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Interaction between dissolved oxygen concentration and diet composition on growth, digestibility and intestinal health of Nile tilapia (Oreochromis niloticus)

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Abstract

The present study was undertaken to evaluate the individual and combined effects of oxygen concentration and diet composition on the growth, nutrient utilization and intestinal morphology of Nile tilapia (Oreochromis niloticus). Two recirculating aquaculture systems were used to create the difference in oxygen concentration: normoxia (6.9 mg.L-1) and hypoxia (3.5 mg.L-1). Two diets were formulated using a different soybean meal (SBM) content to create a contrast in the potential to affect the gut barrier function. Triplicate groups of 35 fish with initial mean body weight of 23 gram were fed “Control” diet containing 20% fish meal and “Test” diet containing only plant protein source at normoxia and hypoxia for 8-weeks. Six fish per treatment were sampled for intestinal morphological analysis at the end of week 1, 4 and 8. The proximal, middle and distal intestine were processed for quantitative histology, in order to count goblet cells (GC) and eosinophilic granulocytes (EG); and to measure the thickness of lamina propria (LP) and sub-epithelial mucosa (SM). The study showed that growth was best in the “Control” diet under normoxia , while no interaction between oxygen and diet composition was found. Hypoxia reduced nutrient digestibility significantly (P < 0.05). For the “Test” diet, the decline in digestibility was larger than for “Control” diet over time. Both diet composition and oxygen level induced changes in intestinal morphology of Nile tilapia. We observed a thickening of the LP and SM caused by an increased infiltration of inflammatory cells, and an increased number of GC and EG among the enterocytes. The negative effect of increased soybean meal on intestinal morphology was enhanced at low oxygen level, and aggravated in time. The SBMenteritis-like symptoms were more pronounced in the proximal than in the distal intestine of Nile tilapia.

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... Nutrient digestibility in most fish species have been studied in relation to nutritional/dietary factors (Köprücü and Özdemir, 2005;Tram et al., 2011;Zhou and Yue, 2012). Only a few studies addressed the impact of environmental factors such as temperature in Atlantic salmon (Salmo salar) (Ng et al., 2004) or oxygen concentrations in Nile tilapia (Tran-Ngoc et al., 2016) on nutrient digestibility. In general, several studies on tilapia spp. ...
... The inclusion of soybean meal (SBM) in the diet of the carnivorous Atlantic salmon was associated to the reduction of the integrity of the intestinal barrier function (Baeverfjord and Krogdahl, 1996;Krogdahl et al., 2003;Knudsen et al., 2008). Also in Nile tilapia, an omnivorous species, recent studies have shown that the intestinal morphology can be affected by the presence of SBM in the diet causing mild to moderate enteritis (Mahmoud et al., 2014;Tran-Ngoc et al., 2016). ...
... Most studies focus on just one single stress factor and how it affects intestinal morphology. Recently, it was demonstrated in Nile tilapia that the impact of dietary SBM inclusion on digestion as well as intestinal morphology was enhanced when fish were exposed to hypoxia compared to normoxia (Tran-Ngoc et al., 2016). The potential impact of the interaction of different stress factors received less attention thus far. ...
... When animal protein ingredients are replaced by plant-based ingredients, fish get exposed to a series of "foreign" components such as starch and anti-nutritional factors that can interfere with the natural processes occurring in the intestine (Steiner and Encarnacão, 2010). In Nile tilapia, several reviews have dealt with the subject of replacing fish meal by plant protein based diets (Tram et al., 2011, Zhou and Yue, 2012, Vidal et al., 2015, Figueiredo-Silva et al., 2015, and more recently, Tran-Ngoc et al. (2016a) showed that soybean meal combined with an environmental factor had negative effects on the intestinal morphology of Nile tilapia, but the information regarding how the intestinal morphology is affected by other plant-based ingredients is still scare. ...
... The inclusion of soybean meal (SBM) in the diet of the carnivorous Atlantic salmon was associated to the reduction of the integrity of the intestinal barrier function (Baeverfjord and Krogdahl, 1996, Krogdahl et al., 2003, Knudsen et al., 2008. Also in Nile tilapia, an omnivorous species, recent studies have shown that the intestinal morphology can be affected by the presence of SBM in the diet causing mild to moderate enteritis (Mahmoud et al., 2014, Tran-Ngoc et al., 2016a. ...
... The light microscopy regions were evaluated based on the quantitative method developed at Wageningen University for salmon (Urán, 2008), which was adapted for the response to SBM-induced enteritis in Nile tilapia (Tran-Ngoc et al., 2016a). Briefly, the S a l i n i t y : g r o w t h , d i g e s t i b i l i t y a n d g ...
... Studies on the use of organic acids in tilapia diets are numerous; however, discrepancies between studies results are often high (Elala & Ragaa, 2015;Hassaan, Wafa, Soltan, Goda, & Mogheth, 2014;Ng, Koh, Sudesh, & Siti-Zahrah, 2009;Zhou et al., 2009). Recently, Tran-Ngoc et al. (2016) showed that both dietary and environmental conditions affect the intestinal morphology of Nile tilapia, and their negative impacts amplified each other. Based on this observation, we hypothesize that the variability on the results using organic acids found in literature may be related to variations in the culture conditions, more specifically regarding water and diet quality. ...
... The control diet contained 520 g/kg of soybean meal (SBM; Table 1) was formulated with the aim to challenge the intestinal morphology of Nile tilapia as shown by Tran-Ngoc et al. (2016). ...
... OA supplementation had a positive impact in the digestibility of protein and energy under the normoxic conditions but these effects were more pronounced in the hypoxic period. Tran-Ngoc et al. (2016) showed that the combination of hypoxia and a SBM-based diet reduced protein digestibility in Nile tilapia, that goes in agreements with the present results where the reduction and differences on protein digestibility between control and OA-supplemented diets became even more evident from normoxic to hypoxic period. Tran-Duy, Schrama, van Dam, and Verreth (2008) suggested that the reduced nutrient digestibility at hypoxic conditions is caused by hampering the energy expenditure and consequently reducing the nutrient absorption. ...
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The impact of two dietary organic acids (OAs) on nutrient digestibility and intestinal morphology was determined in Nile tilapia under conditions of dissolved oxygen in the water: normoxia and hypoxia. Four diets designated as control (0 g/kg organic acid salt), KDF (2 g/kg potassium diformate), CAB (2 g/kg calcium butyrate) and their combination (4 g/kg of a mixture of KDF and CAB, ration 1:1) were formulated with 520 g/kg of soybean meal in order to produce soybean meal enteritis‐like symptoms. The four diets were tested first under normoxic conditions (6 mg/L) for a period of 5 weeks, followed by a test period under hypoxic conditions (3 mg/L). The results showed that OAs were unable to significantly improve growth and nutrient digestibility under normoxic conditions but under hypoxic conditions, there was a significant enhancement of the growth and nutrient digestibility. Fish fed OA‐supplemented diets showed improvements in the intestinal morphology under the normoxic conditions, and these effects were more pronounced under the hypoxic conditions. Experimental findings suggest that OAs can improve the nutrient digestibility and intestinal morphology under hypoxic conditions. A synergistic effect by the combination of formic and butyric acid on growth, digestibility and intestinal morphology was not found.
... The starch fraction of the diet is considered highly digestible with apparent digestibility coefficients (ADC) of 90%, up to 99% in Nile tilapia (Amirkolaie et al., 2006;Haidar et al., 2016;Leenhouwers et al., 2007a). The ADC of the total carbohydrate fraction has been found to be as low as 30-60% (El-Saidy and Gaber, 2003;Deng et al., 2016) and as high as 80-2 90% for Nile tilapia (Tran-Ngoc et al., 2016;Sintayehu et al., 1996). The large variation in the digestibility of the total carbohydrate fraction is mainly caused by differences in the total dietary fibre fraction. ...
... Number of diets Köprücü and Özdemir, 2005;Amirkolaie, 2006;Leenhouwers et al., 2007a;El-Saidy and Gaber, 2003;Amirkolaie et al., 2006;Amirkolaie et al., 2005;El-Shafai et al., 2004;Obirikorang et al., 2015;Gaber, 2006;Gaber, 2005;Degani et al., 1997;Sintayehu et al., 1996;. § Dong et al., 2010;Schrama et al., 2012;Haidar et al., 2016;Tran-Ngoc et al., 2016;Deng et al., 2016. from 12 to 95%, with an average of 67%. ...
... The fish continue to live in these suboptimal conditions without exhibiting any obvious problems like daily mortality. Makori et al. [22] reported that O. niloticus can continue growing in suboptimal conditions of pH and conductivity and observed that under such circumstances, growth was negatively affected. The inevitable consequence of hampered fish growth is reduced overall aquaculture production. ...
... Various previous workers have recorded varying levels of electrical conductivity in fish ponds and concluded that they were within safe ranges. For instance, Makori et al. [22] reported a high growth rate of O. niloticus in pond water with a lower conductivity (77 µS cm -1 ) than that reported in the present study. Danesh et al. [23] reported conductivity of up to 450 µS cm -1 as being within the safe and suitable range for optimum O. niloticus growth. ...
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In an effort to attain food security, Kenya has embraced aquaculture as one of its strategies. From 2009, the Government established thousands of fish ponds through the Economic Stimulus Programme (ESP). Tharaka-Nithi County was one of the places covered by the ESP and has 95% of its total ponds under the programme, stocked with the Nile tilapia (Oreochromis niloticus). Physicochemical properties of water influence overall pond productivity and fish yields. The ponds in Tharaka-Nithi County have suffered low production, the average production remaining at <30% of potential, with reports of stunting and frequent fish mortalities. This study aimed to investigate the physicochemical properties of the pond water in the county. Using the randomized complete block design (RCBD), the study area was divided into three zones whereby 27 fish ponds were studied. Chemical analysis was done according to the APHA Standard Methods and data analyzed using the one-way ANOVA. The Statistical Package for the Social Sciences (SPSS) Version 22.0 was used for correlations and regression analyses. Significant differences (p ˂ 0.05) were found in water temperature, dissolved oxygen, transparency, pH and conductivity among ponds in the three zones. Water temperatures, ammonia and PO 4-P concentrations were outside the recommended range for optimum O. niloticus growth. Occasionally, DO and pH were outside those suitable for optimum tilapia growth, which could explain the frequent fish deaths and low aquaculture production. Regular monitoring of physicochemical parameters is recommended. These findings will be used by relevant government agencies and fish farmers to enhance fish production.
