Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 26, 2003
Publication Date: September 1, 2003
Citation: Shoemaker, C.A., Klesius, P.H., Lim, C.E., Yildirim, M. 2003. Feed deprivation of channel catfish, Ictalurus punctatus (Rafinesque), influenced organosomatic indices, chemical composition and susceptibility to Flavobacterium columnare. Journal of Fish Diseases. 27(9):553-561. Interpretive Summary: Feed deprivation (not feeding fish) has been suggested as a method to manage enteric septicemia of catfish caused by a Gram negative bacteria called Edwardsiella ictaluri. Little research has been conducted in the laboratory to determine if this management strategy is effective against other bacteria or if not feeding the fish results in fish being more susceptible to disease. In a previous study, we found that not feeding fish for 7-10 days resulted in fish becoming susceptible to Flavobacterium columnare, another important Gram negative pathogen of channel catfish. This study was conducted to evaluate the effect of not feeding, feeding once every other day or feeding daily to apparent satiation (i.e., until fish no longer accept feed) on organosomatic indices (e.g., hepatosomatic index or liver weight divided by fish weight X 100), hematology, blood glucose and liver glycogen and proximate composition of the fish (i.e., moisture, protein, ash and lipid). Following 28 days on the selected feeding regimen, susceptibility of channel catfish to F. columnare was determined. Blood glucose, liver glycogen and hepatosomatic index were found to be sensitive indicators for channel catfish deprived of feed. Blood glucose and liver glycogen levels around 40 mg/dL and 2 mg/g, respectively, indicated starvation in juvenile channel catfish. Moreover, feed deprived fish were susceptible to F. columnare infection. Our results suggest that in the absence of natural food, juvenile channel catfish should be fed at least once every other day to apparent satiation to maintain normal physiologic function and improve resistance to F. columnare.
Technical Abstract: Withholding feed has been suggested as a strategy to manage infectious disease of channel catfish, Ictalurus punctatus (Rafinesque). In a previous study, we demonstrated that deprivation of feed for as little as 7 days reduced innate resistance of catfish to Flavobacterium columnare. This study was conducted to evaluate the effect of feeding regimens [non-fed (NF), fed once every other day to satiation (FEOD) and fed once daily to satiation (FD)] on organosomatic indices, physiologic changes and susceptibility of channel catfish to F. columnare. Fish that were not fed (NF) for 2 and 4 weeks had a significant increase (P < 0.05) in gutted weight:wet weight ratio and decrease in other organosomatic indices (gut index (GI), mesenteric fat index (MFI) and hepatosomatic index (HSI). Hematology was not effected by feeding regimen except at week 4, when a significantly higher hemoglobin level was observed in the NF fish. Serum protein did not differ at week 2, but the level at week 4 of the NF fish (35.91 mg/mL) was significantly lower than that of the fish FD (41.77 mg/mL). Significantly lower (P < 0.05) blood glucose (39.5 and 40.3 mg/dL) and liver glycogen (1.7 and 1.8 mg/g) was seen in the NF fish at weeks 2 and 4, respectively, as compared to blood glucose and liver glycogen levels of fish FD (67.5 and 92.8 mg/dL and 46.5 and 52.6 mg/g at weeks 2 and 4, respectively) and FEOD (82.8 and 85.5 mg/dL and 45.1 and 51.4 mg/g at weeks 2 and 4, respectively). 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). Observations on blood glucose and liver glycogen showed the same trend of low values for NF fish following challenge (week 6). Blood glucose, liver glycogen, GI and HSI are sensitive indicators for channel catfish deprived of feed (NF) for 4 weeks. Blood glucose and liver glycogen levels around 40 mg/dL and 2 mg/g, respectively, are indicative of starvation in juvenile channel catfish. Moreover, NF fish were susceptible to F. columnare infection. Thus, it is suggested that in the absence of natural food, juvenile channel catfish should be fed at least once every other day to apparent satiation to maintain normal physiologic function and improve resistance to F. columnare.