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The present study investigated the effects of short-chain fructooligosaccharides (FOS) as dietary supplements on stress, immune response, gut microbiota, growth, and survivability of three different treatment groups of Pacific white shrimp, Litopaneous vennamei, cultured in a recirculating system. The experiment was conducted over a 35-day trial period. Shrimps were fed diets, 15 times a day using automated feeder, supplemented with GOS at 0%, 0.15%, and 0.30% by weight. Denaturing gradient gel electrophoresis analysis revealed that the enteric microbial community of shrimp fed the basal diet differed markedly (<80.0% similarity coefficient) from those fed FOS-supplemented diets. However, shrimp survival, weight gain, and immune responses among the treatment groups were good but not significantly different (P > 0.05), probably due to the limited length of the feeding trial. [ABSTRACT FROM AUTHOR]

This study was designed to examine the effects of a prebiotic compound on the immune system, digestive tract histology, and stress physiology of shrimp. The specific effects of dietary supplementation of the prebiotic galactooligosaccharide (GOS or GTGOS) on shrimp health are scarce. This experiment, therefore attempted to evaluate the effects of GOS on growth, survival, intestinal microbiota, stress resistance and immune responses of Pacific white shrimp, Litopaneous vannamei. Over a 35-day trial, shrimps were fed diets, 15 times a day using automated feeder, supplemented with GOS at 0%, 0.25%, and 0.40% by weight. Shrimp survival and weight gain among the treatment groups were good but not significantly different (P >.05). Shrimp fed GOS-supplemented diets had reduced stress (glucose, P <.05) and increased immune responses (total hemocyte counts and phagocytic capacity, P <.05) compared to shrimps fed only basal diet with no supplementation. These results suggest that GOS not only changed the populations of gut microbiota but also reduced stress levels and enhanced immune response in shrimp. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to characterize the pantothenic acid deficiency signs and quantify the dietary requirement of juvenile hybrid striped bass, Morone chrysops × Morone saxatilis . A basal diet composed of fish muscle and crystalline amino acids was analyzed to contain 5 mg of pantothenate/kg and supplemented with calcium d -pantothenate resulting in five diets with graded pantothenate levels of 5, 10, 20, 30 and 40 mg/kg diet. Each diet was fed to triplicate groups of hybrid striped bass juveniles (initial average weight 1.6 g) in a recirculating system at 26.0 ± 1 °C. Fish fed the unsupplemented basal diet performed poorly in terms of growth parameters and exhibited typical signs of pantothenic acid deficiency such as hemorrhages, sluggishness, high mortality, anemia and severe hyperplasia of the epithelial cells of gill lamellae. Fish fed the diet containing 10 mg of pantothenate/kg diet performed significantly better than fish fed the basal diet but poorly when compared with the responses of fish fed diets containing 20, 30 and 40 mg of calcium d -pantothenate/kg diet. Also, pantothenic acid-deficiency signs were apparent in fish fed the diet containing 10 mg/kg diet; whereas, no deficiency signs were observed in fish fed diets supplemented with the higher levels. Based on these data, the dietary pantothenic acid requirement of hybrid striped bass was quantified at 18.8 mg/kg diet based on broken-line regression analysis of weight gain data. Statement of relevance Pantothenic acid deficiency in hybrid striped bass was characterized and the minimum dietary pantothenic acid requirement was determined to be 18.8 mg/kg based on weight gain. This information will assist in refining diet formulations for hybrid striped bass. [ABSTRACT FROM AUTHOR]

