Rtm. Baker et Sj. Davies, THE QUANTITATIVE REQUIREMENT FOR ALPHA-TOCOPHEROL BY JUVENILE AFRICANCATFISH, CLARIAS-GARIEPINUS BURCHELL, Animal Science, 65, 1997, pp. 135-142
Employing practical-type diets containing graded levels of all-rac-alp
ha-tocopheryl acetate (0, 5, 15, 30, 45, 60, 75 or 100 mg/kg), the qua
ntitative requirement for alpha-tocopherol by juvenile African catfish
(Clarias gariepinus Burchell) was investigated. Diets, defined with r
espect to selenium, fatty acid and ascorbate inclusion, were offered f
or 12 weeks during which catfish grew from 10 g to 120 g. Dietary regi
me had no significant effect on growth (P > 0.05), although haematocri
t values increased with increasing tocopherol dose above 25 mg/kg (ass
ayed) (R-2 = 0.71, P < 0.05). Tissue accretion of the vitamin increase
d concomitant with dietary dose (P < 0.001). Employing a colorimetric
assay for thiobarbituric acid reactive substances (TBARS) it was evide
nt that concentration of TBARS in muscle and liver reflected tissue ox
idation status, in that elevated dietary vitamin E resulted in decreas
ed assayed TBARS (P < 0.05). By broken-line analysis the requirement f
or this species to suppress lipid peroxidation was estimated as 30 to
40 mg all-rac-alpha-tocopheryl acetate per kg dry diet and this agrees
with published requirements of many fish species.