Effects of a Trans-Galactooligosaccharide on Biochemical Blood Parameters and Intestine Morphometric Parameters of Common Carp (Cyprinus carpio L.)

Simple Summary Prebiotics are important feed additives used in aquaculture. These are substances that are breeding grounds for beneficial bacteria and that inhibit the development of pathogens; accelerate healing and regeneration of the intestinal epithelium; increase mucus production; help maintain normal pH in the intestine; limit the growth of pathogenic bacteria; increase calcium, iron and magnesium absorption; and also have beneficial effects on glucose and protein metabolism in the liver. The saccharide-based prebiotic used in the carp experiment had a positive effect on intestine morphometric parameters. Supplementation of this prebiotic had no negative effect on growth performance and did not disturb the homeostasis of the fish, as demonstrated by the values of biochemical blood parameters. Abstract The aim of the study was to evaluate the effects of a trans-galactooligosaccharide prebiotic (GOS) on the growth performance, biochemical blood parameters, and intestine morphometric parameters of common carp. The 60-day-long experiment was performed on one-year-old fish with a mean body weight of 180 g (+/- 5 g). Three diets were used: control diet 1 (C) with no microbiota affecting feed additives, diet 2 (B1) with 1% of prebiotic, and diet 3 (B2) with 2% of prebiotic, in four replications (tanks) per treatment and 25 fish per tank. At the end of the trial, 16 individuals from each group were used for analyses. The study showed that GOS supplementation did not affect growth performance. In turn, the prebiotic had a positive effect on the development of the intestine, and increased the height, width, and surface of the villi in B1 and B2 groups. The content of phosphorus (P) was significantly higher in B1 group compared with B2 group, which indicated that 1% addition of prebiotic causes better absorption of P from the intestine. The other biochemical indicators-namely lipid, protein and hepatic parameters, insulin, and Ca-were not affected by GOS treatment, which may indicate similar metabolic balance of fish in each experimental group. Serum triiodothyronine (TT3) and glucose (stress markers) concentrations were not significantly different among treatments groups. GOS may be recommended as a feed additive for common carp due to its positive effects on fish physiology and development of the gastrointestinal tract. However, our results suggest that 1% diet supplementation causes satisfactory reactions for the abovementioned aspects in comparison to control or 2% supplementation.