Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 2/21/2003
Publication Date: 2/21/2003
Citation: Shoemaker, C.A., Klesius, P.H., Lim, C.E., Yildirim, M. 2003. Feed deprivation in a controlled environment increased susceptibility of channel catfish to disease. Catfish Farmers of America Research Symposium.
Technical Abstract: Withholding feed has been suggested as a possible strategy to manage infectious disease of catfish. We conducted a series of experiments to examine the effect of feeding regimens on the resistance of channel catfish to Edwardsiella ictaluri and Flavobacterium columnare and to measure changes in physiological and immune parameters. Four week feeding regimens of the E. ictaluri studies which included non-fed (NF), fed once daily to satiation (FD), fed every other day to satiation (FEOD) and fed once daily to satiation during the fourth week only (FD4) were assigned to 60-70 fish in triplicate aquarium. At the end of week 4, fish were split into 6 groups of 25 fish and challenged with E. ictaluri by bath immersion. After challenge, fish in three aquaria of the same treatment were continued on the same feeding regimen, those of the other three aquaria of the NF treatment were switched to FD, whereas the remaining treatments were switched to NF. Mortality due to ESC was highest for the NF/NF fish (100 %) and was followed by the NF/FD fish (98.7%). Fish FD or FEOD and continued on these feeding regimens had significantly lower (P < 0.05) mortality (25.3 and 32.0 %, respectively). Studies on F. columnareincluded feed deprivation of 19-g catfish for 3, 7 or 10 days in the first trials. Fish not fed for 7 or 10 days and maintained in the absence of feed following challenge had significantly higher (P < 0.05) mortality to F. columnare infection (70 and 100 %, respectively) than fish NF for 3 days (11.7 %), and fish FD for 3 (18.3 %), 7 (11.7 % ) or 10 (11.7 %) days prior to and throughout the challenge period. In a more recent study using 36-g catfish, we documented changes in the fish following NF, FD and FEOD for 4 weeks prior to and 2 weeks following challenge (week 6). Significantly lower (P < 0.05) blood glucose (39.5, 40.3 and 46.3 mg/dL) and liver glycogen (1.7, 1.8 and 1.9 mg/g) was seen in the NF fish at week 2, 4 and 6, respectively, as compared to values of FD (67.5, 92.8 and 93.41 mg blood glucose/dL and 46.5, 52.6 and 41.9 mg liver glycogen/g at 2, 4 and 6 weeks, respectively) and FEOD (82.8, 85.5, 77.3 mg blood glucose/dL and 45.1, 51.4, 41.4 mg liver glycogen/g at 2,4 and 6 weeks, respectively) fish. Mortality in the NF fish due to F. columnare (78 %) was significantly higher (P < 0.05) than mortality in the FD and FEOD treatments (0.0 and 1.7 %, respectively). Channel catfish deprived of feed for 4 weeks exhibited lower blood glucose and liver glycogen than catfish FD and FEOD. Our results indicate that in the absence of natural food, fish that were NF prior to and following challenge were susceptible to E. ictaluri and F. columnare. Feed deprivation (starvation), a form of chronic stress resulted in reduced immune function and/or disease resistance in channel catfish.