Dietary saponins and phytosterols do not affect growth,intestinal morphology and immune response of on‐growing European sea bass (Dicentrarchus labrax)

This study was the first to investigate the effect of soy antinutrients, saponins and phytosterols, in on‐growing sea bass. Seven diets were formulated: a control diet (fishmeal and fish oil based) and six diets containing 1 or 2 g kg^?1 levels of soya saponins, 5 or 10 g kg^?1 levels of phytosterols or a combination of 1 g kg^?1 saponins + 5 g kg^?1 phytosterols or 2 g kg^?1 saponins + 10 g kg^?1 phytosterols. After a 59 days feeding trial fish were weighed, faeces collected for digestibility studies and plasma sampled for cholesterol quantification. At day 15 and 59, distal intestine (DI) samples were collected for histological evaluation and quantification of maltase (Malt), alkaline phosphatase (AlP) and leucine aminopeptidase (LAP) activities. At day 59, DI was collected for gene expression of AlP, Malt and immune related genes. Antinutrients had no effect on fish performance, digestibility, plasma cholesterol levels and digestive enzymes activities and gene expression. Only mild morphological changes were present in groups fed high levels of saponins + phytosterols. Expression of immune related genes showed no differences between groups. Overall, on‐growing sea bass showed high tolerance to dietary antinutrients up to the levels tested.     

Digestive function and intestinal integrity in Atlantic salmon (Salmo salar) fed kernel meals and protein concentrates made from yellow or narrow-leafed lupins

This study assessed the effects of yellow lupin (Lupinus luteus) and narrow-leafed lupin (L. angustifolius) kernel meals and protein concentrates on the gastrointestinal integrity, capacity for digestive hydrolysis, and digestibility of nutrients in Atlantic salmon. A basal diet (FM) was made from fish meal, wheat, and fish oil. Six additional diets were formulated by replacing 30% of the FM diet with lupin kernel meal made from L. l. cv. Wodjil (LKM), L. a. cv. Belara (BKM), and L. a. cv. Myallie (MKM), lupin protein concentrates made from the same L. l. (LPC) and L. a. cv. M (MPC), or extracted soybean meal (SBM). All diets were extruded. Each diet was fed to three groups of 176 g salmon kept in 1 m² tanks with 5.6 °C saltwater for 3 weeks prior to sampling of blood, intestinal organs, digesta, and faeces. Inclusion of lupin meals in the diets resulted in harder and more condensed feed particles. Ulcer-like lesions were observed in the stomach of fish from all feeding groups, and this was worsened by lupin in the diet, but did not appear to be pellet hardness related. No consistent altered morphology was observed in the distal intestine (DI) of fish fed the FM and lupin diets, while the DI of fish fed SBM showed consistent and typical soybean meal-induced pathomorphological changes. Plasma cholesterol was higher when feeding MKM and LKM than when feeding FM, MPC, and LPC, with intermediate levels when feeding BKM and SBM. Feeding LKM and LPC resulted in a higher weight of the GIT when related to body weight. Trypsin activity and bile acid concentration were generally higher in digesta from the pyloric (PI) and mid (MI) intestine when feeding FM and lupin diets than when feeding SBM, while the opposite was seen for trypsin activity in digesta from DI. There were no effects of diet on leucine aminopeptidase (LAP) and maltase activity in PI and MI, but in DI the activity of these brush border enzymes were significantly lowered when feeding SBM. SBM in the diet resulted in watery faeces and lowered apparent digestibility of lipid, but this was not observed when feeding the lupin diets. To conclude, the tested lupin kernel meals and protein concentrates did not alter the intestinal function in Atlantic salmon when included at 30% of the diet. Dietary lupin was, however, involved in the worsening of ulcer-like gastric lesions.     

