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

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 approximate to 10 degrees C and fed to excess once daily, Feed-Restricted-fish reared at approximate to 27 degrees C and deprived of food, and Control-fish reared at approximate to 27 degrees 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 protem-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. (c) 2005 Published by Elsevier B.V.