Effects Of Dietary Soybean Meal Research Articles

The Effect of Fermented Soybean Meal on The Growth Performance of Kampong Chickens

Abstract The present study evaluated the effect of dietary soybean meal (SBM) fermented with Bacillus subtilis and Aspergillus niger on the performance of kampong chickens measured at eight weeks. Ninety birds at 21 d (210±3.69 gram) were used for the experiment. The birds were randomly separated into three treatment groups consisting of six replicates, with five birds per replicate. The treatments were without steam conditioning and fermentation (P0), where the two other groups were fermented with Bacillus subtilis (P1) and Aspergillus niger (P2). Basal diets were based on corn-soybean with crude protein (CP) of 16% and metabolism energy (ME) of 2800 Kcal. The result showed that dietary SBM fermented with Bacillus subtilis and Aspergillus niger increased average daily gain (ADG), final body weight (BW), and decreased feed conversion when compared to control (P<0.05). In conclusion, the present study suggested that replacing SBM with fermented soybean meal increased performance without negatively affecting the feed intake of kampong chickens.

Corrigendum: Effect of dietary soybean meal on growth performance, apparent digestibility, intestinal digestive enzyme activity and muscle growth-related gene expression of Litopenaeus vannamei

CORRECTION article Front. Mar. Sci., 12 May 2023Sec. Aquatic Physiology Volume 10 - 2023 | https://doi.org/10.3389/fmars.2023.1197207

Effect of dietary soybean meal on growth performance, apparent digestibility, intestinal digestive enzyme activity and muscle growth-related gene expression of Litopenaeus vannamei

Soybean meal is one of the major components of aquatic animal diets, whereas little information is available about the evaluation of soybean meal growth suppression mode of action. A 42-day feeding trial was performed to assess the effects of dietary soybean meal on growth performance, apparent digestibility, intestinal digestive enzyme activity, and muscle growth–related gene expression of Litopenaeus vannamei. A total of 600 shrimp were randomly distributed into 20 tanks with 30 shrimp per tank and four tanks per group. The soybean meal was added to the diets at the rate of 20% (T20), 28% (T28), 35% (T35), 42% (T42), and 50% (T50), respectively. Shrimp were fed with apparent satiation three times daily. Results indicated that the final body weight, weight gain rate, specific growth rate, feed intake, intestinesomatic index, dressed weight percentage, and the apparent digestibility coefficients of dry matter, crude protein, crude lipid, and ash were linearly decreased (p < 0.05), but feed coefficient was linearly increased (p < 0.05) as dietary soybean meal increased from 20% to 50%. The intestinal trypsin and amylase activities were decreased (p < 0.05) as dietary soybean meal increased from 20% to 50%, and reached significance at the level of 35%, 42%, and 50%. Shrimp fed with T20 had higher (p < 0.05) intestinal lipase activity than those fed with other diets. The mRNA relative expression of growth hormone, myogenic regulatory factor 5, and target of rapamycin was downregulated (p < 0.05) as dietary soybean meal increased from 20% to 50%. To conclude, dietary soybean meal exceeded 28% significantly inhibited growth performance of L. vannamei, mainly due to the negative impact of soybean meal on digestion and feed utilization and also the inhibition on the muscle growth and related gene expressions.

Influence of dietary soybean meal replacement with yellow mealworm (Tenebrio molitor) on growth performance, antioxidant capacity, skin color, and flesh quality of mirror carp (Cyprinus carpio var. specularis)