Evaluation of the effect of commercially available plant and animal protein sources in diets for Atlantic salmon (Salmo salar L.): digestive and metabolic investigations

The present study investigated the effect of various alternative diet ingredients partially replacing fishmeal (FM) on digestive and metabolic parameters in Atlantic salmon (Salmo salar L.) post-smolts (initial body mass 305 ± 69 g) following 12 weeks of feeding. Experimental diets containing 20 % extracted sunflower (ESF), pea protein concentrate (PPC), soy protein concentrate (SPC), feather meal (FeM) and poultry by-product (PBY) were compared to a reference diet containing FM as the main protein source. For the different intestinal compartments trypsin, lipase, bile salts, dry matter and chyme-associated leucine aminopeptidase (LAP) were measured from the content and LAP was measured in the tissue. Selected metabolites were measured in plasma samples. In general, use of plant proteins resulted in low C-LAP activity, low plasma cholesterol and high plasma magnesium. The plasma levels of cholesterol and Mg reflecting were most likely reflections of the composition of the diet, while the LAP activity in chyme may indicate lower epithelial cell turnover. Other responses varied depending on the plant protein source. Results from the animal protein substitution also varied both between diets and compartments; however, both materials increased lipase activity in DI. FeM resulted in a significant increase in both total and specific LAP activities suggesting an attempt to increase the digestive capacity in response to low digestibility of the diet while PBY showed very little difference from the FM-fed control fish. The present trial indicates that 20 % PPC, SPC and PBY can partially replace FM in diets for Atlantic salmon. The qualities of ESF and FeM used in this trial show little promise as FM replacement at 20 % inclusion level.     

饲料中添加大豆皂甙对大菱鲆幼鱼生长和肠道健康的影响

为研究大豆皂甙对大菱鲆幼鱼生长性能、消化酶活性、肠道组织结构完整性和肠道菌群结构的影响,在以鱼粉为蛋白源的基础饲料中分别添加0%和0.3%的大豆皂甙,配制成鱼粉组和大豆皂甙组2种等氮等脂的实验饲料来投喂体质量为(4.63±0.01) g的大菱鲆进行12周的摄食生长实验。结果显示,饲料中添加0.3%的大豆皂甙对大菱鲆的生长性能没有产生显著影响,但显著降低了胃蛋白酶及肠淀粉酶活性;2组实验中大菱鲆肠道组织形态无明显差异,但大豆皂甙组肠道紧密连接蛋白的基因表达量显著降低。肠道菌群分析结果显示,大菱鲆肠道中相对丰度最高的门和属分别为变形菌门和盐单胞菌属。LEfSe和MetaStat分析显示,饲料中添加大豆皂甙后显著提高了大菱鲆肠道内优势菌(变形菌门及希瓦氏菌属),皂甙水解相关的肠道微生物(鞘脂单胞菌属、普氏菌属、栖瘤胃普雷沃菌以及普通拟杆菌)及潜在致病菌(莫氏杆菌属和发光杆菌属)的相对丰度,同时显著降低了Caenimonas、Niastella和条件致病菌罗尔斯通菌属的相对丰度。研究表明,0.3%大豆皂甙抑制了大菱鲆消化酶活性及肠道紧密连接蛋白的基因表达,且引起了大菱鲆肠道菌群结构的显著改变。因此,大豆皂甙对鱼类肠道健康尤其是肠道菌群的影响不容忽视,值得进一步研究。     

Sterol requirement of juvenile lobsters, Homarus sp.

Juvenile lobsters were fed purified or unrefined diets in which the qualitative and quantitative sterol composition varied. Dietary cholesterol was required. A level of dietary cholesterol as low as 0.12% (dry weight) in a purified diet was satisfactory for normal growth and survival. No significant increases in growth were observed when lobsters were fed unrefined diets with cholesterol levels ranging from 0.19 to 0.59% (dry weight). Total cholesterol content of the whole body tissue lipid ranged from 0.012 to 0.046% (wet weight), lowest values being characteristically associated with those animals fed purified diets virtually devoid of cholesterol. Serum sterol levels were similar except for reduced levels associated with the sterol-free diet.Total replacement of cholesterol with a mixture of phytosterols composed primarily of β-sitosterol did not yield good growth and survival. Phytosterols composed large proportions of the total body sterols of those lobsters fed diets containing phytosterols exclusively. At least a portion and possibly all of the sterol requirement of juvenile lobsters is specific for cholesterol.     

Effects of graded levels of standard soybean meal on intestinal structure, mucosal enzyme activities, and pancreatic response in Atlantic salmon (Salmo salar L.)