... Tilapia fed supplemented organic acids, such as potassium diformate and calcium butyrate diets exhibit more pronounced improvements in intestinal morphology under hypoxic conditions than normal conditions. In the distal intestine, the tilapia have a thinner SM and LP, and fewer goblet cells, which is considered an improvement in the intestinal epithelium (37). The capacity of organic acid to strengthen intestinal morphology is strongly dependent on the conditions of upbringing (38). ...
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The human population has increased considerably worldwide, including in the Philippines. Aquaculture is one of the main food sectors that provides a cheap source of protein in the Philippines. Changes in diet composition in aquacul‑ ture have brought about concerns regarding certain negative effects at the gastrointestinal levels. The replacement of fish meal with a plant protein source in a considerable proportion in the diet of the majority of cultured fish species has led to proliferative and inflammatory responses in the intestines of various (functionally) monogastric animals. In aquacul‑ ture feed, the dietary supplementation of organic acids and their salts as growth promoters has been established. The use of acidifiers in aquafeed requires a different approach due to diversified feeding habits and the wide variation in the digestive system structure and physiological function. Dietary organic acids can increase pancreatic enzyme production, decrease stomach pH levels, inhibit pathogens, provide energy, improve mineral utilization and improve nutrient digestibility, all of which improve fish development performance. Acidifiers are currently widely used in animal feed, including aquafeed, and several manufacturers have created next‑generation acidifiers with additional benefits. The present review article discusses the acidifiers, their mechanisms of action, growth, feed efficiency, immunity and future research opportunities. The fish growth rate and feed utilization efficiency are also reviewed as regards dietary acid sources, such as acetic acid, citric acid, hydrochloric acid and control‑no acid. In addition, the attractability of the diets for the fish at different pH levels and dietary acid sources was determined. The survival rates of cultured fishes were determined based on the various dietary acids used. Any acids at an optimum pH level, e.g., pH 4.6 in the diet of tilapia fry, which increase attractability, growth and feed efficiency, warrant further attention.
... Dissolved oxygen (DO) refers to free and non-compound oxygen in water or other liquids, which is involved in various biochemical and physiological activities [1,2]. The dissolved oxygen content in water is an important indicator of the water quality and an important factor in water purification. ...
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Dissolved oxygen is an important index to evaluate water quality, and its concentration is of great significance in industrial production, environmental monitoring, aquaculture, food production, and other fields. As its change is a continuous dynamic process, the dissolved oxygen concentration needs to be accurately measured in real time. In this paper, the principles, main applications, advantages, and disadvantages of iodometric titration, electrochemical detection, and optical detection, which are commonly used dissolved oxygen detection methods, are systematically analyzed and summarized. The detection mechanisms and materials of electrochemical and optical detection methods are examined and reviewed. Because external environmental factors readily cause interferences in dissolved oxygen detection, the traditional detection methods cannot adequately meet the accuracy, real-time, stability, and other measurement requirements; thus, it is urgent to use intelligent methods to make up for these deficiencies. This paper studies the application of intelligent technology in intelligent signal transfer processing, digital signal processing, and the real-time dynamic adaptive compensation and correction of dissolved oxygen sensors. The combined application of optical detection technology, new fluorescence-sensitive materials, and intelligent technology is the focus of future research on dissolved oxygen sensors.
... Meanwhile,Emaliana et al. (2016), stated that optimum temperature on goldfish growth ranges from 26°C-31°C and oxygen levels > 4 mg/L. Moreover,Neilan & Rose (2014)reported low levels of oxygen (< 2.5 mg/L) would cause mortality increase (> 50%) in fish larvae and behavioral disturbance in juvenile of gulf killifish, whereas TranNgoc et al. (2016)reported low levels of oxygen (< 3.5 mg/L) in tilapia could reduce nutrient digestibility and intestinal morphology changes. ...
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In fish culture, optimal growth could be influenced by various culture methods. Aim of the study was to evaluate the productivity of Barbonymus balleroides, lalawak in floating net cages, concrete ponds, and earthen ponds. Cultivation was designed with the circulation water system. Experiment was conducted using completely randomized design with three treatments and three replications for each treatment. The experimental fish, sized of 4.20 ± 0.64 cm SL and weight of 2.14 ± 0.99 g, were obtained from induced breeding. The stocking density used was 20 individuals/m3. Fish were fed 3% of total weight two times every day using commercial pellet with 35% protein content for 90 day. The result showed that lalawak reared in earthen pond was no significant difference on length, weight, and biomass compared with that one in concrete pond (P>0.05), but significantly different (P<0.05) with floating net cages. There were no different (P>0.05) among the three different culture systems for survival rate and FCR. Lalawak reared on earthen pond system supported with optimal water quality could increase productivity value.
... For example, impaired intestinal barrier function along with morphological changes in proximal and DI (Sundh et al., 2010) and elevated mucosal neutrophil infiltration (Niklasson, Sundh, Fridell, Taranger, & Sundell, 2011) have been previously reported to occur in response to chronic hypoxia in Atlantic salmon. It has also been shown that the degree of diet-induced intestinal morphological changes was aggravated in Nile tilapia (Oreochromis niloticus) kept under hypoxic conditions (Tran-Ngoc et al., 2016). ...
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This study investigated morphological changes associated with soya bean meal-induced enteritis (SBMIE) in distal intestine (DI) of rainbow trout (Oncorhynchus mykiss) fed a soya bean meal (SBM)-based diet and exposed to normoxia or hypoxia created by optimal and low water flow rates, respectively. A 28-day adaption period was followed by a 42-day challenge period where 600 fish were subjected to dietary challenge and/or hypoxia. Twelve tanks each containing 50 juvenile trout were assigned randomly in triplicate to each treatment. Histopathological and immunohistochemical evaluation revealed pathological features that have not previously been described in association with SBMIE. Vacuolar degeneration of epithelial cells mainly at the base of mucosal folds, epithelial cysts, epithelial dysplasia, necrosis, shedding of necrotic cells, and granulomatous inflammation including infiltration of enlarged, sometimes finely vacuolated or “foamy” macrophages, multinucleated giant cells and increased proliferation of fibroblasts were observed. Acid-fast bacteria were not detected in enlarged macrophages; however, these cells contained AB-PAS- and sometimes cytokeratin-positive material, which was interpreted to be of epithelial/goblet cell origin. Hypoxia did not affect the morphological changes in DI. These results suggest that SBM was associated with a granulomatous form of enteritis in DI of rainbow trout regardless of water oxygen level.
... Pada budidaya ikan, contohnya ikan nila, perubahan berat akhir secara signifikan terjadi dengan menaikkan konsentrasi oksigen terlarut [4]. Pada kondisi hypoxia atau kadar oksigen kurang (3.5 mg/l) kemampuan ikan mencerna nutrisi menurun derastis [5]. Dalam budidaya udang vaname, kenaikan kadar oksigen terlarut dalam kolam meningkatkan tingkat kelulushidupan dan keuntungan yang diperoleh [6]. ...
... Therefore, more energy is available for growth. Tran et al. (2016) found Nile tilapia performed significantly less in terms of final body weight, specific growth rate and FCR under hypoxia (3mgL À1 ) compared with under normoxia 5 mg/L which is 50% of saturation. They also found that hypoxia affected intestinal morphology negatively. ...
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Productivity among small‐ and medium‐scale tilapia farms varies considerably. The difference between the best performers and lower ones (yield gap), is affected by differences in growth rate and feed conversion ratio (FCR). FCR at the farm level is strongly influenced by survival of fish. In this study a systematic literature review of two databases (ASFA and CAB‐Abstracts) identified 1973 potentially relevant articles. Data from 32 articles that met the inclusion criteria were analysed using linear mixed models for the most important factors with significant contributions to growth [investigated through analysis of the thermal growth coefficient (TGC)], survival and FCR of Nile tilapia. Increasing crude protein (CP), dissolved oxygen (DO) and pH significantly decreased FCR and increased TGC. Increasing stocking weight (SW) significantly improved both FCR and survival. Temperature had the largest effect on FCR followed by DO, pH and CP. DO had the largest effect on TGC followed by CP and pH. This study confirms that the optimal rearing temperature for Nile tilapia is between 27 and 32°C. Improving management to optimize DO (> 5 mg/L), stocking density (3–5 fish/m²), SW (> 10 g) and CP (25 − 30%) will improve performance and survival in small‐ and medium‐scale tilapia farming. However, it is hard to influence temperature in ponds and cages while DO is largely influenced by aeration. Since many small‐ and medium‐sized farms do not have aeration, these major tilapia farming systems could benefit from genetically improved strains selected for resilience to highly fluctuating diurnal temperature and DO levels.
... Several reviews addressed the fish meal replacement by plant protein in Nile tilapia diets (Figueiredo-Silva, Lemme, Sangsue, & Kiriratnikom, 2015;Tram et al., 2011;Vidal et al., 2015;Zhou & Yue, 2012). Recently, Tran-Ngoc et al. (2016) showed that SBM in combination with an environmental stressor (Baeverfjord & Krogdahl, 1996;van den Ingh et al., 1991;Urán et al., 2009), rainbow trout (Oncorhynchus mykiss) (Heikkinen et al., 2006;Venold, Penn, Krogdahl, & Overturf, 2012) and summer flounder (P. dentatus) (Bone, 2013). ...
