Growth performance and TOR pathway gene expression of juvenile blunt snout bream,Megalobrama amblycephala,fed with diets replacing fish meal with cottonseed meal

A 16‐week feeding trial was conducted to assess the effects of replacing fish meal (FM) with cottonseed meal (CM) on the growth performance, feed utilization, plasma biochemical composition and target of rapamycin (TOR) pathway gene expression of juvenile blunt snout bream (Megalobrama amblycephala). Five isonitrogenous (36% crude protein) and isoenergetic (16 MJ kg^?1) diets with graded replacing levels of CM (replacing 0, 25, 50, 75 and 100% FM with CM) and similar lysine and methionine concentrations were fed to triplicate groups of fish. Results revealed that specific growth rate (SGR), feed intake and protein efficiency ratio (PER) of group fed with diets replacing FM with CM up to 50% were significantly higher than others (P < 0.05). However, final body weight and feed conversion ratio (FCR) remained similar up to 25% and thereafter significantly decreased and increased, respectively, as the replacement level increased (P < 0.05). Replacement levels significantly decreased hepatosomatic index and viscerosomatic index (P < 0.05), but did not significantly affect condition factor and whole body compositions. Free gossypol mainly accumulated in liver and significantly increased in diets CM75 and CM100 than CM0 (P < 0.05). Replacement significantly influenced plasma urea contents (P < 0.05). Meanwhile, increasing replacement of FM with CM in diets increased insulin‐like growth factor I (IGF‐1) gene expression in liver of blunt snout bream. Target of rapamycin (TOR) gene expression in diet CM100 was significantly lower than that in diets CM0 and CM75, while the eukaryotic translation initiation factor 4E‐binding protein 2 (4E‐BP2) gene expression was not affected by the replacement level of CM in diets. Therefore, based on final body weight and FCR, it suggested that up to 25% of FM (150 g kg^?1 in basal diet) could be replaced by CM in diets, which was 112.5 g kg^?1 FM and 192.9 g kg^?1 CM, for juvenile blunt snout bream.     

Effects of the total fish meal replacement by soybean meal on growth parameters,serum biochemistry,and hepatic and intestinal histology of juvenile blunt snout bream (Megalobrama amblycephala)

ABSTRACT

Fish meal is the main protein source in fish diet, but due to its unsustainability, it has to be replaced with more sustainable protein sources, such as soybean meal (SBM), in fish feeds. As SBM often produces negative effects on fish growth and health, we conducted an eight-week trial of complete fish meal replacement with SBM in the diet of juvenile (48.2 ± 0.55 g) blunt snout bream (Megalobrama amblycephala), a herbivorous cyprinid fish native to the Yangtze basin (China). SBM-fed fish exhibited: a worsened growth performance; improved survival rate (P > 0.05); elevated serum triglycerides and total cholesterol but reduced low-density lipoprotein in plasma (P < 0.05); mild lipid droplet accumulation and swelling of the liver; elevated goblet cell counts and mild signs of enteritis in the intestines. With negligible effects on growth and mild effects on health, M. amblycephala appears to be comparatively tolerant of SBM, but total fish meal replacement is not recommended. Future studies should aim to identify the SBM tolerance threshold in long-term growth trials.     

Graded replacing fishmeal with canola meal in diets affects growth and target of rapamycin pathway gene expression of juvenile blunt snout bream,Megalobrama amblycephala