Duplicate tanks of c.280 g Atlantic salmon (Salmo salar L.) were fed for 60 days on diets in which fishmeal was substituted with graded levels of extracted soybean meal (SBM) comprising 0%, 10%, 15%, 20%, 25% or 35% of total protein. The effects on feed intake, growth, feed conversion, apparent digestibility and utilization of macronutrients and energy, pathohistological response of the distal intestine (DI), activities of digestive enzymes in the mid and distal intestinal mucosa, and faecal trypsin and plasma insulin concentrations were studied. A negative, dose‐dependent effect of SBM was observed on nearly all performance parameters with a notable exception of feed intake. The lowest SBM inclusion level of 10% resulted in moderate pathohistological changes in the DI. Each subsequent increase in SBM level increased the number of fish displaying severe changes. In contrast to the mid‐intestine (MI), all enzyme activities in the distal intestinal mucosa decreased dose‐dependently with increasing SBM inclusion. Faecal trypsin increased up to an SBM inclusion level of 20% and then levelled off. Plasma insulin increased from 0% to 15% SBM inclusion and then decreased. The results suggest that caution should be exercised in the use of even low levels of extracted SBM in salmon feeds.     

Feeding Atlantic salmon Salmo salar L. soybean products: effects on disease resistance (furunculosis), and lysozyme and IgM levels in the intestinal mucosa

Two trials were initiated to investigate the consequences of including various soybean products in diets for Atlantic salmon Salmo salar L. on (1) mortality following infection by Aeromonas salmonicida ssp. salmonicida during a cohabitation challenge, and (2) the lysozyme and IgM content of the intestinal mucosa. Groups of salmon were fed control diets containing fishmeal as the sole protein source (Contr1 and Contr2, respectively), soy concentrate-containing diets (SoyConc1 and SoyConc2, respectively), or diets containing either solvent-extracted soybean meal (SoyMeal, trial 1) or soybean molasses (SoyMol, trial 2), an alcohol extract of soybean meal. Both SoyMeal and SoyMol caused enteritis-like changes in the distal intestine, which were not observed in fish fed the Contr1, Contr2, SoyConc1, or SoyConc2 diets. There were significant differences ( P  < 0.05) in mortality between feeding groups following the A.s. salmonicida challenge: these differences were greatest in fish fed SoyMeal (65.6%), least in fish fed SoyConc1 (60.5%), and intermediate in the fish fed the Contr1 diet (62.9%). The SoyMol diet caused significantly ( P  < 0.0001) increased levels of both lysozyme and IgM in the mid and distal intestinal mucosa. It is concluded that components of soybean meal and soybean molasses cause an inflammatory response in the distal intestine that may lead to increased susceptibility to furunculosis.     

Alcohol-soluble components in soybeans cause morphological changes in the distal intestine of Atlantic salmon, Salmo salar L.

Standard soybean meal, heat treated to differing degrees and containing varying levels of soybean lectin and trypsin inhibitor, was used to study the effect of soybean-containing diets on the morphology of the distal intestine in Atlantic salmon, Salmo salar L. A reference diet based on fish meal and a fish meal diet mixed with an alcohol extract of soybean meal were used. The fish (145 g) were kept in 27 m³ net pens (200 fish per pen) in sea water with an average temperature of 11 °C for 12 weeks. Whereas a normal morphology of the distal intestine was seen in the fish fed the reference diet, all soybean diets caused alterations in the distal intestine irrespective of heat treatment. Similar changes were observed with the diet which had added alcohol solubles. It is concluded that alcohol-soluble components in the soybeans are responsible for the observed changes. It cannot be determined which of the soybean antinutrients is causing the alterations from the present study. Oligosaccharides and saponines are possible candidates. However, the possibility that unknown antinutrients are affecting the salmon intestine should not be overlooked.     

