Influence of soya saponin, soya lectin, and cholyltaurine supplemented to a casein-based semipurified diet on intestinal morphology and biliary bile status in fingerling rainbow trout Oncorhynchus mykiss

To investigate the cause of the changes in intestinal morphology and biliary bile status of rainbow trout Oncorhynchus mykiss fed defatted soybean meal (SBM)-based diets, casein-based semipurified diets supplemented with soya saponin, soya lectin, and cholyltaurine were fed to rainbow trout for 6 weeks. An unsupplemented control diet and a SBM-based diet were also tested as references. Poor development of microvilli and pinocytotic vacuoles, and accumulation of large vacuoles in the epithelial cells were observed in the distal intestine of fish fed diets containing saponin but not cholyltaurine. Hyperplastic connective tissue in the mucosal folds of the distal intestine was observed in fish fed a diet containing both saponin and lectin but not cholyltaurine. However, intestinal histological features in fish fed diet supplemented with cholyltaurine and lectin and/or saponin were similar to those in the control diet group. Liver morphology and biliary bile status were not affected by saponin and lectin. These results suggest that the abnormal features of the distal intestine of rainbow trout fed SBM-based diets are caused by the combination of soya saponin and soya lectin, and that supplemental cholyltaurine plays certain roles in normalizing the intestinal abnormalities caused by the saponin and lectin.     

Supplemental effect of cholyltaurine and soybean lecithin to a soybean meal-based fish meal-free diet on hepatic and intestinal morphology of rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

The supplemental effects of cholyltaurine and soybean lecithin to a defatted soybean meal (SBM)-based fish meal-free diet on the hepatic and intestinal morphology of rainbow trout Oncorhynchus mykiss were investigated. A fish meal-based diet (FM), three fish meal-free diets supplemented either with soybean lecithin (SL), bovine gall powder (BG) or cholyltaurine (C-tau) and an unsupplemented fish meal-free diet (NFM), were given to fish (−11 g) for 10 weeks. The growth was the lowest in fish fed diet NFM, intermediate in fish fed diet SL and the highest in fish fed diet FM, BG and C-tau. Hepatocytes of fish fed diet NFM were atrophied, and the distal intestine of these fish showed abnormal features: disintegrated microvilli and fatty degeneration in epithelial cells and increased amount of connective tissue in the submucosa. Hepatic and intestinal histological features in fish fed diets SL, BG and C-tau were similar to those in fish fed diet FM. These results indicate that soybean lecithin, bovine bile salts and cholyltaurine have similar effects on normalizing the hepatic and intestinal morphologies of rainbow trout fed the SBM-based diet, although growth promotion effect was limited in the soybean lecithin.     

Effects of biotechnologically processed soybean meals in a nonfishmeal diet on growth performance, bile acid status, and morphological condition of the distal intestine and liver of rainbow trout Oncorhynchus mykiss

This study evaluated four commercially available biotechnologically processed soybean meals (SBMs) that were included as the primary protein sources in a nonfishmeal diet for juvenile rainbow trout Oncorhynchus mykiss. The processed SBMs were Afcep SBM fermented with mixed bacteria predominantly Bacillus spp., DaBomb SBM fermented with Lactobacillus acidophilus, PepSoyGen SBM fermented with Aspergillus oryzae and Bacillus subtilis, and HP300 SBM treated enzymatically. Fishmeal (FM) and common heat-treated and hulled SBM were used in the reference diets. Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) analysis revealed that the protein components of Afcep SBM appeared to have relatively small molecular sizes compared with the other SBM products. After a 10-week feeding trial, growth of fish fed the common SBM diet was depressed, and abnormal liver and distal intestinal morphologies and bile acid characteristics were observed. The Afcep SBM diet showed approximated growth performance and comparable physiological conditions relative to the FM diet, while only limited improvements were observed in fish fed the other processed SBMs. These findings suggest that Afcep SBM, with its smaller molecular mass proteins, is the most promising processed SBM in nonfishmeal diets for rainbow trout.     