Two feeding trials were conducted to evaluate the effects of dietary supplementation with the prebiotic GroBiotic-A on juvenile Nile tilapia, Oreochromis niloticus. Juvenile fish in both trials received a basal diet composed of practical and semipurified ingredients or the basal diet supplemented with GroBiotic-A at either 1 or 2% of dry weight. Trial 1 (8 wk), was conducted with juvenile fish initially averaging 4.3 g/fish in which their performance indices, nonspecific humoral and cellular immune responses, and intestinal microbiota were characterized. In that trial, only survival was significantly affected by dietary treatment with the greatest survival (98.7%) observed for fish fed the diet containing 2% GroBiotic-A and significantly ( P < 0.05) lower survival (86.9%) for fish fed the diet containing 1% GroBiotic-A ( GBA) and intermediate survival (90.7%) for fish fed the basal diet. Trial 2 (5 wk), was conducted with larger juveniles initially averaging 6.5 g/fish to provide a more in-depth assessment of cellular immune responses, intestinal morphometric characteristics, and disease resistance of tilapia fed the three experimental diets. Fish fed the diet with 2% GroBiotic-A exhibited significantly ( P < 0.05) increased production of extracellular superoxide anion by macrophages and a distinct microbial community within the intestine compared to fish fed the other diets. No significant differences were seen in survival after controlled exposure to Streptococcus iniae although fish fed the diet with 2% GBA tended to experience reduced mortality (12.5%) compared to those fed the basal diet (35%). Thus, based on the results from both trials, supplementation of 2% GroBiotic-A generally improved survival, altered gut microbiota, and enhanced extracellular superoxide anion production of Nile tilapia. [ABSTRACT FROM AUTHOR]

A study was undertaken to examine the potential of two non-genetically modified (non-GM) soy products, differentially processed, as fishmeal (FM) replacements. Dietary protein (DP) was replaced at 50, 60 and 70% using the 3011 meal or 40, 50 and 60% with the 3032 meal. Ingredient 3011 was a cooked and solvent-extracted meal from a high protein and low oligosaccharide soy cultivar; whereas, ingredient 3032 was a cold-pressed, low fat cake ground to a meal that originated from a medium protein, low oligosaccharide, low protease inhibitor soy cultivar. Experimental diets were isonitrogenous (45% crude protein, CP), isolipidic (13% lipid), isocaloric (12.6 kJ energy kg − 1 of diet) and were balanced for lysine (3.2%) and methionine + cysteine (2%). Taurine was supplemented at 1.5% in all diets. A commercial control diet (52% CP and 13% lipid) was included for a total of eight test diets. Twenty four round tanks (330 L) were each stocked with 20, 4 g yellowtail ( Seriola lalandi ). Tanks were supplied with recirculated seawater and each diet was randomly assigned to three replicate tanks. After a 10-week feeding trial, growth, survival, feed conversion ratio, protein efficiency ratio, protein retention, condition factor and carcass proximate composition were contrasted among dietary treatments. Results indicate that juvenile yellowtail fed diets in which the 3032 meal provided 50 and 60% of DP grew significantly ( P < 0.001) better than those fed all other diets, including the FM-based (menhaden FM) and commercial control diets. Fish fed with the 3011 meal providing 50% of DP and those fed with the 3032 meal providing 40% of DP had similar growth performance which was slightly greater than the fish fed the FM reference diet. Minor intestinal histology differences were found among fish fed the 8 diets. Taken together these data indicates that the improved non-GM soybean meals supported better performance of juvenile yellowtail than fish fed the FM reference diet. No enteritis was detected even at high dietary inclusion levels. [ABSTRACT FROM AUTHOR]

Fishmeal (FM) replacement in diets for intensive aquaculture has become a high priority area for the global aquaculture industry. In this study, a twelve week growth trial was conducted with juvenile cobia (18 g initial weight) to examine the effects of non-genetically modified soybean meals as potential replacement protein sources. Genetically modified (GM) crops and their intended and unintended effects have become major topics of controversy worldwide, with several regions banning their use in food and feeds. Therefore, it is especially critical to develop and evaluate non-GM feedstuffs for use in aquaculture diets where GM products are prohibited as the global aquaculture industry continues its expansion to meet increasing demands. Navita Premium Feed Ingredients (NPFI's) 3010 solvent extracted meal and 3032 cold-pressed cake meal were utilized to replace 50, 60 or 70% and 40, 50, or 60% of FM protein, respectively and were compared to a FM based reference formulation. None of the experimental diets performed significantly different from the reference diet in terms of weight gain (WG) or specific growth rate (SGR). However the 3010 50% diet performed significantly better than the 3032 50 and 60% diets in regard to WG, SGR, and protein efficiency. There were no significant differences between the seven diets at the conclusion of the trial in regard to their effects on filet quality as determined by organoleptic testing. These two non-GM soybean protein sources appear to be valuable FM replacement options for juvenile cobia, with none of the typical indicators of intestinal enteritis developing as has been observed in various other teleost species when high quantities of commodity soybean meal have been utilized. [ABSTRACT FROM AUTHOR]