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The present study assessed the effect of different feed ingredients on nutrient apparent digestibility coefficients (ADC), nitrogen/energy balance and morphology changes in the intestine of Nile tilapia; using a control diet and six test diets, in which the following six ingredients were included at 30%: hydrolysed feather meal (HFM), soybean meal (SBM), rice bran (RB), rapeseed meal (RM), sunflower meal (SFM) and dried distillers grains with solubles (DDGS). The proximal, middle and distal intestine was processed for quantitative histology counting the number of goblet cells (GC), and measuring the thickness of lamina propria (LP) and submucosa (SM). The study showed that the ADC of protein in raw materials were highest in SBM (92.2%), followed by SFM (90.2%), DDGS (89.2%), RM (87.8%), HFM (86.9%) and RB (84.0%). The nutrient ADCs had no correlation with intestinal morphology changes. Only the SBM diet caused noticeable changes in intestinal morphology such as an increase the thickness of SM and LP and the number of GC. The diet composition, however, altered the protein efficiency and the maintenance energy requirement. Protein retention efficiency was the lowest in fish fed HFM and the highest in RB. The highest maintenance energy requirements were observed in HFM and SBM treatments.
... The values of dissolved oxygen in these lakes varied between 2.0 and 6.0 mg/L in the MD and between 1.1 and 6.8 mg/L in the VD. The oxygen concentrations in normoxia (6.9 mg/L) and hypoxia (3.5 mg/L) significantly reduce the digestibility of nutrients and promote harmful changes in the intestinal tract of fish (Tran-Ngoc et al., 2016), while the current concentrations in the lakes were much lower than that for long periods. Harmfull effects of low dissolved oxygen were made evident when four species (Tilapia zillii, Sarotherodon galilaeus, S. melanotheron and Oreochromis niloticus) were exposed to pollutants and oxygen concentrations that ranged from 4.3 to 6.2 cm 3 /L, resulting in mortality, physiological dysfunction and respiratory impairment (Fafioye et al., 2010). ...
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... Dissolved oxygen is an indispensable substance for the aquatic organism and a vital parameter to characterize the metabolism of marine ecosystems [73][74][75]. The DO content in seawater is influenced by biochemical and physiological activities. ...
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... The starch fraction of the diet is considered highly digestible with apparent digestibility coefficients (ADC) of 90%, up to 99% in Nile tilapia (Amirkolaie et al. 2006;Leenhouwers et al. 2007;Haidar et al. 2016). The ADC of the total carbohydrate fraction has been found to be as low as 30-60% (El-Saidy & Gaber 2003;Deng et al. 2016) and as high as 80-90% for Nile tilapia (Sintayehu et al. 1996;Tran-Ngoc et al. 2016). The large variation in the digestibility of the total carbohydrate fraction is mainly caused by differences in the total dietary fibre fraction. ...
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Currently, studies reporting the digestibility of carbohydrates, starch and especially non-starch polysaccharides (NSP) in fish are scarce. Carbohydrate digestibility in the diet is largely dependent upon carbohydrate composition (starch vs. NSP). NSP are often considered to be indigestible and thus of no nutritional value. The present study reviews carbohydrates in fish feed, distinguishing between total carbohydrate, starch and NSP. Besides a qualitative approach, a meta-analysis was performed, compiling available data from digestibility studies on tilapia. Our meta-analysis confirms the negative effect of NSP on performance (FCR) and nutrient digestibility (crude protein, fat and energy). However, an average NSP digestibility of 24.3% was calculated in 95 cases. Out of these 95 cases, 88% of them showed a positive NSP digestibility. NSP digestibility was shown to contribute to energy digestibility. The digestion of NSP in fish is associated with fermentation in the gut, producing beneficial volatile fatty acids that are rapidly absorbed by the colonic lumen. Therefore, in diet formulation, digestibil-ity and thus energy originating from NSP should be taken into consideration because NSP contribute to the energy needs of fish, here tilapia. Besides being an energy source, specific types of NSP may have immune-modulating and prebiotic effects and may be increasingly added to fish feed as modulators of fish health. We suggest that NSP is potentially (partly) digested by a wide range of fish species , especially by warm-water species with a long gut adapted to feeding on plant matter, as these factors favour gut fermentation.
... Dissolved oxygen is one of the main factors that affect FCR and growth of Nile tilapia (Mengistu et al., 2019). Under hypoxia (3 mg/l), Nile tilapia significantly underperform in terms of FCR and growth compared to normoxia (5 mg/l) (Tran et al., 2016;Mengistu et al., 2019). In summary, our results confirm the findings of Mengistu et al. (2019) that aerating ponds results in a higher mean harvest weight, survival, and lower FCR. ...
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A major problem in smallholder Nile tilapia (Oreochromis niloticus) farms is that the achieved production is much lower than under optimal management. One of the main environmental factors contributing to lower production is dissolved oxygen (DO), because the majority of Nile tilapia production takes place under smallholder farms with no aeration of ponds which leads to large DO fluctuations. On the contrary, breeding programs select fish in aerated ponds. Aerating ponds is currently not an option for smallholder farmers because either it is too expensive or they lack access to cheap electricity supply. Therefore, it is crucial to know the genetic correlation between aerated and non-aerated ponds to optimize breeding programs to select fish that perform well in ponds with fluctuating DO levels. The objectives of this study were 1) to investigate the presence of genotype by environment (GxE) interaction between aerated and non-aerated earthen ponds using a design that minimized common environmental effects and 2) the impact of (non-)aeration on genetic parameters. The experimental fish were mass-produced using natural group spawning and nursed in four 30m² hapas. A random sample of fingerlings from each hapa was tagged and randomly distributed to aerated and non-aerated ponds for a grow-out period of 217 and 218 days. Body weight and photographs were taken on five consecutive time points during grow-out. Of the stocked fish, 2063 were genotyped-by-sequencing. A genomic relationship matrix was built using 11,929 SNPs to estimate genetic parameters with ASReml. No-aeration significantly reduced mean harvest weight (HW), survival and thermal growth coefficient (TGC) compared to aeration. Substantial heritabilities (0.14–0.45) were found for HW, TGC, surface area (SA) and body shape, expressed as ellipticity, and low heritabilities (0.03–0.04) for survival in aerated and non-aerated ponds. In both ponds, the environmental effect common to full sibs was not significant. Genetic coefficients of variation were 20–41% lower and heritabilities were 19–25% lower in the non-aerated pond compared to the aerated pond, for HW, TGC and survival. Genetic correlations between ponds for HW, standard length, height, SA and TGC were 0.81, 0.80, 0.74, 0.78 and 0.78, respectively. In summary, some GxE interaction between aerated and non-aerated ponds was found and no-aeration decreased genetic coefficients of variation and heritabilities compared to aerated ponds. Breeding programs are recommended to use half sib information from non-aerated farms or to set up a reference population for genomic selection in a non-aerated environment either on-station or in farms.
... The values of dissolved oxygen in these lakes varied between 2.0 and 6.0 mg/L in the MD and between 1.1 and 6.8 mg/L in the VD. The oxygen concentrations in normoxia (6.9 mg/L) and hypoxia (3.5 mg/L) significantly reduce the digestibility of nutrients and promote harmful changes in the intestinal tract of fish (Tran-Ngoc et al., 2016), while the current concentrations in the lakes were much lower than that for long periods. Harmfull effects of low dissolved oxygen were made evident when four species (Tilapia zillii, Sarotherodon galilaeus, S. melanotheron and Oreochromis niloticus) were exposed to pollutants and oxygen concentrations that ranged from 4.3 to 6.2 cm 3 /L, resulting in mortality, physiological dysfunction and respiratory impairment (Fafioye et al., 2010). ...
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... The values of dissolved oxygen in these lakes varied between 2.0 and 6.0 mg/L in the MD and between 1.1 and 6.8 mg/L in the VD. The oxygen concentrations in normoxia (6.9 mg/L) and hypoxia (3.5 mg/L) significantly reduce the digestibility of nutrients and promote harmful changes in the intestinal tract of fish (Tran-Ngoc et al., 2016), while the current concentrations in the lakes were much lower than that for long periods. Harmfull effects of low dissolved oxygen were made evident when four species (Tilapia zillii, Sarotherodon galilaeus, S. melanotheron and Oreochromis niloticus) were exposed to pollutants and oxygen concentrations that ranged from 4.3 to 6.2 cm 3 /L, resulting in mortality, physiological dysfunction and respiratory impairment (Fafioye et al., 2010). ...
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... As an organ that is in direct communication with the external environment, the gut is susceptible to structural changes triggered by multiple environmental factors (Tran-Ngoc et al. 2019), and in this regard, it has been demonstrated that under conditions of hypoxic stress, there is a reduction in the length of the gut villi in Lateolabrax maculatus, as well as in the number of goblet cells, and that the villi become more sparsely distributed (Dong et al. 2020). Conversely, the number of gut goblet cells in tilapia has been observed to undergo a significant increase in a low-oxygen environment (Tran-Ngoc et al. 2016). In the present study, we observed a reduction in the length of villi in the guts of mudskippers maintained in a semi-aquatic environment, whereas villus width was found to increase. ...
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A 14-day experiment was conducted to explore the pathological process and immune response of soybean meal (SBM) induced enteritis (SBMIE) in grass carp (Ctenopharyngodon idellus). The complete replacement of dietary fish meal (FM) with SBM resulted in a remarkable reduction in final body weight, weight gain ratio, and feed conversion efficiency (p < 0.05). The typical histopathological changes of SBMIE appeared starting at day 4, and progressively increased in severity until day 8, then gradually subsided after day 11. The course of SBMIE could be divided into incubation period (days 1-2), prodromal period (days 3-6), symptomatic period (days 7-10), and convalescent period (days 11-14). Transcription levels of pro-inflammatory cytokines, including IL-1β, TNF-α, IL-6, IL-8, IL-17A/F1 and IFN-γ2, were up-regulated during the prodromal period, and then down-regulated during the convalescent period. Transcript levels of anti-inflammatory cytokines (IL-10 and TGFβ1) and their receptors (IL-10R1 and TβRII), were up-regulated during the prodromal and convalescent periods. Transcript levels of MHCIIβ, Igμ, Igτ, TCRδ, TCRβ, CD4, and CD8α were altered in SBMIE. Furthermore, expression levels of T-bet, IFN-γ2, RORγ2 and IL-17A/F1 were significantly increased in the initiation of enteritis, whereas the transcript levels of Foxp3 and IL-2/15Ra were significantly up-regulated in the repair of enteritis. In conclusion, grass carp SBMIE is regulated by the adjustment of SBM-based diet intake, and the changes of the above-mentioned genes expression suggest that these genes may be involved in SBMIE.
