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The amounts of energy channeled into growth (P), maintenance (R), excretion (U) and exuviae (E,) were quantified in six dietary treatments during early postlarval development in Litopenaeus setiferus and Litopenaeus vannamei reared at 28 +/- 1 degreesC and 35 +/- 1% salinity. The six diet combinations were: (1) freshly hatched Artemia nauplii, (2) freshly hatched Artemia nauplii supplemented with algae, (3) microparticulate commercial diet (MCD), (4) MCD supplemented with algae, (5) Artemia nauplii partially substituted (50%) by MCD and (6) Artemia nauplii partially substituted (50%) by MCD supplemented with algae. Oxygen consumption, ammonia excretion and dry weight were measured from postlarvae day I (PL1) to PL10 (I to 10 days after metamorphosis). Energy distribution in both species was affected by diet with significantly higher proportion of energy allocated into production (1.49 J day(-1) for L. setiferus and 1.77 J day(-1) for L. vannamei) when animals were fed a mixed diet. The proportion of assimilated energy channeled into production (P/As) was greater when both species were fed mixed diet and was lower when fed on MCD alone or MCD plus algae. On the contrary, the proportion of assimilated energy used in respiration (R/A) was higher for both species when fed on MCD alone or MCD plus algae, with the lowest values in animals fed on the mixed diet. Low values of net growth efficiency (K-2) were found in both species when the main food was MCD (alone or supplemented with algae), with the highest K-2 when animals were fed the mixed diet. Results show that divergences between these two species during early postlarval stages only appear when animals were in a poor physiological condition due to an inefficient diet. Artemia nauplii, partially substituted by MCD with a supplement of algae, integrated a high-quality diet for both species producing high net growth efficiency. (C) 2004 Elsevier B.V. All rights reserved. |
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