Effect of soybean meal,raffinose and stachyose on the growth,body composition,intestinal morphology and intestinal microflora of juvenile allogynogenetic silver crucian carp (Carassius auratus gibelio♀×Cyprinus carpio♂)

The study was conducted to investigate the effects of soybean meal (SBM), raffinose and stachyose on juvenile crucian carp (Carassius auratus gibelio♀ × Cyprinus carpio♂). The experimental diets consisted of one control diet based on fish meal (FM), one diet containing 300 g kg^?1 SBM and four FM‐based diets with the addition of either 6.7 g kg^?1 raffinose (Raf), 33.9 g kg^?1 stachyose (Sta), a combination of raffinose and stachyose (Raf?Sta) and finally a Raf?Sta diet supplemented with 2.5 g kg^?1 saponins (Raf?Sta?Sap). After 3 weeks of feeding, the relative gut lengths of SBM‐fed fish and the fish fed stachyose‐containing diets were shorter than those of the FM‐fed fish; further, more SBM‐fed fish showed fissures on the tips of the intestinal folds. After 8 weeks of feeding, the growth of SBM‐fed fish was significantly lower than that of FM‐fed fish (P<0.05). The fish fed Raf?Sta?Sap had a low relative gut length (P<0.05). In comparison with the other fish, the SBM‐fed fish had a higher number of large‐sized homogeneous vacuoles in the cytoplasm of epithelial cells and shorter microvilli. No significant difference was observed in body composition or intestinal microflora. The results indicated that raffinose and stachyose played no or only minor roles in the development of soybean‐induced growth reduction.     

Feeding fermented soybean meal diet supplemented with taurine to yellowtail Seriola quinqueradiata affects growth performance and lipid digestion

Feeding experiment was conducted to determine whether fermentation and taurine supplementation of soybean meal (SBM) fed to yellowtail improve growth performance and lipid digestion. Six diets were formulated and designated as SBM, SBM supplemented with taurine (SBM + T), SBM fermented by Bacillus spp. (FSBM1), SBM fermented by Lactobacillus spp. (FSBM2), FSBM2 supplemented with taurine (FSBM2 + T), and fish meal (FM). Yellowtail fingerlings with an initial body weight of 42 g were stocked in 200‐L tanks. The fish were fed, each diet was fed twice daily in two separate tanks for 8 weeks. Results showed that lipid digestibility of the SBM diet was significantly lower than that of the FM diet, but SBM diet lipid digestibility was improved by taurine supplementation and fermentation. Lipase activity in anterior intestinal digesta, lipid contents in liver and muscle, and bile acid concentrations in gallbladder and anterior intestinal digesta were significantly lower in fish fed SBM diet than in fish fed FM diet; these parameters were not significantly different between fish fed SBM + T, FSBM2, FSBM2 + T diets and FM diet. Although taurine supplementation or fermentation improved lipid digestibility compared with FM diet, growth parameters were only improved in the fish fed FSBM2 + T diet, indicating that apart from a lack of taurine, SBM contains other factors responsible for inferior growth of yellowtail. These factors can be partially eliminated by Lactobacillus spp. fermentation.     

Effects of soybean meal based diet on growth performance, gut histopathology and intestinal microbiota of juvenile rainbow trout (Oncorhynchus mykiss)

Effects of soybean meal (SBM) based diet on growth performance, histology of the intestinal epithelium and on the gut microbiota of juvenile rainbow trout (Oncorhynchus mykiss) were investigated on two trials lasting for 8 weeks (Trial I) and 18 weeks (Trial II). The microbiological characterization was done both with conventional plating techniques, biochemical profiling and length heterogeneity analysis of PCR amplified 16S rDNA (LH-PCR).Typical histological changes were found after 18 weeks of SBM feeding (Trial II). Mean height of simple foldings were significantly higher within the group fed with fish meal (FM) based diet. These changes were not, however, reflected in the appearance, behavior and weight gain of the fish, although the feed conversion rate (FCR) was higher, compared to fish fed with the traditional FM feed.In both SBM and FM groups the counts of cultivable intestinal bacteria dropped within the first 4 weeks of feeding (Trial I). Subsequently, the bacterial numbers increased in the FM group, but not in the SBM group by the 8th week of the trial. The LH-PCR data suggested also that diet-related qualitative changes in the microbiota had occurred (Trial II). The main identified bacteria were mainly representatives of the genera Aeromonas, Sphingomonas and Chryseomonas, and among the lactic acid bacteria, Lactococcus and Lactobacillus.Future research will be directed to the identification and eventual elimination the SBM-associated factors involved in the inflammatory responses and unfavorable FCR, in particular by modifying the intestinal microbiota.     