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This manuscript describes the importance of using histological methods to assess the effects of feed on the liver and intestine of fish. Due to the constantly increasing world production of fish and other aquatic organisms, it is necessary to replace fishmeal and fish oil in diets with less expensive raw materials of plant origin. Due to the increased fiber content, increased presence of carbohydrates, antinutritional factors, and inappropriate content of amino acids and new compounds can have negative effects on the digestive system of fish and therefore on fitness, health and production characteristics of cultivated fish. The liver and intestines are the most important organs for the digestion and absorption of nutrients from feed. Therefore, monitoring histological structure of fish liver and intestine is the method of choice in assessing the effects of nutrient mixtures that use raw materials of plant origin. For both of these vital organs the normal histological structure and the most important results obtained by research are discussed. This paper presents a critical review of the histological methods used in research on feed effects. Results related to the negative effects of raw soy-based feed on the occurrence of enteritis in carnivorous fish species are discussed. The results point out that use of modern approach in fish pathology such as improved histochemical, stereological, scoring, and other analytical methods could be a beneficial approach in an accurate assessment of new feed effects on fish.
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ABSTRACT The influence of dissolved oxygen concentration on gill histopathology of great sturgeon (Huso huso) was evaluated in two weight classes (initial weight 280.9±49.2 g and 1217.9±138.1 g respectively). Oxygen treatments included hypoxia (2-3 mg/l), normoxia (5-6 mg/l) and hyperoxia (9-10 mg/l). The fish were acclimated to experimental tanks for one week then randomly distributed into 9 tanks in each of the initial weight classes (3 and 6 fish per tank in higher and lower initial weight classes respectively) for 8 weeks. In order to find the histopathological changes, gill samples were collected, dehydrated through ethanol series, embedded in paraffin , sectioned at 7 μm thickness using a Leitz microtome and stained with H & E. No mortality was observed over the 8 weeks of the experimental period. There were significant differences in weight and feed intake between treatments in the both weight classes (P<0.05). Fork length showed significant differences in lower initial weight class (P<0.05). The main histopathological changes were observed in gills including: Hyperplasia, loss of secondary lamellae, hemorrhage and congestion in primary and secondary lamellae, lamellar fusion, epithelial lifting in secondary lamellae, clubbing of secondary lamellae, telangiectases, increase in melanin pigments and numerous vacuoles in primary and secondary lamellae (in hyperoxia treatment). All these lesions may reduce gill functional surface of gaseous exchange, impairing respiratory function. Keywords: Fish, sturgeon, hypoxia, normoxia, hyperoxia, gill
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The salmonid intestinal epithelium is important for growth and health of the fish. The epithelium is exposed to a multitude of internal and external factors that can influence its function. During the parr-smolt transformation and subsequent seawater transfer, the epithelium adapts for an osmoregulatory role and the fish starts drinking seawater (SW). Endocrine signals increases the intestinal water uptake partly through an up-regulation of Na+,K+-ATPase activity. It is shown that the epithelial paracellular permeability decrease concurrent with the increase in water transport, suggesting that water flow is directed from a paracellular to a more transcellular route. The rational for this could be the increase in epithelial exposure to the environment at SW entrance. Tightening the paracellular route could be a mechanism to reduce paracellular transfer of harmful substances and pathogens. A major salmonid pathogen is the bacterium Aeromonas salmonicida, which cause losses in both aquaculture and in wild populations. It is not known, however, by which route the A. salmonicida enters the fish. A. salmonicida has been positively demonstrated in the intestinal lumen but it has been controversial whether or not the bacteria cross the epithelial barriers. It is demonstrated that A. salmonicida can translocate across the intestinal barrier, indicating the intestine as a functional route for bacterial infection in salmonids. It is concluded that A. salmonicida employs many virulence mechanisms, such as exotoxins, endotoxin and cell bound factors, to disrupts epithelial morphology and function and promote translocation. During the later phases of parr-smolt transformation the epithelial barrier integrity decreased and translocation of pathogens increased. The increased disease susceptibility during this life stage could thus partly be caused by a decreased barrier function. Vegetable lipids are used as replacement for fish oil in salmonid aquaculture, but there are concerns about how the new diets affect the intestinal epithelium. The epithelial functions presently investigated indicate a slight increase in permeability, supporting earlier histological reports of epithelial disruptions but not to the same extent. Nutrient uptake and barrier function during the parr-smolt transformation was significantly improved by a vegetable lipid-containing diet, indicating that this inclusion may be beneficial in the freshwater (FW) stage. The fatty acid profile of the natural diet for salmonids in FW is more similar to a blend of vegetable oils than to the profile of marine feed ingredients, routinely used in salmonid aquaculture. This may be the rationale for the positive effects. Salmon fed sunflower oil, however, showed long term elevation of plasma cortisol levels indicating a chronic stress. As chronic stress is known to depress immune function, specific vegetable lipids potentially stressful to the fish may also affect their health and welfare. Thus, while vegetable lipids at certain life stages are feasible substitutes for fish oil, possible long term stress effects by vegetable oils should be considered. In conclusion, the salmonid intestinal epithelium is a sensitive and dynamic tissue which is affected by external factors, such as pathogen bacteria, environment and diet, but which also can be endogenously regulated to compensate for this disturbance. ISBN: 978-91-628-6834-5
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Two experiments were conducted to determine the effect of phytic acid on nitrogen retention in tilapia (Oreochromis niloticus). The first experiment utilized graded levels of soybean meal (SBM) with or without hydrolysis of phytic acid. The second experiment utilized diets containing graded levels of purified phytic acid. In the first experiment, weight gain was inversely related to SBM inclusion beyond 250 g kg−1 of the crude protein (CP). Broken-line and quadratic models were applied to the growth data. The models suggest limiting inclusion to 380 and 170 g kg−1 CP for untreated and phytase treated SBM, respectively. The two SBM treatments exhibited similar trends in efficiency parameters. However, significant differences (P < 0.05) within treatments appeared when phytase treated SBM surpassed 250 g kg−1 CP, but not until 750 g kg−1 CP with untreated SBM. At similar rates of SBM incorporation, apparent net protein utilizations with untreated SBM were significantly higher beyond 250 g kg−1 CP (P < 0.05). In the second experiment, phytic acid did not affect efficiency parameters until the concentration was twice that in diets incorporating SBM as 1000 g kg−1 CP in a 330 g kg−1 CP diet. Phytic acid does not reduce nitrogen retention in tilapia, and its removal from SBM may decrease nitrogen retention.
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Groups of Atlantic salmon (Salmo salar L.) in feeding (guts filled with faeces) or fasted (three days of diet deprivation) states were subjected to 15 minutes of acute stress. Blood samples and intestinal tissue were collected and prepared for chemical and ultrastructural analyses at intervals post stress until 53h of recovery. Subjecting fish to acute stress led to significant alterations of the ultrastructure of the enterocytes lining the gastrointestinal tract (GI tract). The most notable effect was substantial damage to the intercellular junctional complexes in midgut regions. These effects appeared within the first hour after stress, were maintained for at least 12h and were more pronounced in fed than fasted fish. In contrast, hindgut was influenced less by stress and damage was rarely observed. Stress also influenced fish intestinal microbiota. Adherent bacteria decreased in both midgut and hindgut of stressed fish, and this was accompanied by a significant increase in the bacterial contents of faeces. It is suggested that this was due to the sloughing off of mucus eliminating existing microflora and allowing remaining bacteria (also pathogenic) in the gut lumen to colonize the surface of the enterocytes. Although blood haematocrit and plasma cortisol increased following stress, the response appeared to be greater in fasted fish. There were also significant differences in carbohydrate metabolism. While liver glycogen stores were depleted in fasted fish following the mobilization of glucose into plasma, liver glycogen was never depleted in fed fish. As a consequence, plasma glucose levels remained high for more than 12h of recovery. In fed fish, plasma lactate was also higher than in fasted salmon, and the clearance rate appeared slower. Acute stress induced oxidative stress, as measured through plasma malondialdehyde, but the effect was marginal and nonsignificant.
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Soybeans contain phytates, the anionic forms of 1,2,3,5/4,6-hexakis (dihydrogen phosphate) myoinositol, with the potential to reduce amino acid (AA) availability. Tilapia lack the intestinal enzyme phytase to hydrolyze phytates. Oreochromis niloticus (approximately 68 g) were fed diets containing either phytase pretreated or untreated soybean meal (SBM) incorporated at 0, 25, 50, 75, or 100% of the crude protein (CP) in a 33% CP diet to determine whether phytates reduce CP digestibility and AA availability. There were no differences in apparent CP digestibility. Dietary and available methionine (Met), and available lysine (Lys), decreased with increasing incorporation of phytase pretreated SBM. Reduced availability of Met and Lys from the phytase pretreated diets was likely due to removal of phytates. Phytates may reduce the effect of other antinutritional factors, protect amino acids from degradation, or decrease leaching of water soluble components.
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In this study, apparent digestibility coefficients (ADCs) of nutrients and energy in selected feed ingredients were determined for Nile tilapia. ADCs were determined using a reference diet with chromic oxide indicator and test diets that contained 70% reference diet, by weight, and 30% of the test ingredient being evaluated. Fish were fed twice daily at the rate of 4% of their body weight at 27±1 °C of water temperature. Fecal samples were collected from three replicate groups of fish using fecal collection column attached to fish rearing aquaria. The ADCs of the anchovy meal, corn gluten meal, soybean meal, gammarid meal and crayfish exoskeleton meal were: dry matter, 91.6%, 93.2%, 90.9%, 77.0%, and 75.7%; protein, 90.5%, 89.0%, 87.4%, 75.8% and 71.0%; lipid, 97.5%, 94.0%, 92.1%, 75.8%, and 72.0%; fiber or chitin, 90.1%, 96.1%, 95.2%, 71.5%, and 69.3%; ash, 38.1%, 74.9%, 71.6%, 32.4%, and 30.8%; calcium, 17.1%, 20.3%, 20.9%, 13.2%, and 11.6%; phosphorus, 27.8%, 28.2%, 30.1%, 10.5%, and 9.7%; nitrogen-free extract 93.7%, 95.8%, 92.6%, 84.2%, and 82.7%; energy, 92.1%, 89.0%, 83.7%, 65.6%, and, 54.8%; and average amino acid, 91.2%, 89.6%, 87.1%, 76.2%, and 70.6%, respectively. These values were significantly affected by test ingredients (P<0.05). The results of the study suggest that the ADCs of protein are indicative of amino acid digestibility. However, variation in individual amino acid digestibility between feed ingredients means that determination of this parameter may allow more accurate and economical feed formulation.
