Mode of synergistic action of hydrolyzable tannins and probiotic microorganisms on the growth performance, immunology, ileal histomorphology and microbiology in broiler chickens

The current study was conducted to evaluate the synergistic effects of three concentrations of either hydrolyzable tannin (HT; g/kg) or probiotic microorganisms (PM; g/kg) on the intestinal microbiota, histomorphology, immunological responses, and growth performance of broiler chickens. A total of 1404 one-day-old female broiler chickens were randomly assigned to nine experimental treatments with six replicates and each pen as a replicate contained 26 chickens. Treatments consisted of a 3 x 3 factorial arrangement, consisting of 0, 0.75, and 1.5 g HT/kg of diet (0 HT, 0.75 HT, and 1.5 HT) and 0, 0.1, and 0.2 g PM/kg of diet (0 PM, 0.1 PM, and 0.2 PM). The results showed that dietary inclusion of 0.75 HT + 0.1 PM resulted in the greatest average daily weight gain (ADWG) with improved feed conversion ratio (FCR), increased immunoglobulin G, immunoglobulin M, and total antibody titers against sheep red blood cell, increased ileal villi length (VL), and the heaviest relative weight of bursa of Fabricius (P < 0.05). Broiler chickens fed only with 0.75 HT benefited from the largest ADWG, smallest FCR, heterophils to lymphocytes ratio (H:L), ileal E. coli count, and greatest ileal villi length to crypt depth ratio (VL:CD), and immunoglobulin G, immunoglobulin M, and total antibody titers against sheep red blood cell (P < 0.05). Nevertheless, feeding 1.5 HT led to a decrease in ADWG, humoral immune response, liver relative weight, VL:CD, and an increase in FCR, the numbers of goblet cells, and H:L (P < 0.05). Similarly, dietary administrations of 0.2 PM caused the greatest numbers of monocytes, intestinal Lactobacillus, lamina propria lymphoid follicles, goblet cells, and the lowest H:L as well as pH of the ileal content, and E. coli enumeration (P < 0.05). In general, the present findings would indicate that although dietary inclusion of 0.2 PM improved the growth performance and either microbial or histological indices at the ileum of broiler chickens, feeding 0.75 HT + 0.1 PM, without an adverse effect on gut microbiota, manifested the best synergistic effects on the growth performance of broiler chickens via improvement of humoral immunity, relative weights of lymphoid organs, and the ileal absorptive area.