The continued expansion of intensive aquaculture activities requires that substitutes for fish meal-based protein be identified. In this study, we evaluated partial (50 and 75%) replacement of fish meal in red drum, Sciaenops ocellatus, diets with soy protein concentrate (S) and barley protein concentrate (B). Growth, feed efficiency, survival, tolerance to low temperature, and tolerance to handling in warm, hypersaline water were evaluated. Only the diet with a 50% replacement of fish meal with S yielded results comparable to fish fed a nonsubstituted fish meal diet. However, the low-temperature studies were complicated by differences in mean fish weight among the groups. The results of this study indicate S may be partially substituted for fish meal in red drum diets. [ABSTRACT FROM AUTHOR]

Juvenile channel catfish Ictalurus punctatus were fed casein-gelatin-based semi-purified test diets with graded amounts of arginine ( ARG, 0.5%, 1%, 2% and 4% of dry diet) for a 6-week period, to evaluate the effects of dietary ARG supplementation on performance indicators, levels of plasma ARG, ornithine, citrulline, glutamine and glutamate, as well as selected innate immune parameters. Incremental dietary ARG resulted in significant improvements in weight gain, feed efficiency and protein efficiency ratios, protein retention, protein deposition and arginine deposition. Fish fed the 4% ARG diet had significantly higher values for all performance indicators, although these values were not different from those of fish fed the 2% ARG diet with the exception of protein retention, protein deposition and arginine deposition. Conversely, fish fed the 0.5% ARG diet had significantly lower values for all analysed plasma amino acids. Similarly, both phagocyte superoxide anion production and neutrophil respiratory burst were significantly decreased in fish fed the 0.5% ARG diet. These results demonstrate that the indispensability of dietary ARG is not only related to optimized protein utilization for growth but also its supplementation to fish diets may significantly impact several aspects of the immune system, including phagocyte function and thus improve overall fish health. [ABSTRACT FROM AUTHOR]

Abstract: Thyroid (TH) and growth (GH) hormones, and insulin-like growth factor I (IGF-I) are anabolic regulators in fish and responsive to nutrient intake. A study was conducted to determine if previously reported growth effects of dietary arginine (ARG) in channel catfish were related to the activation of endocrine axes. In a first experiment, catfish were fed incremental levels of ARG (0.5 – 4% of diet) for 6weeks and sampled at 2-week intervals. In a second experiment, fasted (48h) fish were fed a single ration of ARG (0.5 or 4% of diet) and sampled at various intervals (0 to 72h postprandial, PP). Experiment 1 did not reveal any influence of ARG on circulating TH, GH, or IGF-I despite the significantly increased growth of fish fed ARG-enriched diets. In experiment 2, feeding the 4% ARG diet significantly increased the amplitude of pulsatile plasma GH levels and also significantly increased IGF-I mRNA in liver and muscle, (at 2h PP) and plasma IGF-I levels (at 6h PP). Although relatively infrequent sampling failed to reveal alterations in TH or GH levels in response to ARG-induced growth activation, PP high frequency sampling unveiled high amplitude pulsatile GH secretions and may be important in activating IGF production in target tissues. Additionally, expressed and secreted IGF-I exhibited discernible patterns which closely correlate with ARG-induced growth effects in catfish. [Copyright &y& Elsevier]

