Effects of short-chain fructooligosaccharides on growth performance and hepatic intermediary metabolism in turbot (Scophthalmus maximus) reared at winter and summer temperatures

The effect of short-chain fructooligosaccharides (scFOS) incorporation on growth, feed utilization, body composition, plasmatic metabolites and selected liver enzyme activities of turbot juveniles reared at winter (15 degrees C) and summer (20 degrees C) temperatures was studied. Four comparable diets were formulated to contain circa 50:50 fish meal and plant ingredients as protein sources. Experimental diets included increasing levels of scFOS (0, 5, 10 and 20gkg(-1)). Final weight was higher at 20 degrees C, but thermal growth unit, feed efficiency, nitrogen and energy retention were better at 15 degrees C. scFOS supplementation did not affect fish growth performance. Fish reared at 15 degrees C had higher liver glycogen, visceral and hepatosomatic indices. Liver lipids, plasma triglycerides, total lipids, cholesterol HDL and LDL were higher in turbot reared at 20 degrees C. Malic enzyme, fatty acid synthetase, alanine aminotransferase and glutamate dehydrogenase activities were higher in fish reared at 15 degrees C. Malic enzyme was lower in turbot fed with 20gkg(-1) scFOS compared to control diet; however, fatty acid synthetase presented an increasing trend as dietary scFOS increased up to 10gkg(-1). Glutamate dehydrogenase activity was higher in fish fed the control diet. Results seem to indicate no benefits of scFOS incorporation to diets on growth performance of turbot.