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Diets with graded levels of the experimental microbial phytase SP1002 (0, 500, 1000, 2000 and 4000 FTU/kg) were fed to juvenile Nile tilapia (average BW = 68.8 g) for 60 days (n = 4). A digestibility trial ran parallel to the growth trial using 0.3 g TiO2/100 g as an indigestible marker. The efficiency of phytase supplementation was evaluated by parameters of growth response, crude protein and mineral utilization (using body composition data), apparent nutrient digestibility, mineral content in scale and vertebra and inorganic phosphorus in blood plasma. Data were submitted to ANOVA and Tukey-test using SAS-program. Significant improvements (p < 0.01) were found for growth, FCR and SGR, mainly for diets with 1000 and 2000 FTU/kg phytase supplementation. Protein utilization was significantly increased and maximized between 1000 and 2000 FTU/kg. Phosphorus utilization increased significantly up to 4000 FTU/kg. Digestibility of protein and phosphorus was also significantly improved. Phosphorus concentration in the blood, vertebra and scale increased significantly after phytase addition. Similarly, calcium and magnesium concentration in vertebra and scale were increased. Generally, phytase supplementation between 1000 and 2000 FTU/kg resulted in growth rates and mineralization parameters similar to a control diet with inorganic phosphorus.

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.

Simple SummaryWorld communities are concerned about the increasing impact of the aquaculture activities on fisheries resources. Aquaculture sector uses 2–5 times more fishmeal to feed farmed species than what is supplied by the farmed product. Therefore, the reduction of fishmeal dependency may provide more economic and environmentally friendly aquaculture. By identifying alternative protein sources, the authors find that brewer’s yeast is a suitable raw material as fishmeal replacement in feed of tilapia. The 15% inclusion may promote growth without affecting the end-product quality. AbstractA 51-day feeding trial was carried out to determine the effects of various dietary levels of brewer’s yeast, Saccharomyces cerevisiae, in the growth performance, body composition and nutrient utilization in Nile tilapia, Oreochromis niloticus, juveniles. Fish (7.6 ± 0.3 g) were stocked into eighteen 1,000-L tanks (100 fish per tank; n = 3) and fed to apparent satiation six isonitrogenous (27% crude protein) and isoenergetic (19 kJ/g) diets, formulated to contain different dried yeast levels (0%, 10%, 15%, 20%, 30% or 40% diet) in substitution to fishmeal. Body weight tripled at the end of the feeding trial for fish fed up to 20% dietary yeast incorporation. Daily growth coefficient (DGC, % body weight/day) decreased with increasing dietary yeast level (P < 0.0001). Voluntary feed intake (VFI, %BW/day) did not vary significantly with increasing yeast level. Fish fed 40% yeast showed significant reduction in protein efficiency rate, protein retention and nitrogen gain. Increasing levels of dietary yeast did not significantly affect protein or lipid digestibility. Dietary dried yeast was seemingly palatable to tilapia juveniles and was suitable up to 15% inclusion to promote growth and efficient diet utilization, without affecting body composition.