Effects of synbiotic on the intestinal morphology and humoral immune response in broiler chickens

The objective of this study was to investigate the effects of synbiotic on humoral response to Newcastle disease vaccine and intestinal morphology. A total of 108 one-d-old fast-growing broiler chickens (Ross 308) were allocated to pens, then, pens were assigned to 1 control and 2 treatments with 3 pens per treatment and 12 chickens per pen. Chickens were reared at standard condition for 6 week and provided a standard basal diet and diets supplemented with 0.1 or 0.2% synbiotic. On d 8, 22, 32, and 42, 12 chickens from each treatment were randomly selected and blood samples were collected. Antibody response was measured by the hemagglutination inhibition technique. On d 22, and 42, 12 chickens from each treatment were killed and 3 segments of intestine were dissected for evaluation of intestinal morphology. Antibody titers were increased in chickens fed the diet supplemented with synbiotic (P<0.05). Antibody level in chickens fed the diet supplemented with synbiotic increased at d 22, 32, and 42 compared to d 8. Amount of antibody was increased at d 32 compared to other day in chickens fed 0.2% synbiotic supplement (P<0.05). Antibody level was progressively reduced in the control group at d 22, 32, and 42. Duodenal villus height was greater in both treatments than their controls (P<0.05). Duodenal villus surface area was also greater in chickens fed 0.1% synbiotic supplement than controls at d 22, 32, and 42 (P<0.05). Jejunal villus width and surface area were lower in chickens fed 0.2% synbiotic supplement than controls on d 22 and 42 (P<0.05). Ileal villus height was lower (P<0.05) in chickens fed 0.2% synbiotic supplement than controls on d 42, while the villus width and surface area were only greater (P<0.05) in chickens fed the diet supplemented with 0.1% synbiotic. The sum of measured villus surface area in 3 intestinal parts was greater only in chickens fed 0.1% synbiotic supplement on d 42 (P<0.05). Villus types changed from leaf and tongue to convoluted and ridge shapes in both treatments on d 22 and 42 (ileum, 0.1 and 0.2% synbiotic) and 32 (jejunum, 0.2% synbiotic) compared to their controls (P<0.05). It is concluded that synbiotic had beneficial effects on antibody production, and antibody levels in chickens fed synbiotic supplement were maintained or increased during rearing. In intestine, only 0.1% synbiotic had positive effect on intestinal morphology.