Influence of certain soybean antinutritional factors supplemented to a casein-based semipurified diet on intestinal and liver morphology in fingerling rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

To investigate the cause of morphological changes occurring in the liver and intestine of rainbow trout Oncorhynchus mykiss fed defatted soybean meal (SBM)-based non-fish meal diets, morphological observations were conducted on fish fed casein-based semipurified diets supplemented with soybean antinutritional factors (soya saponin, soya isoflavone, soya lectin, oligosaccharide, Ca-phytate and their mixture). Hepatocytes and the epithelial cells in the hepatic ducts were not atrophied in any of the treatments. Lack of microvilli and pinocytotic vacuoles, and fatty degeneration of the epithelial cells were observed in the distal intestine of fish fed diets containing soya saponin. The proliferation of connective tissue in the mucosal folds and submucosa was shown in the distal intestine of fish fed the diet containing all substances including lectin. These results suggest that both saponin and lectin are the responsible factors in SBM for the occurrence of morphological changes of the distal intestine in rainbow trout fed SBM-based diets.     

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%.     

The effect of plant‐based diet and suboptimal environmental conditions on digestive function and diet‐induced enteropathy in rainbow trout (Oncorhynchus mykiss)

This experiment investigated intestinal enteropathy and digestive function of rainbow trout challenged with soybean meal‐based diet (SBM) at optimal or suboptimal environments created by normal or reduced water flow, respectively. Oxygen level remained above 7 mg L^‐1 for optimal environment and between 4 and 5 mg L^‐1 for suboptimal environment. Triplicate groups of fish (mean body weight 74 g) were fed fishmeal‐based diet (FM) or SBM at optimal environment in period 1 (28 days). In period 2 (42 days), fish were subjected to a change from FM to SBM or remained on the same diet as used in period 1. The fish were also exposed to change from optimal to suboptimal environment or remained under optimal conditions. The fish subjected to change from FM to SBM, regardless of their environment, showed similar degree of enteropathy from day 14. Lipid and starch digestibility was lower in SBM‐fed fish at suboptimal environment compared to fish fed the same diet at optimal environment. Crude protein digestibility, however, was highest in SBM‐fed fish at suboptimal environment throughout period 2. In conclusion, in SBM‐fed rainbow trout, exposure to suboptimal environment did not change the degree of enteropathy; however, lipid and starch digestibility were further reduced.     

Effect of tributyrin supplementation in high‐soya bean meal diet on growth performance,body composition,intestine morphology and microbiota of juvenile yellow drum (Nibea albiflora)

Six equal‐protein and equal‐lipid diets were formulated: the fish meal (FM) diet, the soya bean meal (SBM) diet with 40% of FM protein replaced by SBM protein and tributyrin (TB) diets with 0.05% (TB0.05), 0.10% (TB0.1), 0.20% (TB0.2) and 0.40% (TB0.4) tributyrin supplemented in the SBM‐based diet. Each kind of diet was randomly fed to triplicate tanks with 20 fish per tank. Fish were fed apparent satiation twice daily for 56 days. No significant difference in weight gain rate (WGR) and feed efficiency rate (FER) was observed between fish fed the FM, TB0.1 and TB0.2 diets (p > .05). Muscle histidine and arginine proportion of fish fed TB0.1 diet was significantly higher than that of fish fed the SBM diet (p < .05). Intestine morphology results indicated that the supplementation of 0.1% tributyrin significantly improved the mucosal fold height, microvilli length and microvilli density when compared with those of fish fed the SBM diet (p < .05). The supplementation of dietary tributyrin suppressed the pro‐inflammatory gene expression, which may be due to the improvement of physical barrier and modification of microbial communities, such as Acinetobacter, Rhodocyclaceae, Brevundimonas, Sphingopyxis, Hydrogenophaga, Methyloversatilis and Devosia. In conclusion, dietary 0.1% tributyrin supplementation in high‐soya bean meal diet improved growth performance, flesh quality and intestinal morphology structure integrity of yellow drum.     

