Effect of lipid level in a compound diet on the development of red drum (Sciaenops ocellatus) larvae

Red drum larvae were fed, from day 11 to day 24 post-hatch, with Artemia (LP group) or two isoproteinic-formulated diets with varying lipid levels, 15% (L15 group) and 30% (L30 group). The lipid fraction was composed of a mixture of cod liver oil and soy lecithin. Larvae fed Artemia exhibited the greatest length; L30 diet induced a larvae length significantly greater than that obtained with L15 diet (P<0.05). No difference was observed in larvae survival among the three dietary groups. The increase in dietary lipid concentration led to an increase in amylase and trypsin secretion levels in 24-day-old larvae. The pancreatic secretion level measured in L30 group was close to that of LP group, suggesting that the maturation of the pancreatic functions was normally developed. Red drum larvae fed the diet containing the higher lipid content (L30) exhibited a more developed brush border membrane digestion in the intestine than larvae fed L15 diet (P<0.05). Phospholipase A2 was stimulated by the increase of phospholipids in the diet, but no difference was observed for lipase between the two compound diet-fed groups; the LP group exhibited the lowest lipase activity. A plateau in lipase activity may have occurred in red drum larvae from 15% fat level in the diet, suggesting that the maximal lipase activity was reached with 12% neutral lipid in the diet. The positive effects observed with high dietary fat may be due to the phospholipid fraction of the lipid mixture used.