Triplicate groups of gibel carp Carassius auratus gibelio (initial body weight: 5.25 ± 0.02 g) were fed for 8 weeks at 20-25°C on five isonitrogenous (crude protein: 400 g kg )1 ) and isoenergetic diets (gross energy: 17 kJ g)1). Meat and bone meal (MBM) or poultry by-product meal (PBM) were used to replace fish meal at different levels of protein. The control diet contained fish meal as the sole protein source. In the other four diets, 150 or 500 g kg )1 of fish meal protein was substituted by MBM (MBM 15 , MBM 50 ) or PBM (PBM 15 , PBM 50 ). The results showed that feeding rate for the MBM 50 group was significantly higher than for other groups except the PBM 50 group (P < 0.05). Growth rate in the MBM 15 group was significantly higher than that in the control (P < 0.05), while there was no significant difference in growth between the control and other groups (P > 0.05). Feed efficiency and protein efficiency ratio in MBM 50 was significantly lower while that in MBM 15 was significantly higher (P < 0.05). Replacement of fish meal by MBM at 500 g kg )1 protein significantly decreased apparent dry matter digestibility (ADC D ) and gross energy (ADC E ) while apparent protein digestibility (ADC P ) was significantly decreased by the replacement of MBM or PBM (P < 0.05). The results suggest that MBM and PBM could replace up to 500 g kg )1 of fish meal protein in diets for gibel carp without negative effects on growth while 150 g kg )1 replacement by MBM protein improved feed utilization.KEY WORDS

An 8w growth trial was conducted to determine the effect of partial replacement of fish meal (FM) by a blend of rendered animal protein (BAP, comprised of 40% meat and bone meal, 40% poultry by‐product meal, 20% hydrolyzed feather meal in diets for juvenile Siberia sturgeon (Acipenser baerii Brandt). Five experimental diets were formulated. The control diet (C) contained 48% FM, whereas in the remaining four diets, FM were replaced by BAP at 25% or 50% level balanced by crystallized amino acid (AA) or spray‐dried blood meal (BM), which named as BAP25‐AA, BAP25‐BM, BAP50‐AA and BAP50‐BM, respectively. Weight gain rate of BAP50‐AA group was significantly higher than that of C group, while other BAP diets did not show negative effect on growth performance. The BAP25‐BM group exhibited the lowest feed conversion rate (FCR) (P < 0.05). FM replacement by BAP did not affect chemical composition of the whole body and crude fat level of the liver, but significantly affect the fillet lipid content. Hepatic aspartate aminotransferase and serum total protein, total cholesterol and triglyceride were reduced in fish fed diet BAP50B. Siberian sturgeon showed high efficiency on utilization of crystalline amino acid as good as those from BM.

Apparent digestibility coefficients (ADCs) of dry matter (ADC d ), crude protein (ADC p ), energy (ADC e ) and amino acids in selected feedstuffs were determined for juvenile Siberian sturgeon (8.38 ± 0.20 g). The tested feedstuffs were fishmeal (FM), meat and bone meal (MBM), poultry by-product meal, hydrolysed feather meal, fermented feather meal solvent-extracted cottonseed meal and soybean meal. ADCs were determined using a reference diet and test diets at 7 : 3 ratios with 5 g kg )1 chromic oxide (Cr 2 O 3 ) as an inert marker. Fish were reared in a recirculating system and fed to apparent satiation five times daily. Cr 2 O 3 in diets and faeces samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and aciddigestion colorimetry (AC) methods, respectively. The results showed that ICP-AES method was more accurate for Cr 2 O 3 determination than AC method, and the results determined by ICP-AES method were used in this study. ADC d and ADC p of seven tested ingredients were lowest for MBM (59.1 and 84.5%) and highest for FM (79.9 and 94.5%); ADC e of tested ingredients were from 71.8% for SECM to 93.2% for FM. ADCs of amino acid in test ingredients followed similar trend to the ADC p . The ADCs of individual amino acids varied from 61.6% (histidine in MBM) to 98.8% (valine in FM). KEY WORDS

A 56‐day feeding trial was conducted to investigate the effects of replacing fish meal (FM) with soybean meal (SBM) and fermented soybean meal (FSBM) on growth performance, nutrition utilization and intestinal histology of largemouth bass. The basal diet contained 350 g/kg FM (control), and then, FM was replaced with SBM or FSBM of 15%, 30%, 45% and 60% respectively. The results showed that the specific growth rate of fish fed FSBM‐60, SBM‐45 and SBM‐60 diets significantly decreased, and the feed conversion ratio of SBM‐30, SBM‐45, SBM‐60, FSBM‐45 and FSBM‐60 groups increased when compared to the control group (p < .05). The apparent digestibility coefficients of dry matter and crude protein of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05), and the substitution of FM with SBM and FSBM (45% and 60%) significantly reduced the protein retention (p < .05). Serum total protein contents of SBM‐60 and FSBM‐60 groups and serum cholesterol contents of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05). The SBM‐30 and SBM‐60 groups showed significantly higher alanine aminotransferase activity than the control group (p < .05). The intestinal histology analysis resulted that the villus length of the SBM‐60 group and the villus width of the SBM‐45, SBM‐60 and FSBM‐60 groups decreased when compared to the control (p < .05). In conclusion, FSBM could replace 30% FM in diet of largemouth bass containing 350 g/kg FM, while the substitution level of FM with SBM was only 15%.

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