Interacting effects of dietary lipid level and temperature on growth, body composition and fatty acid profile of rohu, Labeo rohita (Hamilton)

Three isonitrogenous (320 g kg(-1) crude protein, casein and gelatine) semi-purified diets with 80 (L8), 130 (L13) and 180 (L18) g kg(-1) lipid (sunflower oil at increasing levels and cod liver oil fixed at 50 g kg(-1)) at three digestible energy levels (12 096, 13 986 and 15 876 kJ kg(-1) dry weight) and were tested, in triplicate, on rohu fingerlings (3.2 +/- 0.08 g) at two different temperatures (21 and 32 degreesC). Fish were fed to apparent satiation, twice daily, at 09.00 and 15.00 h, 7 days a week for 56 days. Maximum growth was obtained at a lipid level of 80 g kg(-1) (L8) at 21 degreesC (439.37%) and 130 g kg(-1) (L13) at 32 degreesC (481.8%). In general growth rate was higher at 32 degreesC than at 21 degreesC at all lipid levels. Tissue monounsaturated fatty acid (MUFA) contents decreased with increasing lipid level at 32 degreesC, but the reverse occurred at 21 degreesC. At 21 degreesC, Polyunsaturated fatty acid (PUFA) level increased significantly (P > 0.05) over initial values, but was affected insignificantly by dietary lipid level. At 32 degreesC, fish fed diet L13 had more n-3 fatty acid (FA) in liver and muscle than the other two dietary groups while at 21 degreesC, both liver and muscle FA profiles exhibited significant change (P > 0.05) in n-3 and n-6 FA content which corresponded to variation in percent addition of dietary lipid. However, n-3/n-6 ratio was higher for fish fed diet L13 at 32 degreesC and diet L8 at 21 degreesC and may be correlated with fish growth.