A feeding trial was conducted to assess the effects of replacing fishmeal (FM) with canola meal (CM) on the growth performance, feed utilization and related gene expression of juvenile blunt snout bream (Megalobrama amblycephala). Fishes were fed with five isonitrogenous (330 g/kg crude protein) and isoenergetic (15 MJ/kg) diets for 16 weeks, which was graded replacing levels of fishmeal (replacing 0, 37.5, 75, 112.5 and 150 g/kg FM with CM). The results revealed that specific growth rate, feed efficiency ratio and protein efficiency ratio of the groups with replacement level up to half were significantly higher than the others, while feed intake was inverse. Peptide transporter 1 (PepT1) mRNA level in the gut was significantly up‐regulated in groups CM25 and CM50 compared to other groups. Relative gene expression of IGF‐1 among groups was extremely significant based on the nonparametric test. Replacement of FM with CM caused a reduction in the hepatic expression of target of rapamycin (TOR), while significant increase trends were observed in hepatic genes of protein kinase B (AKT) and eIF4‐binding protein (4E‐BP2). However, TOR gene expression in the gut was significantly up‐regulated first and then down‐regulated, while mRNA levels of 4E‐BP2 and S6K1 in the gut were first significantly decreased and then increased in CM75, finally significantly decreased to the lowest. The overall results indicated that up to 75 g/kg FM could be replaced by CM (350.5 g/kg CM) in the diets for juvenile blunt snout bream. Besides, these signalling molecules could explain further the mechanisms that juvenile blunt snout can only maintain optimal growth performance up to 75 g/kg FM replacement with CM.     

Growth and body composition of rohu (Labeo rohita) fed diets containing oilseed meals: partial or total replacement of fish meal with soybean meal

A 56‐day feeding trial was conducted to evaluate growth, feed utilization and body composition of fingerling rohu, Labeo rohita (4.5 ± 0.2 cm; 2.58 ± 0.04 g), fed five isonitrogenous (350 g kg^?1 crude protein) and isoenergetic (15.7 kJ g^?1 metabolizable energy) diets in which the main protein contributors were: diet I, fish meal (FM); diet II, soybean meal (SBM); diet III, groundnut meal (GNM); diet IV, equal amounts of SBM, GNM and canola meal (CM); diet V, equal amounts of FM, SBM, GNM and CM. Fish were stocked in triplicate groups of 25 fish held in 70 L flow‐through tanks (water volume 55 L) and fed twice daily (0900 and 1700 hrs) to apparent satiation. Fish fed diet I exhibited the highest (P < 0.05) values for live weight gain and specific growth rate (% per day). Feed conversion and protein efficiency ratio were better (P < 0.05) in fish‐fed diets I and II. Fish‐fed diet II exhibited lower (P < 0.05) fat and ash contents in carcass. Based on these findings, a 70‐day trial (Experiment II) was conducted with six diets fed under the same conditions where FM was incrementally replaced with SBM. Fingerling L. rohita (6.7 ± 0.4 cm; 4.07 ± 0.02 g) were used for the study. Crystalline l ‐methionine was added to diets containing more than 250 g kg^?1 SBM. This second study showed no significant (P > 0.05) variation in growth, feed utilization and carcass composition for fish fed the different diets. In conclusion, SBM was more effective than GNM or CM, as FM was replaced in feeds for fingerling L. rohita and could completely replace FM when supplemented with methionine and fortified with minerals under the conditions of this study.     

Response of juvenile tench (Tinca tinca L.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90‐day trial with 5‐month‐old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.     

Growth, feed efficiency and body mineral composition of juvenile vundu catfish (Heterobranchus longifilis, Valenciennes 1840) in relation to various dietary levels of soybean or cottonseed meals

This study aimed to assess the effect of soybean meal (SBM) and cottonseed meal (CSM), as partial replacement of dietary fish meal on growth, feed efficiency (FE) and body mineral composition of juvenile vundu (Heterobranchus longifilis). Five iso‐nitrogenous (390 g kg^?1 crude protein) and iso‐caloric (18 kJ g^?1, gross energy) diets (Control, SBM30, SBM60, CSM30 and CSM60) were fed to triplicate groups of 40 fish (initial mean weight: 12 g) in each tank (0.9 m³). Over a 7‐week feeding period, significant differences (P < 0.05) were observed on growth, FE and body mineral composition between treatments. Fish‐fed CSM‐based diets and 600 g kg^?1 SBM‐based diet had reduced growth and reduced feed and protein efficiencies when compared with those fed diet containing 300 g kg^?1 SBM or the control diet. Data from body mineral composition in response to dietary treatment could be divided into two groups. The first group refers to elements such as Mg and Fe for which carcass and fillet composition did not show significant differences with dietary level of SBM or CSM. Ca, P, K, Zn and Mn composed the second group of minerals whose concentrations in fish body were significantly reduced in fish‐fed SBM60. In conclusion, the results of this study indicate that although solvent‐extracted SBM and CSM are often reported safe for fish, they can only partially replace fish meal as a source of protein in compound feed for vundu at a limited amount between 300 and 600 g kg^?1 for SBM and <300 g kg^?1 for CSM.     