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Tilapia are widely cultured in the tropical and subtropical regions of the world and constitute the third largest group of farmed finfish, only after carps and salmonids, with an annual growth rate of about 11.5%. Global production of farmed tilapia has increased more than three-fold since 1984, from 186,544 m.t. to 659,000 m.t., representing about 4.48% of total farmed finfish in 1995, with a value of US$925 million. Feeding represents over 50% of the operational costs of aquaculture. The shortage in world production of fish meal (the main conventional protein source), coupled with increased demand for fish meal in feeds for livestock and poultry is likely to reduce the dependence on fish meal as a single protein source in aquafeeds. Therefore, fish nutritionists have made several attempts to partially or totally replace fish meal with less expensive, locally available protein sources. The present review presents alternative dietary protein sources for tilapia, with emphasis on fishery by-products, terrestrial animal by-products, oilseed plants, aquatic plants, single cell proteins, grain legumes, plant protein concentrates and cereal by-products. The nutritive values, inclusion levels, constraints and economic evaluation of these sources are discussed.
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The use of lactic acid bacteria from human origins as a potential probiotic supplementation in aquaculture feed is now widely accepted. Here, we examined some of the properties and mechanisms of the action of Lactobacillus rhamnosus GG, originating from humans, on growth performance, gut mucosal immunity and humoral and cellular immune response in tilapia (Oreochromis niloticus). The results suggested that supplementation of L. rhamnosus gave an advantage in promoting the intestinal structure and the mucosal immunity of tilapia. Probiotic fish had a greater villous height in all parts of the intestines and, significantly, in the proximal and middle part. The population of intraepithelial lymphocytes was significantly higher in the probiotic group than in the control group in all parts of the intestines. The population of acidophilic granulocyte in the probiotic group was significantly higher at the proximal and distal parts when compared with the control group. The higher serum complement activity as well as the enhanced phagocytosis and killing ability of the head kidney leukocytes in the probiotic supplemented fish corresponded with the higher level of TNF alpha and IL-1 gene expression, suggesting that the induction of IL-1 and TNF alpha cytokines by L. rhamnosus served as an important regulator of gut associated immune systems.
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Fish farmed under high intensity aquaculture conditions are subjected to unnatural environments that may cause stress. Therefore awareness of how to maintain good health and welfare of farmed fish is important. For Atlantic salmon held in sea cages, water flow, dissolved oxygen (DO) levels and temperature will fluctuate over time and the fish can at times be exposed to detrimentally low DO levels and high temperatures. This experimental study investigates primary and secondary stress responses of Atlantic salmon post smolts to long-term exposure to reduced and fluctuating DO levels and high water temperatures, mimicking situations in the sea cages. Plasma cortisol levels and cortisol release to the water were assessed as indicators of the primary stress response and intestinal barrier integrity and physiological functions as indicators of secondary responses to changes in environmental conditions. Plasma cortisol levels were elevated in fish exposed to low (50% and 60% saturation) DO levels and low temperature (9°C), at days 9, 29 and 48. The intestinal barrier function, measured as electrical resistance (TER) and permeability of mannitol at the end of the experiment, were reduced at 50% DO, in both proximal and distal intestine. When low DO levels were combined with high temperature (16°C), plasma cortisol levels were elevated in the cyclic 1:5 h at 85%:50% DO group and fixed 50% DO group compared to the control (85% DO) group at day 10 but not at later time points. The intestinal barrier function was clearly disturbed in the 50% DO group; TER was reduced in both intestinal regions concomitant with increased paracellular permeability in the distal region. This study reveals that adverse environmental conditions (low water flow, low DO levels at low and high temperature), that can occur in sea cages, elicits primary and secondary stress responses in Atlantic salmon post smolts. The intestinal barrier function was significantly affected by prolonged hypoxic stress even when no primary stress response was observed. This suggests that intestinal barrier function is a good experimental marker for evaluation of chronic stress and that it can be a valuable tool to study the impact of various husbandry conditions on health and welfare of farmed Atlantic salmon.
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Lack of affordable feeds is one of the major constraints facing small-scale fish farmers in Tanzania. This study evaluated the suitability of moringa leaf meal (MLM), cassava leaf meal (CLM) and cassava root meal (CRM) as novel ingredients in Nile tilapia, Oreochromis niloticus diets. Each of the ingredients was processed in an attempt to remove the most significant antinutritional factor. A series of five experiments was conducted in a recirculation system using juvenile O. niloticus. The fish were fed isonitrogenous (30g 100g-1), isolipidic (10g 100g-1) and isoenergetic (18 kJ g-1) diets containing graded levels of the processed ingredients to their apparent appetite but not exceeding 10% of their body weight for a period of 8 weeks. Processing led to the removal of 0.3% of saponin from MLM and 60% and 90% of hydrogen cyanide from CLM and CRM respectively. The contents of other inherent antinutritional factors such as phenols, tannins and phytic acid were little affected. Processed MLM, CLM and CRM had 31.1/29.0/1.5g 100g-1 of crude protein, 5.9/10.2/2.4g 100g-1 of crude fibre and 20.1/19.7/15.8k Jg-1 of gross energy. The content of sulphur amino acids was higher in CLM (0.47%) than in MLM (0.23%). Digestibe protein and digestible energy was higher in MLM (25.71g 100g-1/15.44kJ g-1) than in CLM (12.71g 100-1/9.16kJ g-1). CRM had a digestible energy content of 13.5kJ g-1. Inclusion of either of the leaf meals, even at the lowest level of 15g 100g-1 of total dietary protein, led to a significant reduction in feed intake, growth and feed utilisation. Liver and small intestine did not show any histopathological changes which could be linked to dietary treatment. Conversely, cassava root meal could replace up to 75% of wheat meal in the diet without significantly affecting performance. The performance of leaf meals was marginally improved by a combination of blending and feeding stimulants, whereby a blend containing 1 part MLM and 2 parts CLM could provide up to 20g 100g-1 of dietary protein without significantly reducing performance. Biological and economic performance of practical diets containing 30-50g 100g-1 of dietary protein from moringa and cassava blends (LMB) with feeding stimulants was significantly lower than a fishmeal-meal based diet (FM) but comparable to a soybean meal-based diet (SBM). The suitability of MLM and CLM as novel protein sources in O. niloticus diets will depend on 1) improving reduction/removal of inherent antinutritional factors in MLM and CLM as well as improving digestibility of CLM. On the other hand, the suitability of CRM as a carbohydrate energy source will depend on the availability of cost effective protein sources due to its low protein content.
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The intestine is a complex multifunctional organ. In addition to digesting and absorbing feedstuffs, the intestine is critical for water and electrolyte balance, endocrine regulation of digestion and metabolism, and immunity. The intestines of carnivorous fish have evolved for processing a highly digestible, nutrient dense diet that is high in protein and low in carbohydrate. Correspondingly, abilities to digest protein are well developed, but carbohydrate digestion is low compared to omnivorous and herbivorous fish. Furthermore, the evolutionary stable diet is associated with a lack or reduced abilities to adaptively modulate digestive functions to match changes in diet composition. Despite similar selective pressures, intestinal structure is highly variable among carnivorous fish, reflecting phylogenetic diversity. Due to economic considerations, diets for cultured species often have varying proportions of plant-based ingredients. Although such feeds are effective for raising omnivorous and herbivorous species, they have provided limited success for carnivores, and this has been attributed to digestive limitations. Recent evidence of inflammatory responses to as yet unidentified components of some plants suggest involvement of the enteric immune system. Changes in temperature and salinity alter intestinal structure and functions, and therefore processing of dietary inputs. A relatively unknown component of the intestine involves the resident microbiota and its role in the health and disease of carnivoraus fish.
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This study was carried out to investigate the apparent digestibility coefficients (ADCs) value of protein, amino acid and energy and body amino acid composition of rainbow trout fed solvent extracted soybean meal (SBM) and full-fat soybean meal (FFS) partly replacing fish meal (FM) in diets. Five iso nitrogenous (average 50.36% crude protein) and energetic (4294 kcal/kg total energy) diets were designed in 5 groups in triplicates. Diet one as control group with 43% FM and 25% SBM, Diet 2 with 28% FM and 40% SBM, Diet 3 with 13% FM and 55% SBM, Diet 4 with 28% FM and 40% FFS, Diet 5 with 13% FM and 55% FFS. Diets were fed to trout fishes with 49 g initial body weight for 20 weeks at 8.8 +/- 0.45 degrees C. It was found that ADCs of energy, protein and most amino acids particularly methionine and lysine and fish body muscle lysine levels, significantly decreased by increasing the amount of FFS and SBM in diets (P<0.05). On the other hand, valine, isoleucine, threonine, methionine, phenylalanine, lysine and histidine showed a decreasing tendency with the increasing proportion of SBM in fish body composition. It was concluded that increasing the SBM and FFS percent replacing FM in trout fish diet, caused reducing protein, amino acid and energy digestibility, compared with the control diet. However, it can also be concluded that the replacement of SBM was more efficient than the replacement of FFS as regarding growth, ADCs of protein and essential amino acid contents of O. mykiss.