Effects of diet supplementation of soya‐saponins,isoflavones and phytosterols on Atlantic salmon (Salmo salar,L) fry fed from start‐feeding

A 14‐week trial was conducted to investigate the effects of antinutritional factors (ANFs) commonly present in soybean ingredients, singly and in combination, on Atlantic salmon (Salmo salar L.) fed from start‐feeding. The experimental diets consisted of a negative control fish meal diet (FM), and a positive control diet with 167 g kg^?1 soybean meal inclusion (SBM) and four diets based on the FM diet supplemented with 2 g kg^?1 soya‐saponins (SAP), 1.5 g kg^?1 isoflavones (IFL), 0.3 g kg^?1 phytosterols (PHS) or a mixture of these (MIX). Fish fed the SAP diet showed significantly higher growth performance than those fed FM, while the IFL treatment significantly decreased growth performance of salmon fry. Fish fed the IFL diet had significantly lower maltase activity and higher trypsin activity in proximal intestine than fish fed the FM diet. Histological differences were observed in the liver of fish fed the IFL diet, characterized by reduced size of the hepatocytes. Fish fed the PHS and IFL diets showed the highest frequencies of skeletal deformities among the six treatments. In conclusion, the results indicate that purified isoflavones may negatively affect growth performance, intestinal function, liver metabolism and bone formation of salmon fry.     

Effects of dietary cholesterol supplementation on growth and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed diets with cottonseed meal or rapeseed meal

This study was conducted to evaluate the effects of cholesterol on growth and cholesterol metabolism of rainbow trout (Oncorhynchus mykiss) fed diets with cottonseed meal (CSM) or rapeseed meal (RSM). Four experimental diets were formulated to contain 550 g kg^?1 CSM or 450 g kg^?1 RSM with or without 9 g kg^?1 supplemental cholesterol. Growth rate and feed utilization efficiency of fish fed diets with 450 g kg^?1 RSM were inferior to fish fed diets with 550 g kg^?1 CSM regardless of cholesterol level. Dietary cholesterol supplementation increased the growth rate of fish fed diets with RSM, and growth rate and feed utilization efficiency of fish fed diets with CSM. Similarly, dietary cholesterol supplementation increased the plasma total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triiodothyronine levels, but decreased the plasma triglycerides and cortisol levels of fish fed diets with RSM or CSM. In addition, supplemental cholesterol increased the free cholesterol and TC levels in intestinal contents, but decreased the hepatic 3-hydroxy-3-methyl-glutaryl-CoA reductase activity of fish fed diets with RSM or CSM. These results indicate that 9 g kg^?1 cholesterol supplementation seems to improve the growth of rainbow trout fed diets with CSM or RSM, and the growth-promoting action may be related to the alleviation of the negative effects caused by antinutritional factors and/or make up for the deficiency of endogenous cholesterol in rainbow trout.     

Effects of diet composition on apparent nutrient absorption along the intestinal tract and of subsequent fasting on mucosal disaccharidase activities and plasma nutrient concentration in Atlantic salmon Salmo salar L.

Atlantic salmon (1.9 kg), were fed a low carbohydrate/high protein or a high carbohydrate/low protein diet for 20 days prior to a fasting period of 60 days. At the end of the feeding period chyme was collected from the gastro-intestinal tract divided into six sections, for studies of starch, lipid and amino acid absorption. Blood and gut wall samples were taken on days 0, 5, 12, 33 and 60 of fasting. The results showed that 50% or more of amino acid, lipid and starch absorption took place in the pyloric region. The distal intestine was also of quantitative importance for lipid absorption. Diet composition affected only starch absorption. The effect was apparent in the pyloric region with no compensatory absorption in the more distal regions. Brush-border disaccharidase activities were negligible in the stomach, high in mid-intestinal regions and decreased towards the distal regions. High carbohydrate diet caused reduced trehalase activity. Fasting caused immediate decreases in disaccharidase activities as well as in plasma glucose, triacylglycerols, cholesterol and insulin. During the second week of the fasting period, temporary increases were seen in mucosal maltase, sucrase and trehalase activities and in plasma insulin level. Similar changes were observed for several plasma amino acids. To regain efficient nutrient digestion after a fasting period, a restoration period may therefore be needed.     