Yellow mealworms (TM) are currently receiving increasing attention as dietary protein source in aquaculture. A 60-day feeding trial was conducted to study the effects of dietary soybean meal (SM) replacement by TM on growth performance, antioxidant capacity, and flesh quality of mirror carp. A total of 630 mirror carp were fed seven diets containing graded concentrations of TM: YM0 (control), YM15, YM30, YM45, YM60, YM75, and YM100, corresponding to 0%, 15%, 30%, 45%, 60%, 75%, and 100% dietary soybean meal replacement. The results indicated dietary TM significantly improved the final body weight (FBW), specific growth rate (SGR), and protein efficiency (PE) (P < 0.05), except for YM100 (P > 0.05). The antioxidant capacity was promoted by increasing muscle total antioxidant capacity (T-AOC) in YM30 and superoxide dismutase (SOD) activity in TM supplemented groups (P < 0.05). The nutritional value was significantly boosted by increasing the muscle protein of YM45 and YM60 groups, the whole-body protein and muscle glycine and proline of YM60 group, and the muscle arginine of YM100 group (P < 0.05). The economic value of mirror carp also increased with the improvement of skin color by increasing yellowness (b*) (P < 0.05). Furthermore, all muscle textural parameters, fiber density, sarcomere length, and the mRNA expression of genes involved in muscle cell growth had similar change trends, increasing initially and then declining with the increase of dietary TM level. The muscle chewiness, cohesiveness, and mfr4 expression in YM15, and the adhesiveness, fiber density, sarcomere length, and mRNA expression of fgf in YM45 were higher than in the control and YM100 (P < 0.05), while no difference was found between control and YM100 (P > 0.05). The mRNA expression levels of myhc and TOR in the muscle of YM60 were significantly higher than those of the control group (P < 0.05), while there was no significant difference in YM100 (P > 0.05). According to the results of principal components analysis (PCA), the muscle textural properties in YM45 were optimal among all groups. As a consequence, TM would be able to completely replace dietary soybean meal without negative influences on growth performance, antioxidant capacity, or flesh quality of mirror carp. Finally, based on FBW, muscle crude protein, muscle fiber diameter, and protein retention efficiency (PRE), the optimal levels of dietary soybean meal replaced by TM were 50.14%, 52.43%, 53.60%, and 55.35%, respectively.

Effects of Replacing Fishmeal by Raw or Lactobacillus acidophilus-Fermented Soybean Meal on Growth, Intestinal Digestive and Immune-Related Enzyme Activities, Morphology, and Microbiota in Turbot (Scophthalmus maximus L.)

This study was performed to investigate the fermentation efficiency of Lactobacillus acidophilus and compare the effects of dietary soybean meal (SM) or L. acidophilus-fermented SM (LASM) on turbot. Two hundred and seventy juvenile turbots ( 13.50 ± 0.13 g ) were randomly divided into three treatments fed with a fishmeal-based diet (CNT) and two experimental diets with 45% fishmeal protein replaced by SM or LASM for 8 weeks. The results showed that fermentation significantly improved the essential amino acid profile, increased the lactic acid content, and reduced the antinutritional factor level in SM. Inferior growth of fish was observed in the SM group after the feeding trial, while the LASM group exhibited comparable performance to the CNT group. Activities of intestinal digestive enzymes (trypsin and diastase) and immune-related enzymes (alkaline phosphatase, acid phosphatase, and lysozyme) decreased significantly in the SM group, while no significant reduction was found in the LASM group compared to the CNT group. Dietary LASM alleviated SM-induced intestinal pathological disruption with higher villus and normal lamina propria width. Dietary LASM positively regulated the intestinal microbiota, making the overall profile more coherent with that in the CNT group. Spearman’s correlation analysis revealed that the altered intestinal microbiota was closely linked to the digestive enzyme activities. Collectively, this study indicated that L. acidophilus fermentation significantly improved the nutritional quality of SM and relieved SM-induced adverse effects on turbot, in terms of growth, intestinal digestive and immune-related enzyme activities, morphology, and microbiota.

