The present study investigated the effect of varying dietary protein-to-lipid ratios (P/L) on growth performance and body composition of pike perch (Sander lucioperca) fingerlings with an initial body weight of 1.35-1.40 g. Triplicate groups were reared during 56 days in recirculation systems and fed six experimental diets containing three dietary levels of lipid (90, 130, 170 g kg )1 of dry matter, d.m.) combined with two levels of dietary protein (470, 540 g kg )1 d.m.). During the experimental period the fixed feeding rates decreased from 10% to 5% of the total fish biomass per day. In contrast to previous results obtained with this species, the present study clearly demonstrated the occurrence of protein sparing effect. The best results for feed conversation ratio and specific growth rates were obtained in the treatments containing highest lipid level: diet 3 (P/L 47/17) and diet 6 (P/L 53/17). The d.m. and crude lipid contents of pike perch whole body increased in direct proportion of the dietary lipid levels. No difference was observed on crude protein and ash content among the treatments. Increasing hepatosomatic index at highest dietary lipid level suggested a limited lipid utilization of percids. KEY WORDS

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To evaluate isolated pea protein as feed ingredient for tilapia (Oreochromis niloticus) juveniles, triplicate groups were fed with four isonitrogenous [crude protein: 421.1^427.5 g kg À1 in dry matter (d.m.)] and isoenergetic (gross energy: 20.46^21.06 MJ kg À1 d.m.) diets with varying protein sources for 8 weeks. Fish meal-based protein content of diets was substituted with 0% (diet 100/0 5 control group), 30% (diet 70/ 30), 45% (diet 55/45) and 60% (diet 40/60) isolated pea protein. Tilapia juveniles with an initial body weight of 2.23^2.27 g were fed in average at a level of 5% of their body weight per day. Highest individual weight gain (WG: 21.39 g) and speci¢c growth rate (SGR: 4.21% day À1 ) and best feed conversion ratio (FCR: 0.90) were observed in tilapia fed diet 100/0, followed by ¢sh-fed diet 70/30 (WG: 19.09 g; SGR: 4.03% day À1 ; FCR: 0.98), diet 55/45 (WG: 16.69 g; SGR: 3.80% day À1 ; FCR: 1.06) and diet 40/60 (WG: 16.18 g; SGR: 3.74% day À1 ; FCR: 1.06). Although ¢sh fed diet 100/0 showed the best performance, inclusion of 30% protein derived from pea protein isolate resulted in a growth performance (in terms of WG and SGR) that did not di¡er signi-¢cantly from diet 100/0 in contrast to ¢sh fed diet 55/45 and 40/60. Crude ash content in the ¢nal body composition of the experimental ¢sh decreased with increasing dietary pea protein content, while crude protein and lipid content remained equal between the groups. Signi¢cant decreasing growth performance and body ash incorporation of tilapia at higher inclusion levels seem to be mainly related to the dietary amino acid pro¢le and phytic acid contents. Ã Total sulphur-containing amnio acid (methionine1cystine) requirement is 3.21g16 g À1 dietary N.wTotal aromatic amino acid (phenylalanine1tyrosine) requirement is 5.54 g16 g À1 dietary N.Tilapia fed pea protein isolate C Schulz et al.

A 56-day feeding trial was conducted to access the effect of housefly maggot meal (magmeal) diets on the performance, concentration of plasma glucose, cortisol and blood characteristics of Oreochromis niloticus fingerlings. Seven feeds formulated to contain 36% protein and 20 kJ g(-1) gross energy (dry matter basis), were prepared by replacing fish meal with magmeal. Fifteen fingerlings (initial average weight 2.0 +/- 0.1 g) stocked per experimental tank were fed in triplicates at 5% body weight in two portions per day (a level previously established). Growth and food conversion ratio were adequate and comparable without any significant differences (p < 0.5) between feeding groups. Mean values for haematocrit and plasma glucose were not significantly different (p < 0.05) among the feeding groups. Fish group fed control diet (containing highest inclusion level of fish meal and without magmeal) gave the lowest haemoglobin concentration (5.96 +/- 0.22 g dl(-1)). This value was significantly different from other feeding groups. Stressful conditions in fish and in mammals are associated with decreased growth, haematocrit (packed cell volume) and haemoglobin values, increased whole blood glucose (hyperglycaemia) and plasma cortisol concentrations. No such physiological changes were observed in this study. Results suggest that feeding O. niloticus fingerling with magmeal diets did not cause any form of physiological stress. Magmeal can be used as a good alternative protein source in tilapia diets.