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Limited information is available on digestibility of nutrients in various practical ingredients used in diets for commercially important finfish species, such as hybrid striped bass. This information is especially needed for sunshine bass, Morone chrysops xM. saxatilis, to improve least-cost diet formulations and to allow effective substitution of feedstuffs. A study was conducted with large (867 g) sunshine bass to determine the apparent digestibility coefficients (ADCs) for moisture, protein, lipid, and organic matter (OM) in a variety of ingredients in floating, extrusion-processed, diets. The practical ingredients tested were menhaden (MEN) fish meal (FM), anchovy (ANCH) FM, pet-food grade poultry by-product meal, feed-grade poultry by-product meal, dehulled soybean meal (SBM), and distiller's dried grains with solubles (DDGS). Test diets consisted of a 70:30 mixture of reference diet to test ingredient with chromic oxide (1.0%) as the inert marker. Reference and test diet ingredients were mixed and extruded on a Wenger X85 single-screw extruder to produce floating pellets. The digestibility trials were conducted in twelve 1200-L circular tanks. Diets were randomly assigned to tanks of 30 sunshine bass and were fed once daily to satiation. Protein digestibility coefficients were significantly (P < 0.05) different among test ingredients and ranged from 86.42% for MEN to 64.94% for DDGS. Lipid ADCs were significantly different (P < 0.05) among test ingredients and ranged from 92.14% for MEN to 57.11% for SBM. OM ADCs were significantly different (P < 0.05) among test ingredients and ranged from 89.41% for MEN to 16.94% for DDGS. This information will assist in the formulation of more efficient, economical diets for sunshine bass.
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The gastrointestinal epithelial barrier protects the fish against toxic substances and microorganisms of the lumen. There are three functional barrier layers: (1) the extrinsic barrier consisting of secretions and commensal microorganisms, (2) the intrinsic barrier comprising epithelial cells and tight junctions between them, and (3) the immunological barrier. Together, they form a barrier efficient enough to keep animals healthy. The barrier is regulated according to need, varying in different environments and with life stage. However, stressors, such as physical and chemical environmental factors, suboptimal diet or starvation, pathogens, and acute stress, all can affect the barrier negatively. This can, in turn, lead to infections and diseases.
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This study evaluated the effects of replacing fish meal (FM) in practical diet for tilapia Oreochromis niloticus×O. aureus with different levels of soybean meal (SBM) on growth, digestive enzymes and liver transaminase activities. Five isonitrogenous (crude protein 300g/kg) and isoenergetic (gross energy 16kJ/g) practical diets were formulated by replacing 0 (the control), 25, 50, 75 and 100% of protein from fish meal with SBM. Each diet was randomly assigned to triplicate groups of 30 fish per aquarium (mean initial weight 4.0g). Fish were fed three times daily to apparent satiation for 8 weeks. The results showed that the growth was affected by dietary SBM level (P
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Numerous aspects of the wet acidic digestion procedure for the assay of chromic acid in a small amount of feed and excreta were examined to study the digestibility of feed by marine fishes; these examined were the spectral absorption curves of solutions prepared by the wet acid digestion of chromic oxide (Fig. 1), the stability of chromic acid solution obtained (Tables 1, 2), the effects of the amount of perchloric acid added (Table 2) and the wavelength to pre-pare the concentration-optical density curve (Fig. 2). The results of the present work showed that the following procedures were adequate for the study of digestibility. Weigh 50-100mg sample containing 1-3mg chromic oxide, wrap in a piece of filter paper and transfer to a dry 100ml Kjeldahl flask. Add 5ml of concentrated nitric acid in such a manner that it will wash down the particles adhered on the inside of the flask and allow to stand for a short period. Heat flask over a micro-electric heater which has the holes in the asbestos board covered so as to allow more heat to come in contact with the flasks. Allow the sample to digest until white precipitate is obtained (for about 20 minutes). When black particles adhere to the neck or side of the flask, wash them down by turning the flask 180°. Turn off the heater, cool the flask and 3ml perchloric acid to the digestion mixture and then reheat until green colour changes to yellow, orange or red. The reversal change in colour frequently occurs if the flasks are cooled just after the change in colour from green to yellow, because of the insufficient oxidation of the content. Therefore, the extension of digestion for 10 minutes is necessary after the colour change. Cool slightly and add about 50ml distilled water. Cool to room temperature and make up to 100ml in a volumetric flask with distilled water. Allow to stand for a few minutes to precipitate inor-ganic material. Transfer solution gently from the volumetric flask to a colorimetric tube, and read optical density at 350mμ against distilled water. The standard curve obtained by the wet acid digestion technique is expressed by the following equation;, Y=0.2089X+0.0032, where Y is the optical density at 350mμ, and X is the chromic oxide content of the sample (mg/100ml).
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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.
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The growth rate of Oreochromis aureus in relation to dissolved oxygen concentrations (2·63±0·12, 3·75±0·12, 6·51±0·13 ppm or 31·3, 44·6 and 77·5% saturation, respectively) was investigated. Three duplicated populations of 29 specimens (mean initial body weight ∼27·3 g) were reared in 100-litre tanks for 200 days under recirculated water conditions. Fish were offered an artificial diet three times per day, 6 days per week. The obtained results showed statistically significant final body weight differences (P < 0·05) between oxygen groups and actual differences regarding their specific growth rate and food conversion ratios. However, although mean body weight increased according to the dissolved oxygen concentration, the best food conversion ratio was shown by fish of the intermediate dissolved oxygen group. It is concluded that the lowest feeding cost involved in tilapia controlled mass production, could be achieved with relatively low dissolved oxygen concentration, under simple recirculated water system conditions.
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: Nile tilapia were exposed to severe hypoxic conditions. The respiratory frequency (RF) of the fish reached a maximum level at approximately 10 mmHg PO2 and decreased gradually thereafter. The fish sank to the bottom and subsequently their respiration began to stop. The hypoxic conditions increased the hematocrit value. As RF decreased, plasma cortisol and glucose levels climbed drastically. Just before respiratory arrest, the ATP and the total adenylate (TA) concentrations were significantly depressed in the liver, kidney and ordinary muscle but not in the heart or gill. As RF decreased, ATP and TA in both the liver and kidney decreased rapidly. Cytochrome oxidase activity increased significantly in the brain, heart, gill and ordinary muscle until respiratory frequency peaked. However, from the peak RF, this activity decreased in the liver and kidney. Lactic acid levels in both ordinary muscle and liver increased markedly when the fish sank. These results indicate that the stress response to hypoxic conditions is induced markedly with the decreased RF. It is also suggested that the decreased energy status in the liver and kidney of tilapia occurs at the same stage as the metabolic depression in the whole body, without increases in the aerobic and anaerobic metabolisms.
Article
The present study was performed to determine the effect of soybean meal (SBM) on the performance and gut histology of gilthead sea bream and European sea bass. Three isonitrogenous and isolipidic extruded diets (crude protein, 470 g kg−1 diet; crude fat, 200 g kg−1 diet) were formulated containing 0 (0 SBM), 180 (180 SBM) and 300 (300 SBM) g kg−1 diet SBM and tested on both species in two separate experiments. Fish at an initial average weight of around 18 g were randomly allocated to 800 L square tanks connected to a closed recirculating system. The trials lasted 80 days for sea bream and 89 days for sea bass. Fish were hand-fed to apparent satiation. Increasing the level of SBM had no significant effects on the specific growth rate, feed intake and feed conversion rate in both the species. In the sea bream distal intestine, lamina propria was moderately and diffusely expanded in some fish due to an increase in cell infiltration represented by mononuclear cells, this finding being more frequent in animals fed diet 300 SBM. No other morphological alterations in intestinal folds, enterocytes or other inflammation signs were noticed in the sea bream distal intestine of any group. No histological differences were found in sea bass in any experimental group.
Article
Apparent digestibility and growth experiments with three oil seed by-products, soybean meal, cottonseed meal, and sunflower seed meal, were conducted using tilapia (Oreochromis niloticus) with an initial average body weight of 93 ± 5 g and 64 ± 1 g, respectively. The diets were formulated on an isonitrogeneous and isoenergetic basis. During the experimental period the fish were fed 1% and 1.5% of their metabolic body weight (kg0.8) daily in the digestibility experiment and the growth experiment, respectively. Water temperature was maintained at 26.5 ± 1°C. Apparent digestibilities of the components and the diets were determined using an indirect method, i.e. with HCl-insoluble ash as an indicator. Faeces collection was carried out using a sedimentation technique.Results of the apparent digestibilities showed that the crude protein, crude fat, as well as the gross energy digestibilities of soybean meal (93.0%, 94.6%, and 77.2%, respectively), were better than those of cottonseed meal (79.4%, 83.2%, and 57.9%, respectively) and sunflower seed meal (89.8%, 82.9%, and 49.3%, respectively). With the exception of the crude protein digestibility, nutrient and gross energy digestibilities of the cottonseed meal were found to be better than that of sunflower seed meal.Growth experiment results indicated that soybean meal diet groups had inferior growth performance and feed conversion in comparison to the fishmeal control diet or the other test diets at an inclusion level of 32% of the digestible protein. Fish fed cottonseed meal diet and sunflower seed meal diet showed a relatively better, but not significantly different performance than did the fishmeal control diet. Supplementation diets with lysine and methionine did not enhance fish performance.
Article
The effect of complete replacement of fish meal by soybean meal (SBM) with the dietary L-lysine supplementation in prepared diet was studied in Nile tilapia fingerlings. Five isonitrogenous (33.2% crude protein) and isocaloric (4.8 kcal gross energy/g of diet) diets were formulated. Diet 1 was similar to a high quality commercial tilapia diet, containing 20% fish meal and 30% SBM. Diets 2–5 contained 55%, 54%, 53%, and 52% SBM and 0.5%, 1.0%, 1.5%, and 2.0% L-lysine supplementation, respectively. After 10 wk, there was a significant difference in the final individual weight, final body length (cm), weight gain (%), specific growth rate (SGR), feed conversion ratio (FCR), protein effkiency ratio (PER), and food intake among flsh groups (P≤ 0.05). The best bal individual weight, final individual length (cm), weight gain (%), specific growth rate, feed conversion ratio, protein efficiency ratio (PER), and food intake were recorded in fish fed diet 2, which contained 55% SBM and 0.5% L-lysine. There was a significant difference between it and diet 1 (control). Moisture in fish flesh was not significantly different (P > 0.05) among treatments and averaged 75.13%, while percentage protein was significantly dltrerent (P≤ 0.0% and the best result was achieved in flsh fed diet 2 and diet 1 (control). The highest values of digestibility coefficients of protein, fat and energy were recorded in groups of fish fed diet 2. These suggest that a diet with 55% SBM supplemented with 0.5% L-lysine can totally replace fish meal in a diet for Nile tilapia fingerlings, without adverse effect on fish performance.
