REDUCTION OF STRESS-RESPONSE IN CARP, CYPRINUS-CARPIO L., HELD UNDER DETERIORATING ENVIRONMENTAL-CONDITIONS, BY ORAL-ADMINISTRATION OF BOVINE LACTOFERRIN

Bovine lactoferrin (LF) was evaluated for its ability to suppress stre ss reactions in carp, Cyprinus carpio L., held under deteriorating env ironmental conditions. Three test diets containing different levels of LF (0.01, 0.1 and 1%) were fed at 2% of fish body weight per day, i.e . LF at 2, 20 and 200 mg kg(-1) body weight day(-1) was administered o rally to carp for 14 days at 20 degrees C. In the fish reared at a den sity of 2 individuals 10 l(-1), plasma cortisol, adrenaline and noradr enaline decreased in the groups fed with 0.1 and 1% LF content diets. In the fish held at a density of 10 individuals 10 l(-1) for 3 days, p lasma cortisol, adrenaline, noradrenaline, dopamine and glucose were h igher than those at 2 individuals 10 l(-1) in both the control and LF- treated groups. The extent to which these parameters were elevated in the fish held at the same density was reduced with increasing LF conte nt of the diet. Twenty-four hours after exposure to hypoxic conditions (dissolved oxygen level, 2.5 mg l(-1)), haemoglobin, haematocrit, pla sma cortisol, adrenaline, noradrenaline and dopamine increased signifi cantly in all groups. The responses of hypoxic fish fed with 0.1 and 1 % LF diets for 14 days were smaller than those of the controls. These results suggest that LF has an ability to reduce the stress response o f carp held under deteriorating environmental conditions.