Effect of different levels of acid detergent fiber diets on growth performance, intestinal integrity and mucosal immunity of weaning rabbits

An experiment was conducted to investigate the effect of dietary acid detergent fiber (ADF) levels on the growth performance, intestinal integrity and mucosal immunity of weaning New Zealand rabbits. Three isoenergetic and isonitrogenous diets were formulated, containing ADF 150, 200 and 250 g/kg DM, respectively (treatment A150, A200 and A250, respectively. A200 was treated as the control group). One hundred and twenty New Zealand rabbits weaned at 35 d were allocated into the 3 treatments in accordance with their body weight. The average daily feed intake (ADFI) increased by 10.6% and 18.2% with increasing dietary fiber (P<0.001) over the whole fattening period, though the ratio of ADFI to average daily gain (ADG) of group A250 was impaired by 17.2% (P = 0.004) compared with group A200. The villous height/crept depth of group A250 in the jejunum and ileum was strikingly decreased by 41.7%, 68.6% (P = 0.002) and 37.9%, 40.6% (P = 0.014) compared with group A150 and A200. In the meanwhile, compared with group A200, the villous height of group A150 was decreased by 19.0% (P<0.001) in the jejunum. The sucrase activity in the jejunum and ileum were lowered by 22.1%, 22.6% (P = 0.005) and 13.7%, 17.9% (P = 0.011), respectively, for rabbits fed diet A250 compared with group A150 and A200, and maltase activity in the jejunum for the rabbits fed diet A150 and A250 were lowered by 14.4% and 34.2% (P = 0.001) compared with group A200. The production of cytokine interleukin-1β (IL-1β) and IL-6 of group A150 and A250 were 25.0%, 35.7% (P = 0.022) and 10.6%, 27.2% (P = 0.021) higher than that of group A200 in the jejunum, and 22.2%, 11.1% (P = 0.039) and 20.6%, 27% (P = 0.049) higher in the ileum. The production of cytokine IL-2 in the jejunum (P = 0.003) and ileum (P = 0.001) and of secretory sIgA (sIgA) in the jejunum (P = 0.033) were promoted with the increase of dietary fiber content. It was the first time to investigate the effect of dietary fiber on small intestinal immunity status. From the results we could come to the conclusion that the diarrhea of rabbits derived from small intestine inflammatory responses to some extent. The mucosal immunity status could be improved and subsequently growth performance of rabbits was promoted through increasing dietary fiber. The application of IL-2 might be an useful therapy for diarrheal rabbits.