Xylanase supplementation in plant protein‐enriched diets improves growth performance by optimizing the intestinal microflora and enhancing the intestinal immune function in grass carp grow‐out (Ctenopharyngodon idella)

This study investigated the effect of xylanase supplementation of a plant protein‐enriched diet on the growth performance and intestinal immune function of grass carp grow‐out (Ctenopharyngodon idella). Five hundred forty healthy grass carp grow‐out (232.74 ± 0.12 g) were fed diets containing graded levels of xylanase for 60 days. The fish were then challenged with Aeromonas hydrophila for 14 days. The results indicated that xylanase supplementation (a) improved fish growth performance and optimized the intestinal microflora; (b) increased lysozyme and acid phosphatase activities, complement and immunoglobulin M levels and antibacterial peptide hepcidin mRNA levels, thereby enhancing fish intestinal immune function; and (c) attenuated intestinal inflammation associated with the inhibition of the NF‐κB signalling pathway and activation of the TOR signalling pathway, resulting in the down‐regulation of pro‐inflammatory cytokines [except IL‐1β and IL‐12p40 in the distal intestine (DI) and IL‐6 in the proximal intestine (PI)] and up‐regulation of anti‐inflammatory cytokines [except IL‐4/13B and TGF‐β1 in the mid intestine (MI) and DI]. Finally, on the premise of a basal diet containing 45.8 g/kg araboxylans (AXs), the appropriate supplementation levels based on the ability to improve per cent weight gain (PWG) and prevent enteritis were estimated to be 1,527 and 1,608 U/kg, respectively.     

Capacity for digestive hydrolysis and amino acid absorption in Atlantic salmon (Salmo salar) fed diets with soybean meal or inulin with or without addition of antibiotics

This experiment was done to study the effects of dietary soybean meal (SBM) and inulin (a prebiotic) on the capacity for digestive hydrolysis and amino acid absorption by Atlantic salmon, and how a dietary supplement of the broad-spectrum antibiotic oxytetracycline (OTC) modulated these responses. A control diet (FM) was made from fish meal, fish oil and extruded wheat. Two similar diets were made with 250 g soybean meal (SBM) or 75 g inulin kg^− 1. Each diet was made with or without a supplement of 3 g OTC kg^− 1. All six diets contained yttrium oxide for estimation of apparent nutrient absorption. Each diet was fed to two groups of 172 g salmon kept in 1 m² tanks with 9 °C saltwater for 3 weeks. Intestinal organs were then sampled and weighed. Gastrointestinal tracts (GIT) were sectioned for analyses of brush border alkaline phosphatase (ALP) and leucine aminopeptidase (LAP) activities. Tissue from the distal intestine (DI) was also fixed for histological examination. Digesta from the different sections were freeze dried for estimation of trypsin and amylase activities, and of apparent absorption of amino acids (AA), nitrogen (N), and sulphur (S). About 85% of the trypsin activity, 70% of the amylase activity, 85% of the ALP activity, and 82% of the LAP activity were found in the proximal (PI) and mid (MI) intestine of fish with functional DI, and the absorption of AA, N, and S was quantitatively completed in the MI. Dietary OTC resulted in lower relative liver weight, but apart from increased ALP and LAP activities in DI when feeding OTC in combination with inulin, OTC did not modify the responses to dietary SBM or inulin. Dietary SBM resulted in lower relative liver weight, and induced pathomorphological changes in the DI mucosa, thus lower the ALP and LAP activities in the DI. SBM also stimulated absorption of AA, N, and S in the PI, but at the same time increased the activities of trypsin and amylase in the DI, indicating reduced re-absorption and increased faecal losses of these endogenous enzymes. Dietary inulin did not damage the DI, and stimulated intestinal growth and higher relative mass of the GIT. Inulin without OTC did not affect the hydrolytic and absorptive capacity of the salmon GIT.     