Effects of replacing fish meal with soybean meal and peanut meal on growth,feed utilization and haemolymph indexes for juvenile white shrimp Litopenaeus vannamei,Boone

An 8‐week feeding trial was conducted to evaluate the effects of replacing fish meal (FM) with soybean meal (SBM) and peanut meal (PM) on growth, feed utilization, body composition and haemolymph indexes of juvenile white shrimp Litopenaeus vannamei, Boone. Five diets were formulated: a control diet (FM30) containing 30% fish meal and four other diets (FM20, FM15, FM10 and FM5) in which protein from fish meal was substituted by protein from SBM and PM. The dietary amino acids of diets FM20, FM15, FM10 and FM5 were equal to those of the diet FM30 by adding crystalline amino acids (lysine and methionine). Each diet was randomly assigned to triplicate groups of 30 shrimps (initial weight = 0.48 g), each three times daily. The results indicated that shrimp fed the diets FM15, FM10 and FM5 had poor growth performance and feed utilization compared with shrimp fed the control diet. No difference was observed in feed intake, survival and body composition among dietary treatments. The plasma total cholesterol level of shrimp and the digestibility of dry matter, protein and energy contained in the diets decreased significantly with increasing PM and SBM inclusion levels. Results of this study suggested that fish meal can be reduced from 300 to 200 g kg^?1 when replaced by a mixture of SBM and PM.     

Using Bacillus subtilis E20‐fermented soybean meal as replacement for fish meal in the diet of orange‐spotted grouper (Epinephelus coioides,Hamilton)

The potential of Bacillus subtilis E20‐fermented soybean meal (FSBM) as a partial alternative component of fish meal (FM) in fed diets of orange‐spotted grouper (Epinephelus coioides) was evaluated in this study. An FM‐based diet and seven diets containing 10%, 20% and 30% and 10%, 20%, 30% and 40% of FM replaced by soybean meal (SBM) and FSBM, respectively, were fed to grouper for 84 days to evaluate possible substitution levels of FM by tracking growth performance, digestive enzyme activity and morphological changes in the liver and distal intestine. No significant differences in survival and muscle composition of grouper were found between controls and treatments. Growth performance and feed efficiency of fish fed diets with FM replaced by FSBM up to 30% were not significantly different from controls, whereas significantly decreased growth performance and feed efficiency occurred with diets containing >20% of SBM. Based on the feed efficiency, the maximum substituted levels of FM by SBM and FSBM in grouper diets were 18.36% and 29.32%, respectively, based on broken‐line analyses. Histopathological changes in the liver and distal intestine, and significantly lower activity levels of digestive enzymes, including pepsin in the stomach and trypsin, chymotrypsin, amylase and lipase in the distal intestine, were found in fish fed a diet containing 30% of FM replaced by SBM. However, these parameters were improved by the substitution of FSBM. It is therefore believed that FSBM has great potential to be used as a protein source in grouper diets in partial replacement of FM.     

