LAUSR

Abstract The effects of guar gum, when used as a feed binder, on growth performance, digestive enzyme activity, and intestinal histology in gibel carp were evaluated. Four isonitrogenous and isoenergetic diets were formulated and supplemented with 0%, 1%, 3%, and 5% guar gum. The different diets were fed to triplicate groups of gibel carp (mean initial weight: 5.60 ± 0.003 g) for 51 d. Feed supplemented with 1% guar gum had no effect on specific growth rate, feed efficiency, condition factor, or protein retention efficiency as compared to the control group; this level of supplementation increased microvillus length in the distal intestine and increased fecal viscosity. In contrast, 5% guar gum supplementation increased feed hardness, decreased feed water solubility, and decreased total nitrogen content in the soaking water after 3-h immersion. However, 5% guar gum supplementation decreased feed intake and induced distal intestine damage, as indicated by shorter microvilli as compared to the control group. Supplementation with 5% guar gum also decreased the activity levels of intestinal digestive enzymes (chymotrypsin, amylase, and alkaline phosphatase) and decreased plasma total cholesterol and triglycerides, and finally reduced fish growth. Dietary supplementation with 1% guar gum increased fecal viscosity sufficiently to decrease water pollution, without significant adverse effects on growth performance, feed utilization, and intestinal microstructure in the gibel carp.