Article
The present study on 120 fish (O. niloticus) were rearing in three ponds during 5 months (2008) at El-Kanater station. Pond I was untreated groups, ponds II and III were treated by vitamin C and 2 Cobalt chloride respectively. This conducted to demonstrate the effect of vitamin C and CoCl to illustrate the best treatment that gives the maximum growth rat and alleviation of pollution effects on some tissues (Kidney and Intestine). The results showed noticeable increase in growth rate of fish reared in Vitamin 2 C and CoCl than in untreated group. In addition to the some histopathological changes in kidney and intestine of fish reared at pond I (untreated group) due to the pollution of the Nile water. However, 2 improvement was observed in the sample collected from the ponds treated with vitamin C and CoCl .
Article
The development of a pathological condition in the distal intestine of Atlantic salmon, Salmo salar L., induced by dietary soybean meal, was studied in a 6-week feeding experiment. The fully developed condition, as observed after 3 weeks on the experimental diets, was characterized by: (1) a shortening of heights of the mucosal foldings; (2) a loss of the normal supranuclear vacuolization of the absorptive cells in the intestinal epithelium; (3) a widening of the central stroma within the mucosal foldings, with increased amounts of connective tissue; and (4) a profound infiltration of inflammatory cells in the lamina propria. The first signs of morphological changes were observed after 2 days on a diet containing a solvent extracted soybean meal, and within 7 days, all the above mentioned signs were observed. When the fish were subsequently transferred to a control diet, the mucosal folds were rebuilt from the base, resulting in an apparently functional epithelium after 3 weeks. Starved fish also exhibited characteristic changes of the mucosa, including a finely granular cytoplasm replacing the supranuclear vacuoles seen in the epithelial cells of normal fish. In addition, a pattern of irregularly spaced indentations developed in the epithelium of the simple folds. The condition induced by dietary soybean meal was classified as a no n-infectious subacute enteritis, and a pathogenesis involving immunological mechanisms is suggested.
Article
When juvenile turbot Scophthalmus maximus and sea bass Dicentrarchus labrax were fed to satiation, growth and food intake were depressed under hypoxia (3·2±0·3 and 4·5±0·2 mg O2 l-1). However, no significant difference in growth was observed between fishes maintained in hypoxia and fed to satiation and fishes reared in normoxia (7·4±0·3 mg O2 l-1) and fed restricted rations (same food intake of fishes at 3·2 mg O2 l-1). Routine oxygen consumption of fishes fed to satiation was higher in normoxia than in hypoxia due to the decrease in food intake in the latter. Of the physiological parameters measured, no significant changes were observed in the two species maintained in hypoxia. This study confirms the significant interaction between environmental oxygen concentrations, feeding and growth in fishes. Decrease in food intake could be an indirect mechanism by which prolonged hypoxia reduces growth in turbot and sea bass, and may be a way to reduce energy and thus oxygen demand.
Article
The use of plant-derived materials such as legume seeds, different types of oilseed cake, leaf meals, leaf protein concentrates, and root tuber meals as fish feed ingredients is limited by the presence of a wide variety of antinutritional substances. Important among these are protease inhibitors, phytates, glucosinolates, saponins tannins, lectins, oligosaccharides and non-starch polysaccharides, phytoestrogens, alkaloids, antigenic compounds, gossypols, cyanogens, mimosine, cyclopropenoid fatty acids, canavanine, antivitamins, and phorbol esters. The effects of these substances on finfish are reviewed. Evidently, little unanimity exists between the results of different studies as to the specific effects of antinutrients, since most studies have been conducted using an ingredient rich in one particular factor and the observed effects have been attributed to this factor without considering other antinutrients present in the ingredient, or interactions between them. Tentatively, protease inhibitors, phytates, antigenic compounds, and alkaloids, at levels usually present in fish diets containing commercially available plant-derived protein sources, are unlikely to affect fish growth performance. In contrast, glucosinolates, saponins, tannins, soluble non-starch polysaccharides, gossypol, and phorbol esters, are more important from a practical point of view. The effectiveness of common processing techniques such as dry and wet heating, solvent extraction and enzyme treatment in removing the deleterious effects of antinutrients from feed materials is discussed. More insights into the nutritional, physiological and ecological effects of antinutrients on fish need to be accumulated through studies using purified individual antinutrients and their mixtures in proportions similar to those in alternative nutritional sources in fish feeds. Such studies would provide data useful for designing optimum inclusion levels of plant-derived materials and treatment methods that would neutralise the negative effects of the antinutritional factors.
Article
Effects of moderate hypoxia and oscillating oxygen conditions on growth of European sea bass (Dicentrarchus labrax L.) were investigated. Groups of four to six sea bass (initial weights 40–90 g) were exposed to one of three oxygen regimes (40% air saturation; oscillations between 40–86% with a period of 770 min; 86% as a control) at 22°C and a salinity of 37 for 1 month. All fish survived and gained weight, but relative to the controls, the sea bass exposed to hypoxic conditions consumed significantly less food, exhibited a reduced growth, and had a lower condition factor. Oscillating groups were intermediate, and not statistically distinguishable from either normoxic or hypoxic treatments. Feed conversion efficiency and variation in body size were not significantly affected by oxygen conditions. Growth was correlated with feed intake, suggesting that reduced growth under moderate hypoxic or oscillating oxygen conditions is primarily due to reduced appetite and not a consequence of a decrease in feed conversion efficiency.
Article
Barrier and immunological functions of the gut in fish are discussed in this chapter. The gut is known to be an important site often targeted by invading pathogenic microbes, and constant exposure to aquatic microbes requires defense mechanisms to be present in the gut that act rapidly to limit infection. These include many physical, chemical, and cellular components that prevent infection by presenting a barrier to invasion; however, innate and adaptive immune responses can be initiated in the gastrointestinal tract as part of a mucosal immune response. The mucosal immune system in fish includes not only the gut but also mucosal tissues associated with the gills and skin. In mammals, this system is well developed and exposure to pathogens or immunization with antigens delivered to one mucosal site results in antigen-specific antibody production at other mucosal sites. Fish are capable of mounting similar responses via the gut and skin, but the mucosal system in fish functions in a more primitive manner than in mammals. Protective functions of the gut of fish involve inhibition of colonization by microbes at mucosal sites, rapid elimination of pathogens through innate responses, and development of adaptive immunity following antigen uptake and processing.
Article
Feed intake and satiation in fish are regulated by a number of factors, of which dissolved oxygen concentration (DO) is important. Since fish take up oxygen through the limited gill surface area, all processes that need energy, including food processing, depend on their maximum oxygen uptake capacity. Maximum oxygen uptake capacity relative to body weight in bigger fish is smaller than in smaller fish because the gill surface area is allometrically related to body weight. In this study, effects of DO concentration and body weight on maximum feed intake, growth and hematological parameters of Nile tilapia (Oreochromis niloticus) were investigated. Two weight classes of fish (21 g and 147 g) were used. For each class, six tanks were employed of which half were exposed to one of two DO levels (about 3.0 mg/L and 5.6 mg/L). Fish were fed to apparent satiation twice per day with a commercial diet. The results showed that (1) feed intake and growth of the fish at high DO level were significantly higher than at low DO level (P < 0.01), (2) relative feed intake and growth of small fish were significantly higher than of big fish (P < 0.001), and (3) fish at low DO level made no hematological adjustments (P ≥ 0.5). Data suggest that (1) the limitation of the gill surface area results in lower feed intake and growth of fish at low DO concentration than at high DO concentration and (2) the allometric relationship between the gill surface area and body weight results in lower relative feed intake, which in turn results in lower relative growth in big fish than in small fish.
Article
Low dissolved oxygen environments occur in a wide range of aquatic systems, and vary in temporal frequency, seasonality, and persistence. While there have always been naturally occurring low dissolved oxygen habitats, anthropogenic activities related primarily to organic and nutrient enrichment have led to increases in hypoxia and anoxia in both freshwater and marine systems. Lakes and coastal areas with seasonal stratification tend to be highly sensitive to the consequences of anthropogenic nutrient enrichment. Many systems that are currently hypoxic were not reported to have low dissolved oxygen concentrations when first studied. The rapid rise in the number of coastal hypoxic systems lagged about 20 years behind the increased use of industrial fertilizer. The future status of hypoxia and its consequences for fishes will depend on a combination of climate change (primarily from warming, and altered patterns for wind, currents, and precipitation) and land use change (primarily from expanded agriculture and nutrient loadings). If in the next 50 years humans continue to modify and degrade coastal systems as in previous years, human population pressure will likely be the main driving factor in spreading of coastal dead zones and climate change factors will be secondary. Climate forcing, however, will tend to make systems more susceptible to development of hypoxia through direct effects on stratification, solubility of oxygen, metabolism, and mineralization rates, particularly in lakes and semienclosed coastal areas.
Article
The morphology of the proximal and distal intestine of Atlantic salmon (Salmo salar) was studied after prolonged feeding with diets containing full-fat soybean meal (FFSB) or soybean protein concentrate (SBPC) and compared with fish fed a standard herring meal (HM) diet. To avoid possible changes due to decreased food intake, dietary inclusions of FFSB and SBPC were chosen at such levels that weight gain, and protein and lipid digestibility values were similar for all three groups. The proximal intestine showed no differences among the groups, except for an increased number of goblet cells in the fish fed SBPC. In the distal intestine, the SBPC group showed no abnormalities and was identical to the HM group. In the FFSB group, the epithelium had an increased number of goblet cells and a marked decrease or even absence of absorptive vacuoles. The microvilli of the enterocytes were shortened, with increased microvillar vesicle formation.These changes may be due to the presence of antinutritional factors in the FFSB diet. The possible role of the various antinutritional factors in soybeans for the development of the intestinal lesions, and their effect on growth and performance are discussed.