Aflatoxin B1 (AFB1) is a potent carcinogen that causes growth stunting, immunosuppression and liver cancer in multiple species. The recent trend of replacing fishmeal with plant-based proteins in fish feed has amplified the AFB1 exposure risk in farm-raised fish. NovaSil (NS), a calcium montmorillonite clay, has previously been shown to reduce AFB1 bioavailability safely and efficaciously in several mammalian species. This study was designed to: (1) evaluate AFB1 impact on cultured red drum, Sciaenops ocellatus, over the course of seven weeks; and (2) assess NS supplementation as a strategy to prevent aflatoxicosis. Fish were fed diets containing 0, 0.1, 0.25, 0.5, 1, 2, 3, or 5 ppm AFB1. Two additional treatment groups were fed either 5 ppm AFB1 + 1% NS or 5 ppm AFB1 + 2% NS. Aflatoxin B1 negatively impacted red drum weight gain, survival, feed efficiency, serum lysozyme concentration, hepatosomatic index (HSI), whole-body lipid levels, liver histopathological scoring, as well as trypsin inhibition. NovaSil inclusion in AFB1-contaminated diets improved weight gain, feed efficiency, serum lysozyme concentration, muscle somatic index, and intraperitoneal fat ratios compared to AFB1-treated fish. Although not significant, NS reduced AFB1-induced histopathological changes in the liver and decreased Proliferating Cell Nuclear Antigen (PCNA) staining. Importantly, NS supplementation improved overall health of AFB1-exposed red drum. [ABSTRACT FROM AUTHOR]

Abstract: The present experiment was conducted to investigate the effects of graded amounts of dietary GLN on the intestinal morphology, plasma amino acids and growth performance of juvenile channel catfish. Six experimental diets (280gkg−1 crude protein, 80gkg−1 lipid) were composed of casein, gelatin and crystalline amino acids and supplemented with 0, 5, 10, 15, 20 or 30g free glutamine kg−1. These diets were fed to triplicate groups of fish (average initial weight of 6.1) for 10weeks after which blood and intestinal samples were collected. Intestinal microstructures were positively affected by dietary GLN at the highest levels of supplementation (20 and 30gkg−1), significantly (P <0.05) increasing enterocyte and microvilli height in anterior, mid and posterior intestinal sections. Moreover, a subsequent experiment revealed that GLN supplementation significantly (P <0.05) increased the enterocyte migration rate in all sampled intestinal segments. In contrast, immunohistochemical staining of proliferating cells with mouse anti-proliferating cell nuclear antigen (PCNA), revealed an increased number of proliferating cells only at the distal intestine. Plasma amino acid levels 15h postprandial showed significantly (P <0.05) higher levels of asparagine, serine, glycine and threonine in fish fed the diet supplemented with 20g GLN kg−1 diet. Despite the consistent trend of higher values seen in fish fed the diet supplemented with 20g GLN kg−1, there were no significant (P >0.05) differences in growth-related parameters among treatments. The present results demonstrate an efficient utilization of free GLN by intestinal mucosal cells of channel catfish, which resulted in enhancement of the enteric microstructure along with increased migration rates of enterocytes and modified plasma amino acid profiles. However, these results were not translated into improved growth at the end of the 10-week feeding trial. [Copyright &y& Elsevier]

Thirty-one microsatellite markers that were previously isolated from and characterized in greater amberjacksSeriola dumeriliwere assayed for cross-species amplification in four other members of the carangid genusSeriola: the lesser amberjackS. fasciata, yellowtail jackS. lalandi, almaco jackS. rivoliana, and banded rudderfishS. zonata. The number of markers that consistently amplified and were polymorphic ranged from 16 in yellowtail jacks to 25 in lesser amberjacks. The microsatellites characterized in this study will be useful for a variety of applications, including stock structure assessments of wild fish and parentage assignments of farmed fish. Received February 7, 2012; accepted April 16, 2012 [ABSTRACT FROM PUBLISHER]

