Effects of dietary starch on biochemical indexes of the serum of cobia (Rachycentron canadum)

To investigate effects of re-feeding following fasting on plasma glucose, total protein, triacylglycerol, total cholesterol, low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein-cholesterol (HDL-C) contents in cobia fasted for 24h, six diets were formulated to contain 0% (control), 6%, 12%, 18%, 24% and 30% starch, respectively. The results showed that the serum glucose levels of cobia after re-feeding with each diet elevated from 0h to 5h and then started to decline till 7h that the glucose levels were similar to those at 0h. Different dietary starch and postprandial time did not significantly influence the total protein levels in serum. The triacylglycerol levels in serum elevated from 0h to 5h and then began to decline. At 7h, the levels were similar to those at 0h. In the control group, the concentration of cholesterol in serum increased from 0h to 2h and then decreased from 2h to 7h that reached to fasting level. In other groups, the serum cholesterol levels increased from 0h to 5h and then began to decline; then, it also reached to fasting level at 7h. The levels of LDL-C increased from 0h to 5h and then began to decline. At 7h, the levels of LDL-C declined to the basal level. However, different dietary starch and postprandial time did not significantly influence the levels of LDL-C in serum. In the group of 24%, the levels of HDL-C at 5h were significantly higher than those at 0 and 24h. No significant differences were found for the levels of HDL-C among other groups. In conclusion, the glucose levels increased and then declined. The peak glucose levels increased with the increase of dietary starch level up to 12% and remained nearly the same thereafter. The levels of triacylglycerol and cholesterol in serum increased after re-feeding, but there were no significant differences in the LDL-C and HDL-C levels in serum after re-feeding