Submitted to: Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/2/2005
Publication Date: 5/18/2005
Citation: Weber, T.E., Bosworth, B.G. 2005. Effects of 28 day exposure to cold temperature or feed restriction on growth, body composition, and expression of genes related to muscle growth and metabolism in channel catfish. Aquaculture 246:438-492. Interpretive Summary: Because cold temperatures decrease voluntary feed intake, channel catfish are fed infrequently or not fed at all during the winter. Likewise, cessation of feeding is used as a management practice during times of disease outbreaks in order to minimize fish mortality rates. It is well known that decreases in feed intake lead to decreased muscle growth and growth performance. However, the underlying physiological responses and changes in the expression of genes involved in muscle growth and development associated with the growth depression due to cold water temperature or feed withdrawal are not well known. We were also interested in the differences in these variables between the fish reared at cold temperature and the feed-derprived fish, given that the feed intkaes between the two groups would be comprable. Therefore, in this study we determined the effects of either cold water temperature or feed deprivation for 28 days on the growth performance, physiological variables, and the expression of genes involved in muscle growth and development. It was found that either exposure to cold temperature or feed deprivation decreased fish growth performance, but feed deprivation decreased growth performance to a greater extent than did cold water temperatures. Furthermore, cold temperature increased the expression of each of the genes measured on one or more occasion. Likewise, cold temperature increased the plasma concentration of the stress hormone, cortisol. These findings indicate that while both cold water temperatures and feed deprivation decrease fish growth performance, different physiological and genetic mechanisms are induced in each case.
Technical Abstract: Cold temperature decreases feed intake and growth of channel catfish, but the physiological and molecular mechanisms associated with the growth depression remain unknown. Therefore, an experiment was conducted to determine the effects of a 28-day exposure to cold temperature or feed deprivation at warm temperature on growth, physiological indices, and the expression of genes involved in muscle growth and metabolism. Juvenile channel catfish (initial mean weight 119.7 ± 8.0 g) were stocked into six 189 l tanks (20 fish per tank) with two replicate tanks for each of three treatments: Cold-fish reared at 10°C and fed to excess once daily, Feed-Restricted - fish reared at 27°C and deprived of food, and Control-fish reared at 27°C and fed to excess once daily. Muscle and blood samples were collected on days 1, 14, and 28, and final body weight, organ weight, and fillet fat and moisture were collected on day 28. Plasma samples were analyzed for cortisol and creatine-kinase activity. Abundance of mRNAs encoding myostatin, myosin heavy chain (MHC), and heat shock protein-70 (HSP-70) in muscle was determined via real-time quantitative PCR. Final body weight, weight gain, specific growth rate, condition factor, and liposomatic index were highest in control fish, intermediate in cold treatment fish, and lowest in feed-deprived fish. Fillet fat was lower and fillet moisture was higher for feed-restricted fish than for cold and control fish. Cold treatment fish had a greater hepatosomatic index than either control or feed-deprived fish. On day 1 cold treatment fish had greater plasma cortisol concentrations than control fish. Creatine kinase activity was greater for cold and feed-deprived fish than for control fish on day 14. Myostatin mRNA abundance was lower for cold and feed-deprived treatment fish than for control fish on day-1. Myostatin and HSP-70 mRNA was increased on day 14 and day 28 in the cold treatment fish relative to the control or feed-deprived fish. MHC mRNA was increased in the cold treatment fish on day 14. Voluntary suppression of feed intake associated with cold water temperature and feed restriction at warm temperature both reduced growth in channel catfish, but patterns of gene expression in the two treatments were not similar.