Dietary acidifiers have been recognized as beneficial in animal production including aquacultural production of fish where they confer such benefits as improved feed utilization, growth, and resistance to bacterial pathogens. If improvements in growth and immune responses by acidifier supplementation can be confirmed in shrimp, then mortalities due to diseases could be minimized, limiting the emergence of disease-resistant bacterial pathogens as a potential result of antibiotic misuse. With this in mind, a 35-d feeding trial was conducted to evaluate growth, enteric microbiota populations, and nonspecific immune responses of Litopenaeus vannamei fed diets containing the commercial acidifier Vitoxal, based on acidic calcium sulfate in an indoor temperature-controlled, recirculating culture system without any natural productivity. Experimental diets were formulated to contain 0 (basal), 0.4, 1.2, 1.6, or 2.0% acidic calcium sulfate (ACS) by weight. Shrimp fed in excess, 15 times a day using automatic feeders. Weight gain and survival among treatments were excellent, but not significantly different ( P > 0.05). Denaturing gradient gel electrophoresis analysis revealed that the enteric microbial community of shrimp fed the basal diet differed markedly from those fed the acidifier on the basis of 64.9% similarity coefficient. Shrimp fed the commercial acidifier at 1.2 and 2.0% responded significantly ( P < 0.05) better to reduced stress and displayed enhanced immune responses including hemocyte phagocytic capacity, hemolymph protein concentration, hyaline cell counts, and hemolymph glucose, compared with shrimp fed the basal diet. These results point to an enhanced performance in terms of positive shifts in the composition of enteric microbial communities as well as improved immune performance, with no changes in growth or survival. [ABSTRACT FROM AUTHOR]

Abstract: Both arginine and glutamine play important roles in tissue repair, cell replication and collagen synthesis which impact animal growth and survival. Thus, a 7-week feeding trial was conducted to determine the effects of dietary arginine and glutamine on growth performance, innate immune responses and intestinal structure of juvenile red drum, Sciaenops ocellatus (6.9±0.04g, initial average weight). Protein in all experimental diets was derived from menhaden fishmeal and dehulled, solvent-extracted soybean meal to provide isonitrogenous (44% crude protein) and isolipidic (10%) diets. The basal diet contained 0.14% glutamine and 1.72% arginine on a dry-matter basis, which exceeds the established dietary requirement of red drum. Experimental diets were prepared by supplementing the basal diet with either arginine at 1% of dry weight, glutamine at 1%, glutamine at 2%, or both arginine and glutamine at 1%, with adjustments in glycine to maintain equal nitrogen among all diets. Feed efficiency was significantly (P <0.05) improved by supplementation of glutamine at 2% and the combination of both arginine and glutamine at 1% of diet. Neutrophil oxidative radical production in fish fed the glutamine and/or arginine-supplemented diets was significantly (P =0.03) higher compared with that of fish fed the basal diet, with a synergistic effect observed in fish fed the combined arginine–glutamine diet. Significantly (P <0.05) higher serum lysozyme activity also was observed in fish fed the diet supplemented with 1% of both arginine and glutamine. Extracellular superoxide anion production by red drum macrophages was significantly (P <0.05) higher for fish fed diets with glutamine at either 1 or 2% and the 1% arginine–glutamine combination compared to fish fed the basal diet. Similarly, macrophages from fish fed the diet with glutamine at 2% and the arginine–glutamine combination at 1% produced significantly higher amounts of intracellular superoxide anion. Morphometric analyses – i.e., measurements of enterocyte, microvillus and fold heights – demonstrated positive effects of both dietary glutamine and arginine in different portions (proximal, mid and distal) of the gastrointestinal tract of red drum. In general, fish fed the diet supplemented with 2% glutamine had the greatest increases in magnitude of the chosen structures, although those fed the diet with arginine at 1% also yielded improved scores for some enteric portions. Therefore, results from the present study establish the importance of both dietary arginine and glutamine supplementation in improving feed efficiency, as well as eliciting positive changes to several components of the innate immune system and intestinal functionality of red drum. [Copyright &y& Elsevier]

