W.-B. Liu

Protein-sparing effect of dietary lipid in practical diets for blunt snout bream (Megalobrama amblycephala) fingerlings: effects on digestive and metabolic responses

This study aimed to evaluate the protein-sparing effect of dietary lipid on digestive and metabolic responses of fingerling Megalobrama amblycephala. Fish were fed nine practical diets with three protein levels (270, 310 and 350xa0gxa0kg−1) and three lipid levels (40, 70 and 100xa0gxa0kg−1) for 8xa0weeks. Weight gain was significantly affected only by dietary lipid levels with the highest found in fish fed 70xa0gxa0kg−1 lipid. Relative feed intake and whole-body protein content showed little difference among all the treatments. Activities of intestine lipase and amylase increased significantly as dietary lipid levels increased, whereas little difference was observed in protease activities. Liver lipid content was significantly affected only by protein levels with the lowest found in fish fed 310xa0gxa0kg−1 protein. Liver aspartate aminotransferase (GOT) activities increased significantly with decreasing lipid levels, whereas the highest GOT activity was obtained in fish fed 310xa0gxa0kg−1 protein in terms of dietary protein levels. Activities of liver lipoprotein lipase, total lipase and plasma cholesterol concentration of fish fed 350xa0gxa0kg−1 protein were significantly lower than that of the other groups, whereas the same was true for plasma 3, 5, 3′-triiodothyronine level of fish fed 270xa0gxa0kg−1 protein. The results indicated that an increase of dietary lipid content from 40 to 70xa0gxa0kg−1 can enhance the growth and digestive enzyme activities of this species and reduce the proportion of dietary protein catabolized for energy without inducing hepatic steatosis; meanwhile, decreasing protein level from 350 to 310xa0gxa0kg−1 leads to the increase of lipase activities both in intestine and liver coupled with the reduced liver lipid content.

Effect of trichlorfon on oxidative stress and hepatocyte apoptosis of Carassius auratus gibelio in vivo

To investigate the effect of trichlorfon on oxidative stress and hepatocyte apoptosis of Carassius auratus gibelio in vivo, the fish were exposed to 0, 0.5, 1.0, 2.0 and 4.0xa0mgxa0l−1 trichlorfon concentrations for 30xa0days. At the end of the experiment, plasm antioxidant activities, hepatic total nitric oxide synthase (T-NOS) activity, xanthine oxidase (XOD) activity and hepatocyte apoptosis rate were analyzed. The results showed hepatic T-NOS activities, XOD activities and hepatocyte apoptosis rate were increased with trichlorfon concentration increase. The hepatic MDA content was increased significantly at 4.0xa0mgxa0l−1 trichlorfon treatment. The disturbance of antioxidative balance was observed based on the monitoring of the plasm superoxide dismutase (SOD), catalase (CAT) activities and vitamin E levels. The current study revealed that trichlorfon influenced fish plasma antioxidative status, caused lipid peroxidation (LPO) then resulted in hepatocytes apoptosis.