Effects of a Trans-Galactooligosaccharide on Minerals Content of Common Carp (Cyprinus carpio L.) Tissues

Common carp (Cyprinus carpio L.) is a dominant fish species in aquaculture, and as it is a stomachless species, absorption and digestion of nutrients take place in the intestine. The aim of the study was to evaluate the effects of a prebiotic on the content of selected minerals found in the meat, gills, and skeleton of common carp. The research applied trans-galactooligosaccharide (GOS) prebiotic produced by enzymatic transgalactosylation of milk lactose by whole cells of Bifidobacterium bifidum. The following diets have been applied: control diet without feed additives (C), diet 2 (B1) with 1% of GOS, and diet 3 (B2) with 2% of GOS. In the freeze-dried samples, concentrations of the analyzed metals were determined using atomic absorption spectroscopy (AAS). The content of phosphorus was determined using colorimetric method. The analyses confirmed that the highest level of Mg was detected in the skeleton of fish fed with 1% GOS (2.51 g kg^-1) and was significantly higher compared the control treatment (2.11 g kg^-1) (P < 0.05). Zn content in fish meat fed with 1% GOS (35.41 mg kg^-1) was significantly higher (P < 0.05) than in the control group (24.59 mg kg^-1). The tissue that accumulated the greatest amount of Zn was the gills. GOS had a positive effect on Fe accumulation in the meat, gills, and skeleton. It has been concluded that supplementation of feed with 2% GOS significantly influenced the positive correlations between Mg and P in the meat and skeleton, Fe-Ca correlation in gills, and Fe-Zn correlation in the skeleton.