Twelve ingredients obtained from new, non-genetically modified soybean cultivars as well as commercially available sources of soybean meal (SBM) were evaluated in practical feed formulations for the Pacific white shrimp, Litopenaeus vannamei , using both digestibility and growth trials. Apparent digestibility coefficients for energy (ADE) and protein (ADP) were determined using chromic oxide as inert marker and the 70:30 replacement technique. Digestibility coefficients for ADE and ADP ranged from 76.6 to 91.3% and 93.6 to 99.8%, respectively. In general, two distinct groups of high and moderate digestibility values were observed. A separate 8-week growth trial was conducted to evaluate selected SBMs using six replicate tanks per dietary treatment (10 shrimp per tank, initial weight 0.52 ± 0.04 g). An SBM-based reference diet was formulated using commercial SBM (45.3), which was then completely replaced on iso-nitrogenous basis with other experimental SBMs. Significant differences ( P ≤ 0.05) were observed in growth performance but not survival. In general, trends in digestibility values were similar to those of the growth trial. Ingredients (I)-16, I-17, I-18, and I-19 demonstrate relatively higher values in terms of digestibility as well as supporting good growth. Results indicate that genetic selection of soybean for nutritional characteristics of the meal has the potential to increase the nutritional values of SBM for shrimp feeds. Statement of relevance This study provides useful and important information of 12 varieties soybean meal in shrimp to support the aquaculture feed industry development. [ABSTRACT FROM AUTHOR]

Abstract: Various studies with fish species indicate that dietary arginine (Arg) and glutamine (Gln) supplementation may support an enhanced performance beyond simply improving weight gain. Therefore, a feeding trial was conducted to determine the effects of dietary Arg or Gln on growth performance, immune responses and intestinal morphology of juvenile hybrid striped bass, Morone chrysops × Morone saxatilis (4.1±0.02g, initial average weight). The basal diet was formulated from menhaden fishmeal and solvent-extracted soybean meal to contain 45% crude protein and 10% lipid. Arginine and Gln were singularly added to the basal diet at either 1% or 2% or both amino acids were added in combination at 1% to formulate experimental diets with adjustments in glycine to maintain all diets iso-nitrogenous. Fish were fed the experimental diets for a period of 8weeks, at the end of which final weight, specific growth rate and feed efficiency were significantly (P <0.05) higher in fish fed diets supplemented with Arg at either 1 or 2%, Gln at 1%, Arg and Gln both at 1%, but not in those fed the diet supplemented with Gln at 2%. Arginine and/or Gln supplementation tended to improve neutrophil oxidative radical production, but not significantly (P >0.05). However, significantly higher serum lysozyme activity was observed in fish fed the diet supplemented with Arg at either 1 or 2% and Gln at 1%. Intracellular superoxide anion production by hybrid striped bass macrophages also tended to increase, while extracellular superoxide anion production was significantly improved by supplementation of Arg at 1% and Gln at either 1 or 2% of diet. Morphometric analyses demonstrated positive effects of both dietary Arg and Gln on histo-morphological measurements in different portions of the gastrointestinal tract of hybrid striped bass. The 1% Arg diet resulted in the greatest increases in size of the chosen enteric structures, but the other four experimental diets also significantly improved the scores for various intestinal portions compared to fish fed the basal diet. Results from the present experiment demonstrate the importance of dietary supplementation of both Arg and Gln in improving growth performance, eliciting positive changes to several components of the innate immune system, and also benefiting the intestinal functionality of hybrid striped bass. [Copyright &y& Elsevier]