The Effect of First Feeding Exposure of Larval Largemouth Bass to a Formulated Soybean Meal‐Based or Soy Saponin‐Supplemented Diet on Fish Growth Performance and Gut Microbiome

AbstractThe negative effects of dietary soybean meal (SBM) can be counteracted with the use of nutritional programming (NP). Nutritional programming is an early feeding event during larval or juvenile stages that can alter physiological responses of the fish later in their life. The objective of this study was to assess the effect of introducing diets containing SBM or soy saponin to larval Largemouth Bass Micropterus salmoides on growth performance and gut microbiome composition of the fish in their pre‐adult stage.The study found that NP introduced with a formulated SBM diet or dietary saponin for 21 d during the larval stages did not improve SBM utilization and growth performance in the pre‐adult age, which likely resulted from poor utilization of dry feeds in Largemouth Bass during first feeding. Our study also found that NP with an SBM diet or dietary saponin did not have any significant effects on the Largemouth Bass gut microbiome, and there did not seem to be any gut microbiome modification associated with NP. However, age‐related changes in the gut microbiome were documented.

The use of dipeptide supplementation as a means of mitigating the negative effects of dietary soybean meal on Zebrafish Danio rerio

Soybean meal (SBM) inclusion in aquaculture diets has been found to negatively affect growth and induce intestinal inflammation in fish. The objective of this study was to determine the effect of health-promoting dipeptide supplementation into SBM-based feeds on growth performance, intestinal health, and muscle free amino acid composition, an indicator of dietary amino acid availability, in a zebrafish model. There were five treatment groups in this study. The first group ((+) Control) received a fishmeal-based diet. The second group ((−) Control) received SBM-based diet. The last three groups (Ala-Glu, Car, and Ans) were fed SBM-based diets, supplemented with alanyl-glutamine, carnosine, and anserine respectively. The Ala-Glu and Car groups experienced a significantly higher weight gain than the (−) Control group, weighing 35.38% and 33.96% more, respectively at the conclusion of the study. There were no significant differences in gene expression among the groups, but Ala-Glu had the highest expression of both nutrient absorption genes measured, PepT1 and fabp2. Ala-Glu had significantly longer intestinal villi, and a significantly higher villus length-to-width ratio than the (−) Control group. The Car group had a significantly higher post-prandial tissue concentration of lysine, compared to the (−) Control group. The increase in villus surface area and expression of nutrient absorption genes represent an improvement in intestinal absorptive capacity in the Ala-Glu group. The results from this study provide support for the use of alanyl-glutamine and carnosine supplementation as a means of improving growth performance of zebrafish fed with a high level SBM-based diet.

Effect of dietary soybean meal associated with feeding time on the growth performance and intestinal microbiota composition of northern snakehead

A 63-day growth trial was conducted with northern snakehead Channa argus to evaluate how rapidly its growth performance and how reproducibly its gut microbiota respond to different dietary protein sources. Four diets were formulated with different levels of soybean meal as a replacement for fishmeal (0%, 25%, 50% and 75%). Each diet was fed to three replicates of juvenile C. argus (30 juveniles per replicate, initial weight 8.65 ± 0.25 g) to produce groups G1, G2, G3 and G4 respectively. During this trial, survival rate, growth performance and intestinal microbiota composition were determined on days 9, 21 and 63. At day 9, there was no effect of the dietary soybean meal on the final weight (Wt), weight gain (WG) and specific growth rate (SGR) between the four groups (p > 0.05). However, at day 21 (p < 0.05), they were significantly lower in G4 fish than that in G1 and G2. The highest Wt, WG and SGR were found in G1 and G2 fish, the lowest growth was found in G4 fish at day 63 (p < 0.05). Furthermore, higher operational taxonomic units (OTUs) and alpha diversity were found in G4. With the dietary soybean level increased, the proportion of Firmicutes, Bacteroidetes and Verrucomicrobia, as well as some genera of bacteria (Carnobacterium, Cetobacterium, Planctomyces, Shewanella and Thermomonas) significantly increased in the G3 and G4 fish (p < 0.05). However, the OTUs, Chao index, and the proportion of Firmicutes and some genera (Acinetobacter, Bacillus and Geobacillus) in G4 fish were significantly higher at days 21 and 63 than that at day 9 (p < 0.05). Taken together, in response to dietary soybean meal levels, dynamic and significant changes in microbiota occurred, which then ultimately attained a new equilibrium.

