D. Montero, M. Marrero, M.S. Izquierdo, L. Robaina, J.M. Vergara, L. Tort-1999
Aquaculture, 171 (3-4) : 269-278 (from Current Contents)
Abstract:
High stocking density is an aquaculture-related situation which causes crowding stress in fish and potentially affecting the immune system. Protection against disease can be induced through immunostimulation, enhancing defense mechanisms. Vitamins C and E are among the most important nutrients influencing the immune system, although the effect of these vitamins in the amelioration of stress in fish has not been studied in detail. An experiment was carried out to study the effect of dietary supplementation of vitamin C or vitamin E on the immune system of fish under a crowding stress situation in a commercial farm. A commercial diet for this species was supplemented with vitamin C or vitamin E and these diets were assayed at high stocking density (over 40 kg/m^3) and the results were compared with those from fish fed the commercial diet and held at farm conditions (20 kg/m^3). Some biological and immunological parameters were studied at the end of the experimental period. Fish held at high stocking density showed lower final weight than fish held at lower stocking density. These also showed higher plasma cortisol levels (over 6 ng cortisol/ml plasma for all the diets assayed) than those fish held at lower density (1.13 ng cortisol/ml plasma). High stocking density produced higher serum lysozyme activity values in fish fed the commercial diet compared with those fish held at lower density (67.49 and 36.84 units/ml, respectively). This effect was not observed in fish held at high stocking density but fed vitamin C and vitamin E supplemented diets (lysozyme activity: 21.97 and 19.71 units/ml, respectively). High stocking density also appeared to decrease serum alternative complement activity. In those fish fed the vitamin E supplemented diet, levels were similar to fish held at low stocking density, suggesting the role of this vitamin in this defense mechanism.
(Inst Canario Ciencia Marinas, POB 56, Las Palmas Gran Canaria 35200, Canary Islands, Spain, e-mail: dmontero@iccm.rcanaria.es)