Effect of partial replacement of dietary fish meal by soybean meal with betaine attractant supplementation on growth performance and fatty acid profiles of juvenile rainbow trout (Oncorhynchus mykiss)

This study was conducted to investigate the effects of dietary incorporation of soybean meal for fish meal replacement and supplementation of betaine as an attractant on growth performance and fatty acid profiles of rainbow trout (Oncorhynchus mykiss). Juvenile trout were fed practical diets, with increasing soybean levels and betaine supplementations. The experimental diets consisted of a control diet with fish meal as the sole protein source (control) and no attractant, 25% soybean‐1% betaine diet (SBM25‐B1), 50% soybean‐2% betaine diet (SBM50‐B2), and 50% soybean‐0% betaine diet (SBM50‐B0). Average body weight was 12.69 ± 0.16 g at the beginning of experiments. Following 54 days feeding programme with experimental diets, average body weights reached 47.45 ± 1.22 g, 58.11 ± 1.77 g, 56.34 ± 1.87 g and 53.76 ± 1.74 g in the control, SBM25‐B1, SBM50‐B2 and SBM50‐B0 groups respectively. As compared with control treatment, significant differences were observed in weight gain, specific growth rate and feed intake of 1% betaine treatment at 25% soybean‐meal‐incorporated diet (p < .05), but no differences were observed in feed conversation ratio and survival rates (p > .05). Compared with the control treatment, betaine‐supplemented groups had significantly higher total saturated fatty acid contents (p < .05). On the other hand, the control treatment showed a significantly higher level of monounsaturated fatty acid than the betaine‐supplemented groups (p < .05). Significant differences were observed in fatty acid profile of 1% betaine‐supplemented group (p < .05) compared with the control. Present findings revealed that 1% betaine supplementation with dietary incorporation of soybean meal at 25% level positively influenced growth performance, feed utilization and fatty acid profiles of rainbow trout juveniles.     

Effects of xylan and cottonseed meal on growth performance,digestion, intestinal morphology and the expression of two peritrophin genes of Chinese mitten crab,Eriocheir sinensis

Xylan is one of the main non‐starch polysaccharides (NSPs) in cottonseed meal. This study aimed to evaluate the anti‐nutrition effect of xylan and to better understand cottonseed meal as a feed ingredient for the Chinese mitten crab, Eriocheir sinensis. A diet containing 280 g/kg fishmeal without cottonseed meal or xylan was formulated as a control (FM diet). A second diet (XYL diet) was supplemented with 53.3 g/kg xylan according to its amount in the third diet, the cottonseed meal diet (CSM diet), which was formulated to include 400 g/kg cottonseed meal. The last diet (CSM + XYLase diet) included 400 g/kg xylanase hydrolysed cottonseed meal, in which most xylan was hydrolysed. Diets were isonitrogenous (370 g/kg crude protein) and isoenergetic (17.58 KJ/g) and were randomly fed to 12 tanks of crabs for 8 weeks. Results showed that no difference was detected among groups in growth performance, serum biochemical index, or digestive and metabolism enzyme activity (p > 0.05). The apparent digestibility coefficient (ADC) of dry matter was FM > XYL > CSM + XYLase > CSM (p < 0.05). The ADC of protein in crab fed diet FM and XYL was significantly higher than CSM and CSM + XYLase (p < 0.05). Cottonseed meal decreased the fold height of the hindgut, upregulated the expression of peritrophin genes of Es‐PL44 and Es‐PP1 (p < 0.05), while xylan decreased the fold height of the hindgut and upregulated the expression of Es‐PP1 (p < 0.05). These results indicated that the negative effect of cottonseed meal and xylan on digestibility partly compensated by enhanced absorption of the hindgut innerly and by supplementation of xylanase externally, and cottonseed meal is an attractive alternative protein source in general for Chinese mitten crab.     