Effects of dietary soybean meal on the digestive physiology of red seabream Pagrus major

To clarify the effects of dietary soybean meal (SBM) on the digestive physiology of red seabream Pagrus major, two isonitrogenous and isolipidic diets; a fishmeal-based diet (diet FM) and a SBM-based diet (diet SBM), were prepared and the acute and chronic effects of the diets on the digestive physiology of the fish were examined. In the acute effects trial (<48 h), the only difference observed was a lower level of trypsin activity in the intestinal content of the SBM group than the FM group, indicating that SBM administration reduces trypsin secretion on a short-term basis. In the chronic effects trial (six weeks), there were clear differences in several parameters assessed. There was a clear retardation of growth in fish fed the SBM diet, in addition to a faster gastric transit rate, stacked intestinal content, lower gallbladder weight, lower activities/gene expression levels of hepatopancreatic enzymes (trypsin, chymotrypsin, amylase and/or lipase) and reduced protease activity (trypsin and chymotrypsin) in the intestinal content compared to fish fed the FM diet. Taken together, these results indicate that feeding SBM over a long period (chronic exposure) leads to reduced storage, production and secretion of bile and pancreatic digestive enzymes. SBM protein does not appear to fully activate or stimulate the digestive system of red seabream in either the short or long term. This may be due to a lack of stimulation or to an inhibitory effect that becomes more pronounced on a long-term basis. Such inhibition of the digestive process may be one of the main reasons for the low growth performance observed in fish fed SBM-based diets.

Effects of dietary soybean meal on the bile physiology in rainbow trout, Oncorhynchus mykiss

To clarify the effect of dietary soybean meal (SBM) on bile synthesis and enterohepatic circulation in rainbow trout, three isonitrogenous and isolipidic diets; a fishmeal based diet (diet FM), a SBM based non-fishmeal diet (diet SBM) and a 1% bile acid (taurocholate) supplemented SBM diet (diet C-tau) were prepared and acute/chronic effects of the diets on the bile physiology was examined. In the acute experiment (<24 h), fish fed the SBM based diets (diet SBM and C-tau) had higher expression levels of bile acid synthesis genes, cyp7a1-2, cyp8b1-1 and cyp8b1-2 in the liver compared to fish fed the FM diet. In the chronic experiment (10 weeks), fish fed the SBM and C-tau diets had significantly lower expression levels of cyp7a1 (-1 and -2), cyp8b1 (-1 and -2) genes compared with fish fed the FM diet. On the other hand, expression of bile acid synthesis inhibitor gene shp-2 was higher in fish fed the SBM diet compared with fish fed the FM and C-tau diets. Furthermore, fish fed the SBM based diet had reduced bile acid absorption rate. These data suggest that SBM up-regulates bile acid synthesis on a short-term basis, while long-term SBM administration down-regulates the bile acid synthesis and the recovery of bile through the enterohepatic circulation. The gallbladder weights of fish fed the C-tau diet were similar to those of fish fed the FM diet whereas the actual bile acid absorption ability was still suppressed in the C-tau group. This study contributes to the general knowledge of bile physiology in teleost fish under different nutritional conditions and to develop tailored and sustainable aquaculture feeds based on SBM.

