Approximate compositional values and tissue fatty acid profiles of Nile Tilapia (Oreachromis niloticus L.) fed azolla-diets in earthen ponds

The approximate general composition and the fatty acid profile of Nile tilapia fed Azolla-diets in ponds were studied for 90 days. Six isonitrogenous (29.2% CP) and isoenergetic (16.9 kJ·g−1) diets were formulated to contain 0% (A0), 10% (A10), 20% (A20), 30% (A30), 40% (A40) and 50% (A50) of Azolla meal (AM), as partial fish meal (FM) substitutes. Diet A0 without AM served as a control. Fish growth decreased as AM level exceeded 20% in diets (P < 0.05). Dry matter and crude protein showed no significant differences (P > 0.05). Crude lipid was significantly lower in fish fed A50 and significant differences were also found in crude ash (P < 0.05). Linolenic acid (LLA) decreased significantly when AM level in diets increased (P < 0.05). In contrast, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahex- aenoic acid (DHA) showed significantly higher values in fish fed high AM (P < 0.05). The n − 3/n − 6 ratio ranged from 0.35 to 0.49, with values being significantly higher in fish fed A20, A30 and A50. High level of the fern reduces growth without negatively affecting fatty acid in fish. Fish PUFA, especially the (n − 3) fatty acids, are affected posi- tively, even when fed 50% AM, which is good for the quality of the fish produced in regard to the benefits for the health of consumers.