Partial substitution of fish meal with soybean and cottonseed meals in diets for African bonytongue,Heterotis niloticus (Cuvier, 1829) fingerlings: effects on growth,feed efficiency and body composition

A feeding trial was conducted to examine the suitability of soybean meal (SBM) and cottonseed meal (CSM) as a partial substitute for the dietary protein supplied by fish meal for H. niloticus fingerlings. Fish were fed with four isonitrogenous (350 g kg^?1 crude protein) and isoenergetic (18.8 kJ g^?1 GE) diets in which fish meal protein was gradually replaced by plant protein from a mixture of SBM and CSM (0%, 25%, 50% and 75% in diets 1, 2, 3 and 4 respectively). Triplicate groups of fingerlings H. niloticus (mean weight of 5 g) were handfed twice daily to apparent satiation for 60 days inside net hapas. Growth performances (SGR varied from 3.09% to 3.16% day^?1) of fingerlings fed diets containing 0%, 25% and 50% plant protein were not significantly different (P>0.05). At 75% fish meal substitution, growth and feed utilization efficiency indicators were significantly reduced (P<0.05). The carcass composition were also significantly (P<0.05) affected by the replacement level of fish meal, except dry matter and ash. Results suggest that the dietary fish meal protein could efficiently be substituted by a mixture of soybean and cottonseed meals up to 50%, without adverse effects on maximal growth in practical diets for H. niloticus fingerlings.     

Effects of dietary carbohydrate/lipid ratios on growth performance,body composition and glucose metabolism of fingerling blunt snout bream Megalobrama amblycephala

This study aimed to investigate the optimum dietary carbohydrate/lipid (CHO/L) ratio for fingerling blunt snout bream Megalobrama amblycephala (average initial weight: 6.61 ± 0.03 g). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO/L ratios ranging from 1.62 to 24.20. Each diet was tested in four replicates for 10 weeks. Specific growth rate (SGR), feed conversion ratio and nitrogen and energy retention all improved significantly (P < 0.05) as dietary CHO/L ratios decreased from 24.20 to 5.64 but showed little difference (P > 0.05) as dietary CHO/L ratios ranged from 2.45 to 5.64. Hepatosomatic index increased significantly (P < 0.05) as dietary CHO/L ratios increased, whereas intraperitoneal fat ratio showed an opposite trend (P < 0.05). Opposite to moisture content, lipid content of whole body and carcass all increased significantly (P < 0.05) as dietary CHO/L ratios decreased. Liver lipid content showed little difference (P > 0.05) among all the treatments, while liver glycogen content increased significantly (P < 0.05) with increasing CHO/L ratios. High dietary carbohydrate enhanced the activities of liver hexokinase, pyruvate kinase and glucose‐6‐phosphate dehydrogenase but did not induce hyperglycaemia. Based on the second‐order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling blunt snout bream were 291.7 and 81.4 g kg⁻¹, respectively, with a corresponding dietary CHO/L ratio of 3.58.     

Partial replacement of fish meal by a mixture of soybean meal and rapeseed meal in practical diets for juvenile Chinese mitten crab Eriocheir sinensis: effects on growth performance and in vivo digestibility

An 8‐week experiment was conducted to examine the effect of partial replacement of fish meal (FM) by a mixture of soybean meal (SBM) and rapeseed meal (RM) in practical diets of juvenile Chinese mitten crab Eriocheir sinensis of initial body weight of 1.54±0.12 g (means±SD, n=90). Five isonitrogenous diets were formulated to contain 35% protein and 5% lipid. Soybean meal and RM mix (1:1 ratio) were included at five levels of 0 (control), 15%, 30%, 45% and 60%, replacing 0, 20%, 40%, 60% and 80% FM respectively. When FM was replaced by 15% of SBM and RM, crab showed the highest growth, feed utilization and moulting frequency (MF). Fish meal replaced by SBM and RM did not significantly influence crude protein, lipid and moisture contents of whole body crab, but ash content was the lowest for crab fed the diet with FM replaced by 15% of SBM and RM. Apparent digestibility coefficients (ADCs) of dry matter, crude protein and energy tended to decline with increasing inclusion levels of dietary SBM and RM. In general, ADCs of lipid were high (over 90%) and showed no significant differences among the treatments (P>0.05). Based on these observations above, these results indicated that about 40% of FM can be replaced with a mixture of SBM and RM (1:1 ratio) in the diet of E. sinensis without adverse growth performance, compared with the FM‐based diet. However, 20% of FM replaced by SBM and RM produced the best growth performance and feed utilization.     