Effect of substitution of dietary fish meal by soybean meal on different sizes of gibel carp (Carassius auratus gibelio): digestive enzyme gene expressions and activities, and intestinal and hepatic histology

A 7-week growth trial was conducted to evaluate the effects of dietary soybean meal (SBM) on digestive enzyme activity of intestinal mucosa, mRNA levels of digestive enzymes in hepatopancreas, and the mid-intestinal and hepatopancreas histology of gibel carp CAS III (Carassius auratus gibelio). Four different growth phases of gibel carp (initial body weight: fry, 0.8 g; juvenile, 5.0 g; 1-year-old, 62.7 g; and broodstock, 135.6 g) were tested. Seven isonitrogenous and iso-energetic diets were formulated to contain different SBM replacement levels (0%, 20%, 40%, 60%, 80% and 100% of dietary fish meal protein), and another diet (SBMAA) contained all SBM protein and supplied crystalline amino acids. The results showed that the activities of mid-intestine trypsin, α-amylase and gamma glutamyl transpeptidase reduced with increased dietary SBM, while the chymotrypsin activity increased first and then decreased. The ultrastructures of intestinal epithelial cells and hepatopancreas cells in fry and broodstock fish were distinctly affected by 200 g kg-1 dietary SBM. Supplementation of dietary amino acid to the highest replacement groups was not sufficient to improve digestive and absorptive capacities and growth performance. Gibel carp may be adapted to dietary SBM through increase in gene expression of hepatopancreas digestive enzymes and has potential to utilize proceeded SBM as feedstuffs.

Effects of dietary soybean meal concentration on growth and immune response of pigs infected with porcine reproductive and respiratory syndrome virus1

An experiment was conducted to determine the effects of dietary soybean meal (SBM) concentration on the growth performance and immune response of pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV). Four experimental treatments included a 2 × 2 factorial arrangement of 2 dietary SBM concentrations, 17.5% (LSBM) or 29% (HSBM), and 2 levels of PRRSV infection, uninfected sham or PRRSV infected. Sixty-four weanling pigs of split sex (21 d of age, 7.14 ± 0.54 kg) were individually housed in disease containment chambers. Pigs were provided a common diet for 1 wk postweaning before being equalized for BW and sex and allotted to 4 treatment groups with 16 replicate pigs per group. Pigs were fed experimental diets for 1 wk before receiving either a sham inoculation (sterile PBS) or a 1 × 10 50% tissue culture infective dose of PRRSV at 35 d of age (0 d postinoculation, DPI). Pig BW and feed intake were recorded weekly, and rectal temperatures were measured daily beginning on 0 DPI. Blood was collected on 0, 3, 7, and 14 DPI for determination of serum PRRSV load, differential complete blood cell counts, and haptoglobin and cytokine concentrations. Infection with PRRSV increased (P < 0.01) rectal temperatures of pigs throughout the infection period, with no influence of dietary SBM concentration. Pigs in the PRRSV-infected group had lower (P < 0.01) ADFI and G:F from 0 to 14 DPI compared with uninfected pigs. In the PRRSV-infected group, pigs fed HSBM tended to have improved ADG (P = 0.06) compared with pigs fed LSBM, whereas there was no influence of SBM concentration on growth of pigs in the uninfected group. At 14 DPI, PRRSV-infected pigs fed HSBM had a lower serum PRRSV load (P < 0.05), a higher (P = 0.02) hematocrit value, and a tendency for greater hemoglobin concentration (P = 0.09) compared with pigs fed LSBM. Serum haptoglobin and tumor necrosis factor-α concentrations of PRRSV-infected pigs were lower (P < 0.05) in pigs fed HSBM at 3 and 14 DPI, respectively, than in pigs fed LSBM. Overall, increasing the dietary SBM concentration modulated the immune response and tended to improve the growth of nursery pigs during a PRRSV infection.

