Fig. 1

Growth performance and immune activity of broiler chicken under the feed-additive regimens of antibiotics, probiotics, and the control. Average daily gain (ADG; n = 6; a), average daily feed intake (ADFI; n = 6; b), and feed conversion ratio (FCR; n = 6; c) were compared among the three treatment groups during the various periods. “*”: significantly changed (p < 0.05). The average daily gain (ADG) was measured per chicken, while the average daily feed intake (ADFI) and the feed conversion ratio (FCR) were measured per 15-broiler pen (six pens in each group). d Comparison of three immune organ indexes from thymus gland, bursa, and spleen (n = 6), which were measured at the last day of the 42-day regiment. Two chickens were randomly selected from each replicate of each group and sacrificed for the measurements. e Comparison of serum IgG (n = 6) and intestinal SIgA (n = 6) levels among the three groups on day 14 and day 42. The two values were measured on a per chicken basis, and 12 of the chickens from each pen were randomly selected for the inter-group comparison