Effect of replacing fish meal with soybean meal on growth,feed utilization and nitrogen and phosphorus excretion of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth, feed utilization, and nitrogen (N) and phosphorus (P) excretion of juvenile Pseudobagrus ussuriensis (initial average weight 0.50 ± 0.00 g). Seven isonitrogenous and isolipidic diets were formulated to contain SBM to replace fish meal protein at 0% (S0), 10% (S10), 20% (S20), 30% (S30), 40% (S40), 50% (S50) and 60% (S60) respectively. To investigate the effects of supplementation with crystalline amino acid to balance diet S60, one diet was formulated to add 0.30% methionine (SM60). The results showed that there was no significant difference in weight gain among fish fed S0, S10, S20, S30 and S40 diets, however, a significant reduction in this variable occurred when 50% and 60% of fish meal protein was replaced by SBM (P < 0.05). Apparent digestibility coefficients of dry matter, crude protein and phosphorus of diets were affected by dietary SBM levels. N and P excretion indicate that fish meal replacement by SBM led to an increase in N excretion, but led to a reduction in P excretion. No differences were detected in growth, feed utilization and N and P excretion between fish feed diets S60 and SM60. The results of this study show that 40% of fish meal protein could be replaced by SBM in diets of juvenile P. ussuriensis without having a significant negative effect on growth or feed efficiency, but that higher dietary SBM levels reduce fish performance.     

Complete replacement of fish meal by plant protein ingredients with dietary essential amino acids supplementation for juvenile blunt snout bream (Megalobrama amblycephala)

Six extruded diets were formulated with a graded level of fish meal (FM); diet 1 and diet 2 were formulated with 80 g/kg FM; diet 3 and diet 4 were formulated with 40 g/kg FM; and diet 5 and diet 6 were devoid of FM. Hence, diet 2, diet 4 and diet 6 were supplemented with essential amino acids (EAAs). The diets were fed throughout an eight‐week feeding trial. The results revealed that specific growth rate (SGR), feed conversion ratio (FCR), body weight gain (BWG) and protein efficiency ratio (PER) were influenced by FM reduction and improved by the addition of EAA (p < 0.05). A survival rate (SR), whole body content of protein, lipid, moisture and ash, and plasma total protein (TP), albumin (ALB), triglyceride (TG) and urea (UN) did not influence by dietary treatments (p > 0.05). Additionally, target of rapamycin (TOR) pathway did not influence by dietary treatments (p > 0.05). Expression levels of hepatic peptide transporter 1 (Pept1) and peptide transporter 2 (Pept2) decreased against FM reduction and improved significantly in the groups fed diet 4 and diet 6. In summary, the findings revealed that diet containing plant proteins mixture supplemented with EAA could totally replace FM in the practical diet of blunt snout bream.     

Effect of replacing soybean meal with canola meal on growth,feed utilization and haematological indices of juvenile hybrid tilapia,Oreochromis niloticus×Oreochromis aureus