The effect of dietary soybean meal and soy protein concentrate on the intestinal mucus layer and development of subacute enteritis in Yellowtail Kingfish (Seriola lalandi) at suboptimal water temperature

Solvent-extracted soybean meal (SESBM) has been reported to cause subacute enteritis in certain fish species. Two 34-day experiments investigated the effects of SESBM and soy protein concentrate (SPC) on the intestinal mucus layer and development of subacute enteritis in the hindgut of yellowtail kingfish (Seriola lalandi) at 22 and 18 °C. Fish were fed increasing levels of SESBM (Exp. 1: 0 g kg−1, 100 g kg−1, 200 g kg−1, 300 g kg−1) and SPC (Exp. 2: 0 g kg−1, 200 g kg−1, 300 g kg−1, 400 g kg−1). No visual signs of inflammation in the hindgut were observed in either experiment. However, increasing dietary SESBM significantly reduced mucus layer thickness. Neutral and acidic goblet cell mucin composition increased at 18 and 22 °C, respectively. A significant positive linear relationship was evident between goblet cell number and SESBM inclusion at 18 °C. SPC inclusion and water temperature had no significant effect on mucus layer thickness or mucin composition. However, at 18 °C, goblet cell numbers decreased with SPC inclusion. Results suggest the early stages of subacute enteritis may have been manifesting in SESBM fed fish. In the long term, mucus layer alterations associated with feeding SESBM may compromise fish health. Longer-term studies should investigate the effects of feeding SESBM to yellowtail kingfish, particularly at suboptimal water temperatures.

The effect of dietary soybean meal on growth, nutrient utilization, body composition and some serum biochemistry variables of two banded seabream , Diplodus vulgaris (Geoffroy Saint-Hilaire, 1817)

This study was performed to determine the optimum level of soybean meal diets for two banded sea bream for growth performance, nutrient utilization, body composition and serum biochemistry. Two banded seabream were fed five experimental diets which were formulated replace fish meal by soybean meal at 0, 20, 30, 40 and 50%. Up to 40% of dietary fish meal was successfully replaced with no growth depression. Whole body composition of two banded seabream was not affected by soybean meal inclusion level. Total protein, triglyceride and total cholesterol of fish fed the SM50 diets were significantly lower compared to fish fed the soybean free diet. On the other hand, serum glucose level significantly increased as dietary soybean meal inclusion increased. Results showed that 40% fish meal can be replaced in diets for the two banded seabream by defatted soybean meal. Further studies to determine the inclusion level of soybean meal more than 40% with amino acid or enzyme supplementation are needed.

Short-term effects of dietary soybean meal and lactic acid bacteria on the intestinal morphology and microbiota of Atlantic salmon (Salmo salar)

The aim of this study was to evaluate the role of the intestinal microbiota in soybean meal enteritis. Three groups of Atlantic salmon (Salmo salar) were fed for 35 days with different diets: a control diet (CD) containing 510 g kg−1 fishmeal, diet 1 (D1) containing 378 g kg−1 of soybean meal and diet 2 (D2) containing D1 supplemented with two viable lactic acid bacteria (LAB). As expected, the fish fed with D1 showed clear signs of distal intestinal inflammation during the study compared with the fish fed CD. For the fish fed with D2, the addition of LAB diminished the inflammation at day 28, but did not abolish it. Microbiological analysis demonstrated that specific bacterial groups were not correlated with the development of enteritis, but were correlated with the three diets. Microbacterium, Pseudomonas, Lactococcus lactis sp. cremoris and Aeromonas VIa were correlated with the CD, Aeromonas VIb and Sporosarcina aquimarina were correlated with D1, and Alcaligenes, Acinetobacter, L. lactis sp. lactis and Carnobacterium maltaromaticum were correlated with D2. Shewanella was not affected by the diet and was present in all fish intestines. Our study suggests that LAB may modulate intestinal inflammation; however, the role of the microbiota in the aetiology of enteritis in fish still requires further study.