Dietary lipid level affects fatty acid composition and hydrolase activities of intestinal brush border membrane in seabass

Triplicate groups of juvenile seabass (initial weight of 241 g) were fed during 13 weeks three isonitrogenous experimental diets containing different lipid levels, 12% (LL group), 21% (ML group) and 30% (HL group). At the end of the experiment, fish weight gain was similar among the 3 dietary groups. Intestinal brush border membranes were purified for each dietary group; one part of the brush border fraction was dedicated to enzyme assays, the remaining fraction being used for lipid extraction followed by fatty acid analysis. The fatty acid composition of the brush border membrane differed among the 3 groups, although the 3 experimental diets had the same fatty acid composition. The increase in dietary lipid level resulted in a lowering in (n-3) polyunsaturated fatty acid (PUFA) paralleled with an increase in monounsaturated fatty acid. A significant reduction in the brush border enzyme activities, namely alkaline phosphatase, aminopeptidase N, -glutamyl transpeptidase and maltase, was also observed with the elevation of the dietary lipid level. The change in activity of intestinal digestive enzymes, which are membrane-bound proteins, could be attributed to the modification of fatty acid composition and fluidity of the brush border membranes (BBM). Such lowering in PUFA and increase in monounsaturated fatty acid in BBM, concomitant with a decline in membrane enzymatic activity, has been described as a malnutrition indicator in mammals. It raises the question of possible disorders of gut functions in fish fed increasing lipid levels.     

Effects of Neutral Phytase Supplementation on Biochemical Parameters in Grass Carp,Ctenopharyngodon idellus,and Gibel Carp,Carassius auratus gibelio,Fed Different Levels of Monocalcium Phosphate

Two 8‐wk studies were conducted to evaluate the effects of neutral phytase supplementation on hemato‐biochemical status, liver biochemical parameter, and intestinal digestive enzyme activity of grass carp, Ctenopharyngodon idellus, and gibel carp, Carassius auratus gibelio, fed with different levels of monocalcium phosphate (MCP). The control diet was prepared with 2% MCP but without phytase (P2.0). The other three experimental diets were prepared with the addition of 1.5, 1.0, and 0.5% MCP, respectively, when supplemented with 500 U/kg neutral phytase in each diet and designated as PP1.5, PP1.0, and PP0.5, respectively. The results indicated that the serum alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase (AST) activities, as well as the albumin (ALB) content were increased in grass carp (P < 0.05) and gibel carp (P > 0.05) fed with phytase‐supplemented diets. Meanwhile, the serum cholesterol, high‐density lipoprotein, and total protein contents of the two species of fish were increased in comparison to the control. In addition, dietary phytase inclusion did not significantly affect hepatic ALP, ALT, and AST activities in the two species of carp fed with different levels of MCP. Amylase activity increased in foregut and hindgut of both species when fed with the phytase‐supplemented diets while lipase activity was reduced in the foregut and hindgut in both fish. This study suggests that neutral phytase supplementation increases serum ALP, ALT, and AST activities but does not notably affect these enzyme activities in the liver of the two species of carp when fed different levels of MCP. On the other hand, amylase activity increased while lipase activity was reduced in the intestine of the species of carp fed with phytase‐supplemented diets.     

Digestive capacity, intestinal morphology, and microflora of 1-year and 2-year old Atlantic cod (Gadus morhua) fed standard or bioprocessed soybean meal

The objectives of this work were to evaluate how dietary soybean meal (SBM) or a soy meal made by bioprocessing the SBM (BPSBM) to remove anti-nutritional factors affected hydrolytic capacity, amino acid absorption, intestinal morphology, and microflora along the intestinal tract of Atlantic cod at two life stages. Three fish meal based standard cod diets were formulated to contain no soy (FM control), 25% SBM, or 22% BPSBM. Prior to sampling the diets were fed to duplicate groups of 0.5 kg (1-year old) and 1.7 kg (2-year old) cod for a period of 3 months, and the groups reached 0.9 and 2.5 kg, respectively. Digesta was then sampled from different intestinal sections for analyses of trypsin and amylase activity as well as absorption of amino acids, nitrogen, and sulphur. Gastrointestinal sections were sampled for measurements of relative weight (kg^− 1 body weight), and tissues from these sections were sampled for analyses of brush border enzyme (alkaline phosphatase (ALP), leucine aminopeptidase (LAP), and maltase) activity and histological examination. Microflora was sampled from both digesta and the intestinal wall. The SBM diet stimulated relative growth of all gastrointestinal sections except the distal intestine in both age classes. Relative growth of the pyloric intestine was also stimulated by BPSBM. The pyloric caeca and the upper mid intestine were found to be the major sites for enzymatic hydrolysis of protein and starch and for amino acid absorption. Dietary SBM and BPSBM did not alter the activity of trypsin and LAP, but the activity of these enzymes in the proximal intestine was affected by age, being higher in 1-year old than in 2-year old cod. The rate of amino acid, nitrogen, and sulphur absorption along the gastrointestinal tract was not affected by SBM, but was slowed by BPSBM. Dietary SBM or BPSBM did not alter the morphology of the intestinal mucosa in any sections of the cod intestine. The distal-most structure of the intestine, a compartment with inlet and outlet (anus) valves, showed very high microbial colonisation in the mucosal brush border. Inclusion of SBM in the diet changed the intestinal microflora, increasing the population level of transient bacteria in the pyloric and mid intestine, but reducing the population level of adherent bacteria throughout the intestine. To conclude, Atlantic cod appeared to have a robust and flexible digestive system able to adjust to high dietary levels of soy protein meals.     