An 8‐week feeding trial was conducted to evaluate the effects of replacing soybean meal (SBM) with canola meal (CM) on growth, feed utilization, body composition and haematological indices of juvenile hybrid tilapia (Oreochromis niloticus×Oreochromis aureus). Six isonitrogenous diets containing graded levels of CM (0, 95, 190, 285, 380 and 634 g kg^?1 of diet corresponding to 0%, 15%, 30%, 45%, 60% and 100%, respectively, of protein from SBM) to replace SBM on an equal protein basis were fed to triplicate groups of juvenile fish (initial weight=6.3 g). The results indicated that up to 30% of SBM could be replaced by CM without causing a significant reduction in growth performance. Fish fed with diets in which CM replaced over 45% of SBM had a significantly lower protein efficiency ratio and a significantly higher feed conversion ratio than fish fed with other diets. The apparent digestibility coefficients (ADC) of dry matter, protein and phosphorus were lowest for fish fed the CM100 diet. Significant differences in haemoglobin, haematocrit and white blood cell concentration were found in fish fed diets with different CM levels. It is concluded that up to 19.02% CM can be used to replace 30% of SBM in diets for juvenile hybrid tilapia without compromising growth, feed conversion and protein utilization.     

团头鲂对饲料中Zn的需求量

为了研究团头鲂对饲料中Zn的需要量,以平均体质量50 g的团头鲂为实验对象,采用半纯化饲料,以ZnSO4·H2O为锌源,设置Zn添加量分别为0、68、137、206、275 mg/kg(饲料中Zn总量为22.85、98.07、164.00、235.43、307.96 mg/kg)共5个Zn含量梯度,每个实验组设4个平行,在池塘网箱中养殖43 d。经过回归拟合分析,饲料中Zn添加量、饲料中Zn总量与团头鲂特定生长率、饲料系数、蛋白质沉积率、脂肪沉积率的关系,得到团头鲂对饲料中无机Zn补充量为155.86~161.25 mg/kg,对饲料总Zn需要量为184.85~190.39 mg/kg;在日均摄食量为5.12 g/100 g体质量下,团头鲂对饲料Zn日需求量为0.798~0.825 mg/100 g体质量,对饲料总Zn日需要量为0.946~0.974 mg/100 g体质量。饲料中Zn含量对团头鲂的成活率、肥满度、内脏指数、鳞片重/体质量、体质量/体长、脊椎骨重/体质量无显著影响(P0.05)。饲料中Zn含量对团头鲂的脊椎骨长/体长有显著影响(P0.05);饲料中Zn的补充,有利于团头鲂脊椎骨的生长。     

饲料锌对团头鲂幼鱼生长性能、血清生化指标和抗氧化功能的影响

以酪蛋白和明胶为蛋白源,七水硫酸锌(Zn SO4·7H2O)为Zn源,分别配制成7种Zn含量(7.4 mg/kg、20.3 mg/kg、32.1 mg/kg、51.0 mg/kg、84.4 mg/kg、169.7 mg/kg、332.4 mg/kg)的半纯化饲料,投喂初始体重为(3.6±0.1)g团头鲂(Megalobrama amblycephala)12周,考察Zn对团头鲂幼鱼生长性能、血清生化指标和抗氧化功能的影响,确定团头鲂幼鱼对饲料Zn的需要量。结果表明,随着饲料Zn含量增加,团头鲂增重率、特定生长率和全鱼Zn含量呈先增加后稳定的趋势;全鱼水分含量显著降低(P0.05),粗蛋白含量显著增加。饲料Zn含量对团头鲂饲料系数无显著影响。饲料中添加Zn显著影响血清总蛋白、尿素氮、高密度脂蛋白胆固醇、总胆固醇以及甘油三酯含量,而对血清白蛋白含量和碱性磷酸酶活性无显著影响。随着饲料中Zn含量的增加,团头鲂肝丙二醛含量显著降低(P0.05),而肝过氧化氢酶和超氧化物歧化酶活性在各处理间均无显著差异。折线回归分析表明,团头鲂幼鱼(体重3.6~26.7 g)获得最佳生长时对饲料Zn需要量为32.6 mg/kg,获得最大鱼体Zn含量时Zn的需要量为47.6 mg/kg。本研究旨在确定团头鲂幼鱼对饲料中Zn的需要量,为配制团头鲂高效环保饲料提供科学依据。     

An evaluation of replacing fish meal with fermented soybean meal in the diets of largemouth bass (Micropterus salmoides): Growth,nutrition utilization and intestinal histology

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%.     