Abstract: A constraint for the expansion of cobia aquaculture is the availability of high quality formulated diets which reduce or eliminate fish meal (FM) protein. Therefore, the nutritive value of a novel soybean cultivar, Navita™ (Navita, non-genetically modified and selectively bred soy), and regular, commodity soybean meal (SBM, de-hulled, defatted, roasted and solvent-extracted) was evaluated for cobia, Rachycentron canadum via separate digestibility and growth trials. In the first experiment Navita's apparent digestibility coefficients (ADC) were higher than those of SBM for nearly every nutrient evaluated. Crude protein ADCs were 82 and 69% for Navita and SBM, respectively. Apparent DC for amino acids ranged from 68 to 109% for Navita whereas, amino acid ADCs for SBM varied from 42 to 98%. The feeding trial utilized fish of a size that more closely resembles commercial cobia stocking (1.8kg), and was conducted over a 91-day period. Experimental diets (iso-nitrogenous and iso-energetic) were formulated such that 67% of the FM protein in the reference diet was replaced by either a combination of SBM+soy protein concentrate (SPC, Solae Profine®) labeled MXSB-diet, or by a combination of SPC+Navita; Navita-diet, hereafter. A fourth experimental diet had 80% of the FM protein replaced by a combination of Navita+SPC and was identified as Navita-high. No significant differences (P >0.05) were observed in fish fed the experimental diets for feed conversion ratio, protein efficiency ratio, feed efficiency, mean daily intake, gross protein intake, gross energy intake, visceral somatic index, muscle ratio, and hepatosomatic index. Fish fed the Navita-high diet had the lowest fish in:fish out ratio (FIFO) at 0.9±0.16. These results indicate that Navita meal can be incorporated at very high levels in the diet of marine carnivorous fish such as cobia with no detriment to performance, making it a prime candidate for FM replacement in aquafeeds. [Copyright &y& Elsevier]

Abstract: The objective of this study was to evaluate the ability of NovaSil (NS) clay to sorb and mitigate the toxic effects of aflatoxin B1 (AFB1) in Nile tilapia (Oreochromis niloticus). Growth performance, targeted innate immunological function, intestinal microbial community and histology were evaluated after feeding tilapia diets with or without AFB1 and/or NS for 10weeks. Aflatoxin B1 at concentrations of 1.5 and 3.0ppm significantly (P <0.05) decreased weight gain, feed efficiency, hepatosomatic index and macrophage extracellular superoxide anion production in tilapia, regardless of NS addition to the diet. The overall results regarding the efficacy of NS were mixed; however, there was a trend (P =0.157) towards AFB1-toxicity prevention in regards to macrophage extracellular superoxide anion production. Additionally, when 0.5 and 1% NS was included in diets containing 1.5ppm AFB1, total histopathological score was lowered; however, this protective effect was not evident when fish were exposed to 3.0ppm AFB1. Denaturing gradient gel electrophoresis was performed to assess the effects of both AFB1 and NS on gut microbiota, but no significant differences were found among treatment groups. [Copyright &y& Elsevier]

The effects of four prebiotics (fructo-oligosaccharide, Bio-MOS, transgalacto-oligosaccharide and GroBiotic-A) on digestive enzymes and intestinal morphology were studied in juvenile hybrid striped bass (Morone chrysops × M. saxatilis) and red drum (Sciaenops ocellatus) using two separate 8-week feeding trials. Red drum were fed experimental diets with the four prebiotics each individually supplemented at 1% and hybrid striped bass were fed diets supplemented with GroBiotic-A at 1 and 2%. Both trials were conducted with each diet fed to apparent satiation twice per d to three replicate groups of fifteen juvenile fish. For histomorphological analysis, gastrointestinal tract (GIT) samples from three randomly selected fish per tank were taken at 4 and 8 weeks for hybrid striped bass and at 8 weeks for red drum. For both trials, GIT samples from two randomly selected fish per tank were taken at 4 and 8 weeks and analysed for pepsin, trypsin, chymotrypsin, aminopeptidase, α-amylase, lipase, and both acid and alkaline phosphatase activities. The results of the histological evaluation indicated that the inclusion of prebiotics was adequate to elicit structural changes in the GIT of both species. On the other hand, no significant changes in the enzyme activities were detected at week 8 in both species. However, there was a transient effect of Bio-MOS supplementation on the activities of aminopeptidase, α-amylase and alkaline phosphatase at week 4 in red drum only. Thus, previously observed improvements in nutrient digestibility by these fish in response to prebiotic supplementation appear to be mostly related to changes in GIT structure as opposed to the enhancement of digestive enzyme activity.