Dietary vitamin E requirement of sunshine bass (Morone chrysops [] x M. saxatilis []) and apparent lack of interactions between vitamin E and selenium

Abstract

A 12-week feeding trial was conducted to determine the dietary vitamin E requirement of juvenile sunshine bass (Morone chrysops @ x M saxatilis d), and to investigate the possible interactions between dietary vitamin E and selenium. Sunshine bass initially averaging 1.8 ︢0.08 g (mean ︢s.d.) were fed semi-purified diets supplemented with 0. 2 mg S e/kg from Na2SeO3and either 0 (basal), 10, 20, 40, 60, or 80 mg vitamin E/kg as dl-(x-tocopheryl acetate. Fish fed the basal diet, which contained 5.8mg (x-tocopherol/kg dry weight, were darker in color and had reduced hematocrit values but did not exhibit reduced survival. Diets containing the lowest levels of vitamin E caused significantly (P<0.05) reduced weight gain and feed efficiency of fish compared to those fed diets supplemented with vitamin E at 20 to 80 mg/kg. Dietary supplementation of vitamin E caused incremental increases in the concentration of cc-tocopherol in both plasma and liver tissues. Regression analysis of weight gain data using the broken-line model indicated a dietary vitamin E requirement of 28 mg/kg dry diet. Two additional semi-purified diets containing either 0 or 60 mg vitamin E/kg without supplemental selenium also were included in the feeding trial and provided a 2 x 2 factorial arrangement to evaluate potential interactions between selenium and vitamin E. At the end of the 12week feeding trial, sunshine bass fed diets without supplemental vitamin E had significantly reduced weight gain and feed efficiency but selenium supplementation did not influence these responses. Dietary vitamin E and selenium also did not have significant effects on hematocrit of sunshine bass. Dietary vitamin E had a significant effect on plasma glutathione peroxidase (GSH-Px) activitv which was generally reduced at higher levels of vitamin E intake; however, dietary selenium had no significant effect on liver and plasma GSH-PX activity. Based on the results of this study, a dietary selenium deficiency was not induced and there were no interactions between dietary vitamin E and selenium in the nutrition of juvenile sunshine bass.