Abstract: The aim of this study was to evaluate the effects of probiotic bacteria, Lactobacillus delbrueckii subsp. bulgaricus (PTCC 1332) on the humoral immune response of the rainbow trout, Oncorhynchus mykiss. The bacterium was administered at 3 different doses, 5×105 (LAB5), 5×107 (LAB7) and 5×109 (LAB9) CFU g 1 of feed to the rainbow trout (110 g initial mean weight) for 4 weeks and the feed was changed to un-supplemented diet for 2 weeks after. During the trial, water quality parameters such as temperature, dissolved oxygen, pH, NH4+ and NO2- was measured. Blood and intestinal samples were taken from the onset of feeding supplemented diets at 10, 20, 30 days after LAB feeding and 2 weeks after feeding withdrawal (45 days). The humoral immune response of the fish was evaluated during the experimental period. During the LAB feeding period, L. delbrueckii sp. bulgaricus persisted in the fish intestines in the high numbers, but the number of LAB rapidly decreased in the intestines after changing to the un-supplemented diet. In comparison to untreated control fish, the alternative complement activity in the serum was found to be significantly (p< 0.05) greater in all LAB groups especially in the LAB7 group 20-30 days after feeding. The lysozyme activity of the treatment groups were increased significantly (p< 0.05) 20 days after feeding and the LAB9 group had higher lysozyme activity than all groups. The total plasma immunoglobulin level was increased significantly (p< 0.05) in the fish groups that received the L. delbrueckii sp. bulgaricus, especially in the LAB7 group 10 days after feeding. The results showed that the humoral immune response was enhanced by the using of probiotic bacteria.
Amir Tukmechi , Ahmad Morshedi and Nowruz Delirezh , 2007. Changes in Intestinal Microflora and Humoral Immune Response Following Probiotic Administration in Rainbow Trout (Oncorhynchus mykiss) . Journal of Animal and Veterinary Advances, 6: 1183-1189.