Effects of dietary soybean meal on growth, nutritive efficiency and body composition of cultured tench (Tinca tinca)

Summary The suitability of defatted soybean meal as a substitute for fishmeal was assessed in juvenile (25 g, average) tench, Tinca tinca, by feeding them diets containing 25 (S25), 37.5 (S37.5) and 50% (S50) soybean meal for 150 days. Soybean meal inclusion increased the relationship between essential and non-essential amino acids. Fish were hand-fed to apparent satiation; the feed intake ratio was not dependent upon the dietary soybean level. Survival was over 95% and unaffected by treatment. Growth was reduced at higher soybean meal levels. After 150 days, average weight for the fish fed soybean diets S25, S37.5 and S50 was 65.6, 59.2 and 51 g, respectively. Growth performance was evaluated on the basis of specific growth rate (SGR), final biomass, feed conversion ratio (FCR), and feed intake (FI). Maximum SGR (0.61–0.64) and final biomass (3022–3156 g) were recorded in tench fed diets containing 25 and 37.5% soybean meal. Nutritional parameters such as feed intake and feed conversion ratio were not affected by the soybean meal. Body composition was similar for tench fed the three different diets.

Effect of Dietary Soybean Meal and Phytase Supplementation on Digestibility and Phosphorus Discharge in Red Sea Bream

Effect of Dietary Soybean Meal and Phytase Supplementation on Digestibility and Phosphorus Discharge in Red Sea Bream

The effect of dietary soybean meal on growth, nutrient utilization efficiency, and digestibility of juvenile common dentex, &lt;I&gt;Dentex dentex&lt;/I&gt; (Actinopterygii: Perciformes: Sparidae)

Background. The aim of this work was to study the growth of juvenile dentex fed on cooking-extruded diets, determine the level of substitution of fishmeal by soybean meal may be without affecting the growth in this species and its digestibility. Materials and methods. The availability of defatted soybean meal as a substitute for fish meal was evaluated in juvenile (41 g on average) dentex by feeding diets containing 0%&#8211;60% soybean meal, for 97 days. Results. Survival at the end of the experiment was high (80%) except for the fish fed diets with 50% and 60% substitution. Growth, feed gain ratio, and protein efficiency ratio (PER) were slightly reduced at higher soybean meal levels. Fish fed diets containing 0% to 40% of soybean meal grew significantly more and FCR was lower than fish fed other diets. No differences were obtained for protein digestibility coefficients of experimental diets (20%, 30%, 40%, and 50% SBM). Conclusion. The results confirm the best protein level for optimum growth seems to be around 50% and 12% lipid level, and maximum soybean meal substitution of 40%.

Effects of dietary soybean meal and photoperiod cycle on osmoregulation following seawater exposure in Atlantic salmon smolts

Atlantic salmon Salmo salar juveniles were fed either fishmeal‐based diets (FM) or diets in which soybean meal (SBM) partly replaced the FM from first feeding on. The fish were kept at continuous daylight during the juvenile stage. During the last 3 weeks before reaching 100 g body mass, all fish were subjected to 12L:12D. Starting at 100 g body mass, groups of 60 fish from each feeding background were subjected to continuous light for 12 weeks (short winter), or a square‐wave photoperiod cycle to stimulate parr to smolt transformation with 8L:16D during the first 6 weeks, and then continuous light during the last 6 weeks (long winter). After the 12 weeks, 20 fish from each treatment were subjected to 0, 24 or 96 h seawater exposure at a water salinity of 34. Hypo‐osmoregulatory ability at seawater exposure was assessed by mortality, intestinal pathology, plasma ion concentrations and osmolality, gill Na+/K+‐ATPase activity and element concentrations in the cytoplasm of distal intestinal enterocytes using X‐ray microanalysis. The hypo‐osmoregulatory capacity was higher in fish kept at short winter than at long winter, apparently due to more rapid development of gill Na+/K+‐ATPase activity. Fish fed SBM suffered typical soybean meal‐induced histological alterations of the distal intestine and apparent reductions in digestive function in the more proximal gastrointestinal regions. The net osmoregulatory capacity of these fish was maintained, as indicated by higher gill Na+/K+‐ATPase activity and lower plasma Na+, Ca2+ and osmolality compared to the FM‐fed fish. Thus, feeding SBM did not impair the hypo‐osmoregulatory ability of the Atlantic salmon following seawater exposure.

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 m 2 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.