Two experiments were carried out in order to evaluate the essentiality of phospholipid (PL) addition to semi-purified diets for first-feeding carp larvae. In Experiment I (25 days), a casein-based diet was supplemented with 0, 2 or 4% of a purified PL source (PL level in source: 98%) and with 0 or 4% of peanut oil (PO). One casein-based diet without PL was supplemented with choline chloride. In Experiment II (21 days), the same casein-based diet was supplemented with 7 commercial or experimental PL sources (PL content in sources: 55-81%). Sources included soybean PL, lyse soybean PL, obtained by treatment with phospholipase A(2), and soybean PL with Ca2+ added in order to decrease the oil/water (O/W) emulsifying properties. Diets were made isolipidic by adding PO. One diet was formulated to be PL-free. In both experiments, all semi-purified diets supplemented with PL significantly improved survival and growth of carp larvae in comparison with PL-deficient diets. Results indicate that the beneficial effect of PL was not due to the correction of a choline deficiency or to the correction of an essential fatty acid deficiency and thus supported the idea of the essentiality of the PL entity for the early nutrition of larvae. The effect of PL seemed unrelated to their emulsifying properties as larval performances were not affected by Ca2+ enrichment while they were decreased by lyso-PL supplementation. It is presumed that the PL requirement for membrane building and renewal could be especially high during the fast growing larval stages and could exceed the endogenous ability of PL synthesis. Attention should be paid to an adequate dietary PL supply when larvae are offered artificial diets instead of PL-rich live food.
