A total of 120 Tilapia nilotica fingerlings were fed diets supplemented with 0, 5000, 10 000 and 40 000 IU vitamin A k -' diet, respectively, at a rate of 3% of body weight for 18 weeks. The Vitamin A unsupplementef grou developed severe signs of vitamin deficiencies (restlessness, abnormal movement, blindness, exop%thalmia, haemorrhages of eyes, fins and skin, pot-belly syndrome, reduced mucous secretion). Growth and feed consumption were severely depressed, and the mortality rate amounted to 48%. An addition of 5000,lO 000 and 40 000 IU vitamin A resulted in a body weight gain of 23.9, 21.6 and 13.2 g, a feed consumption of 60.2, 59.6 and 50.2 g, a feed/gain ratio of 2.5, 2.8 and 3.8 /g and mortality rates of 7%, 7% and 33%, res ectively. Clinical signs and ost mortem lesions of ingerlings with hy ervitaminosis were impaireJ skeletal formation, especia8y i f the vertebrae, haemorrhages of the siin, necrosis of the caudal fin and enlargement of the liver and sfleen. 1t.k concluded that 5000 IU vitamin A kg-' diet covers the re uirement of Tilapia nilotica finger ings, while 10 000 IU already show signs of metabolic distortion an1 even higher dosages cause hypervitaminosis.

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