blood biochemical parameters of broilers. A total of 350 day-old male broiler chickens (Ross 308) were randomly assigned to seven treatments with five replicates each (10 chickens per replicate). Chickens were fed either a corn-soybean meal basal diet (control) or the basal diet supplemented with 5 g/kg black seed (BS1), 10 g/kg black seed (BS2), 20 g/kg black seed (BS3), 1 g/kg probiotic (Pro), 1 g/kg prebiotic (Pre) or 1 g/kg synbiotic (Syn). Average body weight gain (BWG), feed intake (FI) and feed conversion ratio (FCR) of broilers were determined during the starter (0 to 10 days), grower (11 to 28 days) and finisher (29–42 days) periods, and also for the total experimental period (0–42 days). Three chickens per replicate were randomly selected to evaluate a cutaneous basophil hypersensitivity reaction to phytohaemagglutinin-P (PHA-P) on days 35 and 36. Blood samples (2 samples per replicate) were taken for measuring antibody responses (days 28 and 42), and also for hematological and biochemical analysis (day 42). After 6 weeks, BWG was higher for Syn-fed chickens compared with control group (P<0.05). From 0 to 42 days, FCR was improved by diets BS2, Pro and Syn by approximately 6.3, 6.3 and 7.3% respectively, compared to that of the control group (P<0.05). The toe web swelling, as cell mediated response to PHA-P, in the chickens fed diets BS3 and Syn was respectively 30.5 and 27.1% greater than in chickens fed control diet (P<0.05). All diets, except diets BS1 and BS2, increased primary antibody response against sheep red blood cell (SRBC) at 28 days (P<0.05). Moreover, broilers fed diets BS3, Pro and Syn showed the higher secondary anti-SRBC titers and lower plasma triglyceride, cholesterol and low-density lipoprotein cholesterol levels at 42 days (P<0.05). Other measured parameters, incl
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