To determine the dietary protein and energy requirements of juvenile largemouth bass, 1350 feed-conditioned ®shes (average weight 14.46 0.81 g) were stocked in ninety 60-L cages, set up in 1000-L tanks at three cages/tank, and fed for 64 days with a dry, extruded feed containing six levels of crude protein (CP) (340±540 g kg ±1 , with increases of 40 g kg ±1 ) and ®ve levels of energy (150.7±171.7 kJ g ±1 feed, with increases of 5.2 kJ). The trial was set up in a 6´5 factorial, completely randomized design (n 3). Weight gain (WG), daily feed consumption (DFC), feed conversion rate (FCR), protein eciency ratio (PER), speci®c growth rate (SGR), protein and energy retention were recorded and evaluated. There was no interaction between feed energy and protein levels with all parameters evaluated. Data analysis by the broken line method showed that the minimum dietary requirement for maximum daily weight gain of 8.0 g kg ±1 is 435.9 g kg ±1 CP; the best feed conversion ratio (1.04:1) was attained with a minimum of 448.2 g kg ±1 CP; a minimum of 162.1 kJ g ±1 ; DFC was reduced as dietary protein and energy levels increased; dietary levels of 460±500 g kg ±1 CP led to best PER (1.665); best values for protein (33.14 g 100 g ±1 ) and energy (26.87 g 100 g ±1 ) retention were observed for ®sh feeding on the 420 g kg ±1 CP ration. Limits of energy to protein ratio to feed largemouth bass are 25.01 and 26.89 mg protein kJ ±1 , enabling feed conversion ratios of 0.96±1.10. KEY WORDS 1 640.6 g kg )1 crude protein;11.59 g 100 g )1 total lipids. 2 Units kg )1 of diet: Mn 40 mg; Fe100 mg; Zn 100 mg; Cu10 mg; Co 1 mg; I 1.5 mg; Se 0.45 mg; vitamin A 36 000 UI; pyridoxine 9 mg; vitamin D 3 4500 UI; vitamin E 150 UI; vitamin B 12 90 mcg; thiamin 6 mg; ribo£avin 18 mg; vitamin K 3 4.5 mg; folate 9 mg; biotin 0.6 mg; pantothenic acid 30 mg; niacin 90 mg; vitamin C 346 mg. 3
Five isonitrogenous diets formulated to contain 470 g kg−1 of crude protein, five different levels of crude lipids (190, 210, 230, 250 and 270 g kg−1), five different levels of carbohydrates (178, 155, 158, 125 and 110 g kg−1) and gross energy (21.2, 21.6, 22.4, 22.8 and 23.2 MJ kg−1) were used to investigate the effect of dietary lipid levels on performance and carcass composition of the surubim, Pseudoplatystoma coruscans (Agassiz). Triplicate groups of 11 fish with an average individual body weight of 5.1 ± 0.2 g were randomly assigned to 15 net cages and fed each test diet twice a day to apparent satiation for 64 days. At the end of the trial there were no significant differences in feed consumption or fish performance. No differences (P > 0.05) were observed in the lipid content of fish carcass and liver. On the contrary, visceral lipid increased (P < 0.05) with the increase in dietary lipid level. Protein and energy retention efficiencies were not significantly affected (P > 0.05) by the dietary lipid and carbohydrate levels. The results of this trial suggest that increasing dietary lipid levels from 190 to 270 g kg−1 did not improve growth performance or protein sparing and caused an undesirable increase in the visceral lipid content of surubim fingerlings.
Triplicate groups of juvenile suribim were fed for 183 days one of four different isonitrogenous (47.6% crude protein) and isolipidic (18.7% lipid) diets formulated using three different lipid sources: 100% fish oil (FO, diet 1); 100% pig lard (L, diet 2); 100% soybean oil (SO, diet 3), and FO/L/SO (1:1:1, w/w/w; diet 4). The tissue levels of fatty acids 18:2n-6 and 18:3n-3 decreased relative to corresponding dietary fatty acid values. The 20:5n-3 and 22:6n-3 composition of muscle and liver neutral lipids were linearly correlated with corresponding dietary fatty acid composition. In contrast, the 22:6n-3 composition of the brain and eye were similar among treatments. The 22:6n-3 level was enriched in all tissues, particularly in the neural tissues. Similar results were observed for tissue polar lipids: fatty acids content reflected dietary composition, with the exception of the 22:6n-3 level, which showed enrichment and no differences between groups. Given these results, the importance of the biochemical functions (transport and/or metabolism) of 22:6n-3 in the development of the neural system of surubim warrants further investigation.
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