Postprandial kinetics of gene expression of proteins involved in the digestive process in rainbow trout (<Emphasis Type="Italic">O. mykiss</Emphasis>) and impact of diet composition

The impact of increased incorporation of plant ingredients on diets for rainbow trout was evaluated in terms of gene expression of gastric (gastric lipase, pepsinogen) and intestinal (prolidase, maltase, phospholipase A2) digestive enzymes and nutrient transporters (peptide and glucose transporters), as well as of postprandial levels of plasma glucose, triglycerides and total free amino acids. For that purpose, trout alevins were fed from the start of exogenous feeding one of three different experimental diets: a diet rich in fish meal and fish oil (FM–FO), a plant-based diet (noFM–noFO) totally free from fish meal and fish oil, but containing plant ingredients and a Mixed diet (Mixed) intermediate between the FM–FO and noFM–noFO diets. After 16 months of rearing, all fish were left unfed for 72 h and then given a single meal to satiation. Blood, stomach and anterior intestine were sampled before the meal and at 2, 6 and 12 h after this meal. The postprandial kinetics of gene expression of gastric and intestinal digestive enzymes and nutrient transporters were then followed in trout fed the FM–FO diet. The postprandial profiles showed that the expression of almost all genes studied was stimulated by the presence of nutrients in the digestive tract of trout, but the timing (appearance of peaks) varied between genes. Based on these data, we have focused on the molecular response to dietary factors in the stomach and the intestine at 6 and 12 h after feeding, respectively. The reduction in FM and FO levels of dietary incorporation induced a significant decrease in the gene expression of gastric lipase, GLUT2 and PEPT1. The plasma glucose and triglycerides levels were also reduced in trout fed the noFM–noFO diet. Consequently, the present study suggests a decrease in digestive capacities in trout fed a diet rich in plant ingredients.     

Influence of dietary soy protein and peptide products on bile acid status and distal intestinal morphology of rainbow trout Oncorhynchus mykiss

To investigate the influence of dietary soy protein size on the bile acid status and the distal intestinal morphology in rainbow trout Oncorhynchus mykiss, diets based on soybean meal (SBM), soy protein isolate (SPI) and 4 soy peptide products having different molecular sizes were fed to trout (initial BW, 19?g) for 10?weeks. A diet based on fish meal (Cont) and a diet including the smallest-peptide and low-saponin product (Hi-Nute AM) and supplemented with soya saponin (AMS) were also fed. In fish fed diets SBM and SPI, the gallbladder was atrophied, the proportion of biliary cholyltaurine decreased, and highly vacuolated epithelial cells of mucosal folds and proliferation of connective tissues in the submucosa of the distal intestine were observed. These parameters tended to improve in fish fed soy peptide diets and especially those of fish fed diet AM were similar to fish fed diet Cont. Although the gallbladder of fish fed diet AMS was smaller than fish fed the unsupplemented diet AM, no morphological abnormalities were observed in the distal intestine. These results suggest that soy proteins/peptides with relatively large sizes and with soya saponin affect the bile acid status and distal intestinal morphology of rainbow trout.     

Histomorphology of gastrointestinal tract in bullfrog Rana (Lithobates) catesbeiana and evaluation of the changes induced by a soybean meal‐based diet

Two studies were carried out to (a) characterize the gastrointestinal (GI) tract of bullfrog Rana (Lithobates) catesbeiana and (b) to evaluate the effects of total replacement of fish meal (FM) with soybean meal (SBM) on GI tract health. For characterization of the GI tract, oesophagus, stomach and intestine sections were sampled from 20 bullfrogs (80 g) fed a FM‐based diet. The results revealed that the GI tract of bullfrog is consisted of four tissue layers including mucosa, submucosa, muscularis and serosa, and that the intestine could be divided into duodenum, jejunum, ileum and rectum. Furthermore, the abundance and length of mucosal folds suggested that jejunum is the primary site of digestion and absorption of nutrients. In the second study, a diet containing 44% fish meal (FM) was formulated and used as a FM‐based diet, and a SBM‐based diet was prepared by entire substitution of FM with SBM. Sixty bullfrogs (35 ± 1 g) were divided into three replicates of the two groups and were fed the test diets to apparent satiation twice daily for 8 weeks. The changes in pH and morphology of GI tract in response to the shift in dietary protein source were evaluated. The results showed the enhancement of pH values in GI tract of the SBM group excluding cardia, jejunum and rectum. Also, SBM diet triggered significant decreases in the number, height and width of mucosal folds, while an opposite trend was observed for thickness of lamina propria. Moreover, the entire replacement of FM with SBM led to the separation of submucosa from muscularis and incidence of lesion in mucous epithelium. The findings in this study showed that jejunum is the main site of nutrients digestion and absorption. Also, it was demonstrated that entire replacement of FM with SBM adversely influenced the GI tract health in bullfrog.     

