Potential use of probiotic- and triherbal extract-enriched diets to control Aeromonas hydrophila infection in carp.

This study reports the effect of probiotic- and triherbal extract-enriched diet on Cyprinus carpio (52 +/- 2 g, n = 250) inoculated intramuscularly (50 microl) with Aeromonas hydrophila (1.8 x 106 CFU ml(-1)). On Day 6 post-infection, the fish were divided into 4 groups and fed with the basal diet (IU) or with diets supplemented with triherbal extract (H), Sporolac (S) or Lactobacillus (L). A fifth group of non-infected fish fed with the basal diet was used as a control. Haematology and immunology parameters were measured in Weeks 1, 2 and 4. In the H, S, and L groups, white blood cell levels were significantly increased (p < 0.05) throughout the experimental period. In the H and S groups, red blood cell and haemoglobin levels decreased significantly (p < 0.05) in Weeks 1, 2 and 4. In all the diet groups, the haematocrit and mean corpuscular volume did not differ significantly (p > 0.05) in Week 1, and these values remained near those of the control in Week 2. The S and L groups did not exhibit significant changes (p > 0.05) in glucose, and cholesterol levels in Weeks 2 and 4 compared to controls, and the L group also showed no change in total protein. Respiratory burst activity was significantly increased in Weeks 1 to 4 in the H, S and L groups. Serum-mediated killing of Escherichia coli was significantly increased in the L group in Weeks 1 to 4. Mortalities after A. hydrophila challenge were higher in the IU (85%) and H (50%) groups than in the S (45%) and L (35%) groups. Our results show that formulated probiotic-enriched diets can speed up the recovery of ulcerative dermatitis induced by A. hydrophila in carp.