Effects of dietary inclusion of soybean meal and cholesterol on the growth,cholesterol status and metabolism of the giant grouper (Epinephelus lanceolatus)

The study evaluated effects of cholesterol supplementation in a diet with high soybean meal (SBM) on the growth and cholesterol metabolism of giant grouper (Epinephelus lanceolatus). All‐fish‐meal diet was used as control. The diet including SBM (replaced 50% of the fish meal protein, SBM diet) and the SBM diet supplemented with 10 g/kg cholesterol (SBM + cholesterol) were used as experimental diets. Three diets were each fed to triplicate groups of juvenile grouper (initial body weight: 12.39 ± 0.36 g) in a recirculating aquaculture system for 8 weeks. Grouper fed the control diet showed higher (p < .05) weight gain, feed intake, feed efficiency and protein efficiency ratio than the other two dietary treatments. Hepatic cholesterol concentrations and 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase gene expressions were higher in fish fed the control diet than fish fed the control diet and SBM + cholesterol diet. Hepatic cholesterol 7α‐hydroxylase gene expression was higher in fish fed the SBM + cholesterol diet than that in fish fed the control diet. Results indicate that giant grouper on a diet low in cholesterol can regulate cholesterol synthesis, suggesting that the reduced dietary cholesterol intake in the fish fed diet containing SBM is sufficiently compensated by increased cholesterol synthesis.     

Effects of complete fish meal replacement by rice protein concentrate with or without lysine supplement on growth performance,muscle development and flesh quality of blunt snout bream (Megalobrama amblycephala)

An 8‐week feeding trial was conducted to evaluate the effects of fish meal (FM) replacement by rice protein concentrate (RPC) with supplementation of microcapsule lysine (ML) or crystalline lysine (CL) on growth performance, muscle development and flesh quality of blunt snout bream. Four isonitrogenous and isoenergetic diets were formulated, including FM diet (containing 50 g/kg FM), RPC diet (FM replaced by RPC), MRPC diet (FM replaced by RPC with ML supplementation) and CRPC diet (FM replaced by RPC with CL supplementation). Fish fed FM diet had significantly higher weight gain, feed efficiency, protein efficiency ratio and nitrogen and energy utilization than that of RPC group, but showed no statistical difference with other treatments. In addition, fish fed RPC diet showed higher muscle fibre frequency in the 20‐ to 50‐μm class but lower >50‐μm class and higher cooking loss than that of the other groups. Furthermore, no significant difference was found in whole‐body proximate compositions, frequency distribution of <20‐μm‐diameter fibres, texture, muscle content, collagen, pH 24 hr post‐mortem and sensory quality. The results showed that RPC supplemented with ML or CL could replace fishmeal without any adverse effects on growth performance and flesh quality for blunt snout bream.     

Effects of natural feeding stimulants and glutamic acid supplementation on the feed intake,growth performance and digestive enzyme activities of red sea bream (Pagrus major) fed fish meal‐free soy protein concentrate (SPC)‐based diet

Two experiments were conducted for red sea bream (Pagrus major). In experiment 1, the optimum level of glutamic acid and natural feeding stimulants to enhance feed intake were determined and found that glutamic acid level of 0.5% and fish meat hydrolysate (FMH) were effective. In experiment 2, fish were fed with soy protein concentrate (SPC)‐based diet with synthetic feeding stimulants (Basal diet), the Basal diet with FMH (FMH diet), the FMH diet with glutamic acid (FMHG diet) and with fish meal diet (FM diet) as a control until satiation for 8 weeks. Feed intake of FMHG‐fed fish was significantly higher than others (p < 0.05). Specific growth rate and the feed conversion ratio of FMHG were comparable to those of FM‐fed fish (p > 0.05). Relative visceral fat ratio and crude lipid content of any SPC‐based diet‐fed fish tended to be lower than those of FM diet‐fed fish. There were no significant differences in trypsin and lipase activities hepatopancreas among treatments. SPC can be utilized as a sole protein source in a diet for red sea bream. The lower growth performance in SPC‐based diet‐ fed fish was not due to poor digestive enzyme secretion but could be associated with lipid utilization disorder.