四种植物蛋白对黄颡鱼肠道形态结构的影响

以鱼粉为对照,研究了饲料中分别添加25%和50%的豆粕、花生粕、菜粕和棉粕这4种植物蛋白时黄颡鱼(Pelteobagrus fulvidraco)肠道形态结构的变化。试验鱼初始体重为(22.95±0.35)g,饲养8周。结果表明:与对照组比,植物蛋白添加水平在25%时,豆粕组黄颡鱼的肠道组织结构没有明显变化;花生粕组肠黏膜上皮细胞之间界限不清晰,空泡较多。黏膜下层有所增厚,但未见淋巴细胞浸润。菜粕组和棉粕组肠道黏膜高度均显著下降,且棉粕组黏膜下层增厚,上皮内有淋巴细胞浸润,肌层也显著变薄。添加水平达到50%时,各试验组黄颡鱼中肠结构均产生明显变化。从蛋白质效率看,50%的豆粕组和棉籽粕组与对照组没有显著差异,而50%花生粕组和菜粕组与对照组差异显著。上述结果表明:黄颡鱼肠道对饲料植物蛋白种类和添加量很敏感,4种植物蛋白选用时,豆粕和棉粕要优于花生粕和菜粕,花生粕、棉粕、菜粕的安全添加量应在25%以下,豆粕应在50%以下,适宜添加量有待深入研究。     

Galactooligosaccharide and a combination of yeast and β-glucan supplements enhance growth and improve intestinal condition in striped catfish <Emphasis Type="Italic">Pangasianodon hypophthalmus</Emphasis> fed soybean meal diets

The effects of galactooligosaccharide (GOS) and a combination of yeast and β-glucan (YβG) supplementation of dietary soybean meal (SBM) on the growth and digestive performance of striped catfish Pangasianodon hypophthalmus were evaluated. Four isonitrogenous (30% protein) and isocaloric (19 MJ/kg diet) diets were formulated to contain 100% fish meal (FM) protein, 55% FM protein/45% SBM protein, FM-SBM supplemented with 1% GOS, and a combination of 1% yeast and 0.1% β-glucan, respectively. Each diet was fed for 12 weeks to three groups of 30 striped catfish fingerlings (average weight 16.45?±?0.07 g) maintained in circular fiberglass tanks (600 l). Growth, feed utilization, and muscle protein composition of fish improved significantly after supplementation with either GOS or YβG compared to the unsupplemented SBM diet, but were similar to those of fish fed the FM diet. Nutrient digestibility, digestive enzyme activities, villi and microvilli length were significantly increased in fish fed the supplemented SBM diets. The gut microbiota ranking profile showed that supplementing the SBM diet with YβG and GOS gave a ranking of Verrucomicrobia, Spirochaetes, Bacteriodetes, and Actinobacteria phyla similar to that of the FM diet. Thus, diet containing 45% protein from soybean supplemented with either GOS or YβG can be recommended to improve the growth and digestive performance of striped catfish.     

