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Abstract. This study investigated the effect of partially replacing fish meal (FM) in diets with plant protein ingredients on the growth, feed intake, feed efficiency, and nutrient retention of Siberian sturgeon, Acipenser baerii Brandt, juveniles. FM was replaced with soy protein concentrate (SP) and rape meal (RM). Three experimental feeds (40% crude protein, 10% fat) were prepared by extrusion. The protein sources in diet FM were fish meal, blood meal, and fish hydrolysate. In diet SP, the fish meal and fish hydrolysate were substituted with soy protein concentrate, and in diet SP-RM, with soy protein concentrate and rape meal. Each diet was fed to triplicate groups of sturgeon with a mean initial mass of 14 ± 1.3 g. The growth test lasted for 50 days, and were carried out in flow-through tanks of 600 dm 3 capacity. The sturgeon from group FM reached an individual body weight that was about 10% higher than that of the fish from the other dietary variants; the significance of the differences was confirmed statistically (P < 0.05). The specific growth rates (SGR) were similar during the growth test (about 4% d -1) and did not differ significantly. The feed conversion (FCR) and protein efficiency (PER) ratios were not significantly affected by the different dietary treatments, and were about 1.2 and 2.1, respectively. The proximate composition of the sturgeon bodies was similar, except with regard to lipid content. Protein retention, which ranged from 29.5 to 33.2%, was higher in groups SP and SP-RM. Lipid retention was the lowest in the SP-RM group. The results indicated that soy protein concentrate and rape meal are sufficient partial fish meal substitutes in feed for sturgeon juveniles.

SynopsisThe developmental interval, body length, dry and wet weight were determined in carp larvae during the first 2 weeks of exogenous feeding. Six feeding groups were reared at 26OC; four groups received different artificial diets, whereas zooplankton-fed larvae and unfed larvae served as controls. It was found that larval developmental rate can be modified by the type of food. The diet affects the relationship between developmental step and weight. The effect of diet on the relationship between development and length becomes manifest at older steps (after longer feeding the same diet). A threshold point, after which satisfactory results of feeding artificial diets to carp larvae can be expected, depends not only on body size but also on the degree of development.

The aim of the study was to determine the possibility of inclusion of cold‐pressed rapeseed cake (CPRC) in diets for common carp, Cyprinus carpio L. Four isonitrogenous (322 g kg−1 crude protein) and isoenergetic diets (17.5 MJ kg−1) with four levels of CPRC incorporation 0, 110, 220 and 330 g kg−1 (treatments RC0, RC11, RC22 and RC33, respectively) were evaluated in a 50‐day growth test with common carp of 500 g initial weight. Statistically significant higher final weights (1215–1243 g) were obtained in fish fed diets including CPRC. Fish growth rates were nearly identical in all treatments (specific growth rate of 1.7–1.8% day−1). Similar results were obtained in respect of feeding coefficients (FCR) that ranged from 1.6 to 1.8. Crude protein and ash concentration in fish bodies did not change. Statistically significant decreases in moisture content were found in carp in groups RC22 and RC33. Statistically significant increase of crude lipid in fish bodies were found in groups RC22 and RC33. The slaughter traits and meat quality analysis of carp did not show significant differences. We conclude that it is possible to include up to 330 g kg−1 of CPRC in diets of 2‐year‐old common carp without significant effects on growth and food utilization.

Four isonitrogenous (gross protein content 32%) and isoenergetic (gross energy content 4 080 kcal/kg) diets were prepared by extrusion to investigate the effects of different cereal grains (barley -diet A, wheat -diet B, triticale -diet C, rye -diet D) as carbohydrate compounds of extruded feeds for carp. The physical and chemical properties of the feeds were established. A 60-day growth test was performed in experimental ponds of 40m 2 area. Each diet was fed to three groups of fish (initial average weight 200 ± 10 g). The following rearing effectiveness indices were used in the final evaluation of the growth test: weight gain (WG, %), specific growth rate (SGR, %/d), food conversion ratio (FCR), protein efficiency ratio (PER) and protein retention (PR, %). Conclusions were based on statistical analysis using the Statistica 5.0 package. The results obtained in the growth test did not show any differences in the evaluated feeds regarding their usefulness in the nutrition of carp (there were no statistically significant differences in the values of fish rearing parameters, P ≤ 0.05). The recorded growth parameters of carp were as follows: WG: 308.48-324.0%; SGR: 2.81-2.92%/d; the feed conversion coefficients were: FCR: 1.43-1.50; PER: 1.75-1.83; PR: 29.54-31.72%. Keywords: common carp; feeding; feeds; extrusion; carbohydrate components 308Original Paper Czech J. Anim. Sci., 49, 2004 (7): 307-314 MATERIAL AND METHODSFormulations of experimental diets were calculated using a computer program wri�en by the linear Simplex Method in Turbo Pascal 5.0. Different kinds of cereal grains as main carbohydrate components were used in the feeds: in feed A -barley, in feed B -wheat, in feed C -triticale and in feed D -rye (Table 1).Feeds were produced by the barothermal method in a single-start worm extruder, type N-60, manufactured by Metalchem Gliwice, Poland. Feeds were conditioned by adding hot water and steam to the mixer to reach 65-70°C and 9-11% moisture level and then they were extruded under the following technological parameters: -moisture of feed 10% -cylinder temperature in the zone of increasing pressure 81°C-cylinder temperature in the zone of high pressure 93°C -head temperature 105°C -worm revolutions 63 rev/min -time of passage through the extruder 78 s -nozzle diameter 6.0 mm The extrudate leaving the extruder was cut with rotary knife into 8 mm pellets, they were spread on sieves, let cool down and then dried in a stream of heated air. A�er drying, the diameter of pellets was 6.6-6.9 mm. The granules were covered with rapeseed oil (2.0% of the granule weight) heated to 70°C by spraying in a pelletising drum.Water stability of experimental feeds was determined by Hastings-Hepher method (Hepher, 1968) modified by Szumiec and Stanny (1975). It was done in a water bath, on the basis of feed weight loss a�er the bath treatment and subsequent drying to a constant temperature 105°C. Another criterion of water 309Czech J. Anim. Sci., 49, 2004 (7): 307-314 Original Paper stability assessment was the ox...