Effects of vitamin E on growth, liver vitamin E and serum cortisol level in juvenile soft-shelled turtles (Pelodiscus sinensis)
ZHOU Xian-Qing ①② NIU Cui-Juan① SUN Ru-Yong ①** (① College of Life sciences, Beijing Normal University, Beijing 100875, China) (② Department of Laboratory Animal Science, Capital University of Medical Sciences, Beijing 100054, China)
To investigate the effects of vitamin E on growth, liver vitamin E and the serum cortisol level of juvenile soft-shelled turtles, we estimated the growth in juvenile soft-shelled turtles by specific growth rate, analyzed liver vitamin E with a high pressure liquid chromatogram (HPLC) and determined serum cortisol content using the radiate immune method. Growth in juvenile soft-shelled turtles was depressed in two groups that received vitamin E supplementation at 1 000 and 5 000 mg/kg of diet. Levels of liver vitamin E in turtles that received vitamin E supplementation at 500, 1 000 and 5 000 mg/kg of diet were significantly higher than in the control group. The level of liver vitamin E increased exponentially with increasing dietary vitamin E within the range 0-1 000 mg/kg of diet, reaching saturation when dietary vitamin E reached 5 000 mg/kg of diet. The mean serum cortisol content in two groups that received vitamin E supplementation at 0 and 50 mg/kg of diet was significantly higher than that in four groups supplemented at 250, 500, 1 000 and 5 000 mg/kg of diet. These results suggest that high doses of vitamin E reduce growth rates and serum cortisol levels in juvenile soft-shelled turtles, and that liver vitamin E increases with increasing dietary vitamin E within certain limits[Acta Zoologica Sinica 49(1):40-44,2003].