The protective effect of dietary extract of Astragalus membranaceus on the high stocking density, copper and trichlorfon in Jian carp (Cyprinus carpio var. Jian)

Abstract

This study was designed to examine the protective effects of extract of Astragalus membranaceus (EAM) against stress, which induced by high stocking density, Cu and trichlorfon exposure in Jian carp (Cyprinus carpio var. Jian). The husbandry period (23.0 ± 1 °C) for high stocking density (0.97 fish/L) was 60 days with the initial fish weight 7.2 ± 0.2 g, and Cu (0.7 mg/L) and trichlorfon (2.2 mg/L) exposure was 4 days after feeding trial (30 days) with the initial fish weight 10.5 ± 0.3 g. Stress of high stocking density and Cu exposure decrease 48.2 % of fish weight gain and reduced 97.6 % of feed intake. Meanwhile, trichlorfon exposure induced 100 % fish rollover. High stocking densities and Cu exposure decreased activities of amylase, trypsin, as well as Na+/K+-ATPase and alkaline phosphatase and increased malonaldehyde content in fish digestive organs (P < 0.05), indicating an interruption of digestive ability and antioxidant status. Furthermore, trichlorfon exposure decreased activities of lactate dehydrogenase, superoxide dismutase, catalase, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase in fish muscles (P < 0.05), indicating an interruption on bioenergetic homeostasis and antioxidant status. Dietary EAM supplementation relieved these detrimental effect, which induced by high stocking density, Cu and trichlorfon exposure. The optimum dietary EAM supplementation were 5.23, 4.79 and 5.12 g kg/diet for Jian carp under high stocking densities, Cu and trichlorfon exposure, respectively. Our study indicates that dietary EAM supplementation offers a feasible way for relieving the stress which induced by inappropriate high stocking densities, Cu, as well as trichlorfon.