low vitamin e in diet reduces stress
resistAnce of gilthead seabream (sparus aurata) juveniles
D. Montero, L. Tort, L. Robaina, J.M. Vergara, M.S.
Izquierdo-2001
Fish & Shellfish Immunology, 11(6) : 473-490
Abstract:
This study investigates the effect of
dietary vitamin E on juveniles of gilthead seabream under stressful
situations, focusing on the effects on growth, haematology,
some immune parameters and plasma cortisol as
indicators of stress. Two sardine meal-based experimental
diets, one of them supplemented with 150mg of alpha
tocopherol kg-1of diet (control) and another one without
vitamin E supplementation (diet NE), were assayed
under two different stress conditions: overcrowding as
a chronic stressor (during 15 weeks) and repetitive
chasing as an acute repetitive stressor.
Low levels of vitamin E in the diet
depleted alternative complement pathway activity [from 167·23U
ml-1(control fish) down to 100·99U
ml-1] and also non-specific haemagglutination.
Also, fish fed a non-supplemented diet showed an
elevation of plasma cortisol basal levels without a
stressor influence [from 3.91ng cortisol ml-1plasma
(control fish) up to 21.70ng cortisol ml-1plasma]. Low
levels of vitamin E in the diet also produced an
increase of erythrocyte fragility.
Under chronic stress, fish fed the vitamin
E-deficient diet showed a reduction in growth and survival,
and alterations in haematological parameters, such
as an additional haemoconcentration in response to overcrowding
when compared with control fish. Under repetitive
stress, fish fed the vitamin E deficient diet showed
faster elevation of plasma cortisol levels in response
to stress and a lower survival rate than control fish.
Production of oxygen radicals by blood neutrophils was
reduced under repetitive stress in fish fed the
non-supplemented diet. These results suggest that fish
fed the vitamin E-deficient diet had lower stress
resistance.
(Instituto
Canario de Ciencias Marinas, Gobierno de Canarias, P.O. Box 56, 35200 Telde,
Las Palmas, Canary Islands, Spain)