Supplemental effect of bile salts to soybean meal-based diet on growth and feed utilization of rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

A feeding experiment was conducted to evaluate the supplemental effect of bile salts to a defatted soybean meal-based non-fish meal diet for rainbow trout Oncorhynchus mykiss. A fish meal-based diet (FM) and two non-fish meal diets with and without bovine bile salts (SC+B and SC, respectively) were fed to fish (13 g initial weight) for 10 weeks. Fish fed diet SC showed inferior growth and feed efficiency, while bile salt supplementation improved the parameters to the same levels as fish fed diet FM. Crude fat and starch digestibility of diet SC-fed fish decreased after the 10-week feeding trial compared to the data obtained with fish that had no experience of the diet. Total biliary bile salt content and intestinal maltase activity of fish fed diet SC were the lowest among treatments, while these parameters were improved by bile salt supplementation. Morphological changes occurred in the distal intestine and liver of the diet SC group, although the histological features of fish fed diet SC+B were similar to those of fish fed diet FM. These results suggest that bile salt supplementation to a soybean meal-based diet improves the nutrient utilization by normalizing digestive processes in rainbow trout.     

不同碳水化合物和蛋白质水平膨化饲料对大规格草鱼生长、肠道消化酶及血清指标的影响

为探究不同碳水化合物和蛋白质水平膨化饲料对大规格草鱼生长、体成分、肠道消化酶和血清指标的影响,以初始体质量(398.6±5.9)g的大规格草鱼为研究对象,设置不同碳水化合物/蛋白质水平分别为C31P30、C34P28、C37P26、C40P24、C43P22、C46P20、C49P18的7组膨化饲料,养殖周期为16周。实验结果显示,各饲料组草鱼成活率(SR)差异不显著,随着蛋白质水平的下降、碳水化合物水平的升高,增重率(WGR)呈下降趋势,蛋白质效率(PER)呈升高趋势;肝体比(HSI)、脏体比(VSI)、肠体比(ISI)、肌肉和肝脏粗脂肪(CF)含量均有随饲料碳水化合物水平升高而升高的趋势。随着饲料中碳水化合物水平升高、蛋白质水平下降,各组间草鱼肌肉粗蛋白质(CP)含量无显著差异;肝糖原、肌糖原含量呈升高趋势,饲料中碳水化合物水平分别高于46%和40%时,肝糖原、肌糖原含量显著升高。肠道胰蛋白酶(PRS)和淀粉酶(AMS)活性随饲料中碳水化合物水平的升高呈先下降后升高趋势,脂肪酶(LPS)活性呈升高趋势;血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL)、高密度脂蛋白(HDL)含量及谷草转氨酶与丙转氨酶(GOT/GPT)比值都随饲料中碳水化合物水平升高和蛋白质水平下降而呈升高的趋势。本实验结果显示:当饲料碳水化合物水平高于37%、蛋白质水平低于26%时,将显著影响草鱼的生长,饲料中高碳水化合物水平将导致鱼体肝体比、脏体比、肠体比以及肌肉和肝脏脂肪含量升高。