Growth and intestinal morphology in cobia (Rachycentron canadum) fed extruded diets with two types of soybean meal partly replacing fish meal

Juvenile cobias, Rachycentron canadum, were fed extruded diets containing toasted defatted soybean meal (SBM) or untoasted defatted SBM [white flakes (WF)] to study growth and feed conversion, and to study if SBM induces morphological changes in the gastrointestinal (GI) tract. Three diets were produced: a fish meal‐based control diet (FM diet) with 558 g FM kg^?1, and two diets with 335 g FM and either 285 g SBM kg^?1 (SBM diet) or 285 g WF kg^?1 (WF diet). The diets were extruded at approximately 120°C with 280 g kg^?1 moisture. Triplicate groups of cobias (mean weight: 25.9 g) were fed the diets during 6 weeks. Feed intake of the FM and SBM diets were not significantly different, whereas the cumulative feed intake of cobias fed the WF diet was lower (P < 0.05) than that of cobias fed the FM and SBM diets after the first 21‐day period. Specific growth rate and feed conversion ratio were not significantly different between cobias fed the FM and SBM diets, but significantly poorer results were obtained in cobias fed the WF diet. No morphological differences in the GI tract could be attributed to the diets, and cobias fed soy did not develop enteritis in the distal intestine.     

Effects of fructooligosaccharide on growth,immunity and intestinal microbiota of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

The effects of fructooligosaccharide (FOS) on growth performance, immunity and predominant autochthonous intestinal microbiota of shrimp (Litopenaeus vannamei) fed diets with fish meal (FM) partially replaced by soybean meal (SBM) were evaluated. After acclimation, shrimps (1.82 ± 0.01 g/kg) were allocated into 15 tanks (25 shrimps per tank) and fed five different diets including positive control diet (C0, containing 250 g/kg FM and 285 g/kg SBM), control diet (C, containing 125 g/kg FM, 439 g/kg SBM) and three experimental diets supplemented with 1.0 g/kg FOS (T1), 2.0 g/kg FOS (T2) and 4.0 g/kg FOS (T3) to control diet (C) respectively. Shrimps were fed diets to apparent satiation three times per day, and 15 shrimps from each aquarium were randomly sampled and analysed at the end of the 6‐week feeding trial. The results showed that FBW, WGR, SGR and SR decreased, while FCR and FI increased significantly in control (C) compared with positive control (C0). Besides, significantly decreased trypsase and lipase activities, and SOD, AKP and ACP activities were recorded in control (C) compared with positive control (C0). On the other hand, significantly improved SGR and decreased FCR were observed in groups T1, T2 and T3 compared with control (C). Moreover, lipase and amylase activities enhanced significantly in group T3 compared with the control (C), while GOT and GPT activities dropped significantly with the increment supplementation of FOS in diets. Compared with the control (C), SOD activity enhanced significantly and MDA level decreased significantly in groups T2 and T3, and improved AKP and ACP activities were observed in group T3. In addition, dietary FOS improved the microbial diversity, and suppressed several potential pathogens, such as Vibrio tubiashii, Vibrio parahaemolyticus and Photobacterium damselae‐like strains in the intestine of shrimp. Overall, these results proved FOS could relieve the side effects induced by SBM and supported the use of 2.0–4.0 g/kg FOS in shrimp diets with FM partially replaced by SBM.     

Optimization of the supplemental essential amino acids to a fish meal-free diet based on fermented soybean meal for rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

To minimize the supplemental essential amino acids (EAAs) to a fish meal-free diet for rainbow trout Oncorhynchus mykiss, four types of fish meal-free diets and a control fish meal-based diet were fed to triplicate groups of trout (initial BW, 16 g) for 10 weeks. Two fish meal-free diets based on a fermented and an unfermented soybean meal were unsupplemented with EAAs (diet FSBM and SBM), and two fish meal-free diets based on the fermented soybean meal were supplemented with a combination of lysine and methionine (diet F + ML) and all EAAs (diet F + All), the EAA contents of which were lower than those of the control diet (diet FM). Although physiological conditions such as the biliary bile acid status and morphological features of fish fed diet FSBM were improved and similar to those of fish fed diet FM, the growth performance was not significantly different (P > 0.05) from fish fed diet SBM. The growth performances and whole body protein contents of fish fed F + ML and F + All diets were similarly improved compared to fish fed diet FSBM. These findings indicate that supplementation of lysine and methionine to a fermented soybean meal-based fish meal-free diet is enough to maximize the amino acid utilization of the diet.