Effects of dietary organic chromium on gilthead seabream (Sparus aurata L.) performances and liver microsomal metabolism

The effect of yeast and chromium yeast on gilthead seabream (Sparus auratus L) performance, carcass indices and body composition was studied. Whether supplementation affected liver microsomal mixed function oxidases using either multibioprobes (testosterone) or highly specific substrates to cytochrome P450 (CYP) isoforms was also investigated. Seabream juveniles (35-37 g initial weight) were allocated into 12 800 L tanks of 50 fish each for 8 7 days and fed pelleted experimental diets, i.e. control, yeast supplemented (1.6%) and chromium yeast supplemented at both low (800 p.p.b.) and high chromium level (53 810 p.p.b.). At the end of the experiment, growth, feed conversion ratio, thermal-unit growth coefficient, carcass yield, hepatosomatic index, and carcass and fillet proximate compositions were similar among treatments and only condition factor was statistically different. Organic chromium at both doses affected CYP-catalysed drug reactions slightly, as shown by the modest effect on the regio- and stereoselective hydroxylations of testosterone, as well as the metabolism of the selected probes. Overall, we found that chromium yeast did not change performance substantially, nor carcass indices, carcass and fillet chemical compositions, or hepatic xenobiotic metabolizing enzymes of gilthead seabream. © 2001 Blackwell Science Ltd.