Article
Two experiments were conducted in order to investigate the effect of dietary mannan oligosaccharides (MOS) on gilthead sea bream (Sparus aurata). Experiment I was designed to assess the effect of dietary MOS (0%, 0.2% and 0.4%) on fish fed diets containing fishmeal (FM) as the only protein source. Experiment II was designed to assess the effect of MOS (0% and 0.4%) on fish fed soybean meal (SBM) as a partial replacement of FM (SBM inclusion 31% of diet). After 9 weeks feeding on the experimental diets growth parameters, body composition, liver and intestinal histology and intestinal microbial diversity were assessed. The results showed that mean final weight, specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) remained unaffected by MOS supplementation of fish fed FM or SBM diets.
Article
The effects of hypoxia on growth, feed efficiency, nitrogen excretion, oxygen consumption and metabolism of juvenile turbot (120 g) were studied in a 45-day experiment carried out in sea water at 17.0±0.5°C and 34.5 ppt salinity. Fish were fed to satiation at O2-concentrations of 3.5±0.3, 5.0±0.3 mg l−1 (hypoxia) and 7.2±0.3 mg l−1 (normoxia). Both feed intake (FI) and growth were significantly lower under hypoxia than under normoxia, with no significant differences being observed between 3.5 and 5.0 mg O2 l−1. During the first 2 weeks of the experiment, FI was halved under hypoxic conditions, and there were large differences among treatments in feed conversion ratio (FCR), i.e., it was 3.2, 1.5, and 0.9 in turbot exposed to 3.5, 5.0, and 7.2 mg O2 l−1, respectively. Thereafter, FCR was not significantly affected by O2-concentration. Nitrogen excretion and oxygen consumption of feeding fish were significantly higher under normoxia than under hypoxia, but following 7 days of feed deprivation oxygen consumption was similar under normoxia and hypoxia. Plasma osmolarity, ionic balance, and acid-base status were not affected by the two hypoxic conditions tested. Overall, our results indicate that turbot have some capacity to adapt to relatively low ambient O2-concentrations.
Article
The gastrointestinal (GI) tract has many important biological functions. One is to serve as a barrier between the fish and the external environment. A decreased physical barrier function of the intestine may lead to increased inflow of luminal content and subsequent activation of the intestinal mucosal immune system. This activation is governed by the ability of various compounds to induce cytokine release and immune cell activity, leading to an immune response. In mammals, the impact of stress on the intestinal barrier is well documented and results in increased intestinal permeability and thus increased stimulation of the mucosal immune system. Fish reared in sea cages may at times be exposed to unfavourable environmental conditions leading to chronic stress and disturbed intestinal integrity. This change in permeability may increase the exposure of the mucosal immune system to activating compounds. In the present study, the effect of a prolonged stress on the intestinal mucosal immune system of fish is therefore addressed. Atlantic salmon were exposed to low levels (50%) of dissolved oxygen (DO) for 6-7 weeks in consecutive experiments performed at 8 and 16 °C. Immune parameters were assessed in terms of mRNA expression of the key cytokines, interleukin-1β (IL-1β), IL-8, IL-10, interferon-γ (IFNγ) and transforming growth factor-β (TGFβ) as well as the immune regulatory inhibitor of nuclear factor κB (IκB). In the experiment at 8 °C also mucosal neutrophil infiltration was monitored. Subjecting the fish to low DO levels at 8 °C resulted in an increased mucosal neutrophil infiltration together with a down-regulation of IκB. At the higher temperature, 16 °C, low DO levels created decreased expression of the pro-inflammatory cytokine IL-1β in both intestinal regions as well as an increased expression of IL-10 in the proximal intestine. These results suggest that husbandry conditions in sea cages with DO levels as low as 50% clearly affects the intestinal mucosal immune system and results in a chronic inflammation. Moreover, the effects of low DO levels on the immune factors examined were more pronounced in the 16 °C experiment suggesting additive effects of high temperatures.
Article
This study evaluates the effect of temperature on the development of intestinal disorders when Atlantic salmon are fed soybean meal (SBM). In this study 20% of the dietary fishmeal was replaced by solvent-extracted Hipro SBM. Atlantic salmon reared at two different water temperatures (8¿°C and 12¿°C), were fed a control diet and an experimental diet for 20¿days. Samples were taken at days 7 and 20. The extent of the morphological changes was assessed using a semi-quantitative scoring system developed for this purpose. The study demonstrates that enteritis is affected by temperature. The intestinal disorders were more severe in fish reared at 12¿°C compared with those reared at 8¿°C. It can be concluded from this study that temperature changes the speed but not the type of SBM-induced enteritis expressed as a delay on the response when Atlantic salmon are kept at lower temperatures.
Article
The purpose of these studies was to determine the effects of diets containing water/alcohol extracts from soybean meal (SBM) on growth and performance, intestinal histology and specific and nonspecific immune parameters of juvenile rainbow trout. The first study evaluated seven experimental diets containing SBM, SBM after extraction, soy protein concentrate (SPC), SPC after extraction, SBM saponin extract, SBM flavonoid extract and Quillaja saponin (0.171%). A casein-gelatin based diet served as a control diet. The second study evaluated SBM, SBM after extraction, SBM carbohydrates, SBM flavonoid extract, SBM saponins, SBM lipids, and negative control (containing 50% of casein-gelatin). Diets were formulated to have one half of the casein-gelatin replaced by soybean protein or supplemented with methanol/water extracts in amounts equal to the amounts found in 50% protein replacement. All female rainbow trout (Troutlodge, Inc., Sumner, WA) were subjected to feeding experiments beginning at first exogenous feeding. After initial feeding trials fish were maintained on experimental diets until vaccination. In the first study one half of the fish in each tank were vaccinated at 13 weeks by intraperitoneal injection of 0.1 ml Furogen vaccine (AquaHealth Ltd.; aluminum phosphate adjuvanted Aeromonas salmonicida bacterin). The other fish in each tank were injected with phosphate buffered saline (PBS) as a control. Each fish was fin clipped to identify control and vaccinated fish. In the second study one half of the fish in each tank were vaccinated after reaching an approximate mean individual weight of 5 grams (different chronological ages) with Furogen Dip vaccine (AquaHealth Ltd.; formalin inactivated Aeromonas salmonicida bacterin). Fish in the first study were sampled 2 and 4 weeks after vaccination for specific humoral antibody responses and non-specific mucosal immune responses. Fish in the second study were sampled 2, 4 and 7 weeks after vaccination to determine specific antibody responses in plasma and in mucus. Samples of the posterior mid-intestine were taken prior to vaccination in the second study to determine histological changes due to dietary treatment. Fish fed diets containing SBM, SBM after extraction, SPC, SPC after extraction and SBM carbohydrates all exhibited lower growth than the control diet. Fish fed the saponin, lipid and flavonoid fractions performed similarly as control. Fish fed soybean saponins had higher specific plasma antibody levels after intraperitoneal vaccination but not after immersion vaccination. Feeding fish soybean saponins did not result in histological changes in the posterior intestine resembling those in fish with soybean induced posterior enteritis. It is concluded that purified soybean saponins, when included in the diet in an amount equivalent to the amount in 50% protein replacement, do not result in reduced growth and performance or pathological changes in the posterior intestine consistent with soybean induced posterior enteritis. Additionally, orally administered soybean saponins can augment the specific immune response following intraperitoneal vaccination. Scope and method of study. This study describes the environmental and cultural impacts of the four United States Army Corps of Engineer dams built on Arkansas' White River. Focusing especially on the establishment of the tailwater trout fisheries created below these bottom-release dams, the study examines how management of the dams and trout fisheries evolved over time as sport fishing increased in economic and recreational importance. Information for this study was collected from various historical documents, personal interviews, government reports, and the Arkansas Game and Fish Commission's Trout Program archives. Findings and conclusions. Beginning in about 1870 and continuing into the 1930s the White River was a popular warm-water sport fishery and float fishing destination that assisted in the development of Ozark tourism. With the completion of Norfork Dam in 1944, and continuing with the completion of Bull Shoals, Greers Ferry, and Beaver dams, the river became a series of large reservoirs and cold-water tailwaters. Exotic trout stocked into these tailwaters created a lucrative commercial trout angling industry that eventually eclipsed in value the dams authorized purposes of flood control and hydropower production. These tailwater trout fisheries eventually became world renowned among trout anglers, and important to the local and state economy. Each tailwater now supports a distinct linear trout angling region delineated by numerous resorts, outfitters, and fly-fishing shops in a region formerly devoid of trout. Since no water storage was allocated for recreation, state fisheries managers, angling interests, and the federal agencies responsible for hydropower production and flood control struggle to balance the needs of the downstream fishery and recreation with the Congressionally authorized purposes, especially in relation to the amount of instream flow. Two thesis bound in one volume. Thesis (Ph. D.) -- Ohio State University, 2005. Thesis (Ph. D.) -- Oklahoma State University, 2005. Includes bibliographical references. Photocopy.
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When juvenile turbot Scophthulmus maximus and sea bass Dicentrarchus labrax were fed to satiation, growth and food intake were depressed under hypoxia (3.2 +/- 0.3 and 4.5 +/- 0.2 mg O-2 l(-1)). However, no significant difference in growth was observed between fishes maintained in hypoxia and fed to satiation and fishes reared in normoxia (7.4 +/- 0.3 mg O-2 l(-1)) and fed restricted rations (same food intake of fishes at 3.2 mg O-2 l(-1)). Routine oxygen consumption of fishes fed to satiation was higher in normoxia than in hypoxia due to the decrease in food intake in the latter. Of the physiological parameters measured, no significant changes were observed in the two species maintained in hypoxia. This study confirms the significant interaction between environmental oxygen concentrations, feeding and growth in fishes. Decrease in food intake could be an indirect mechanism by which prolonged hypoxia reduces growth in turbot and sea bass, and may be a way to reduce energy and thus oxygen demand.
Article
Abstract Soybean meal (SBM) induces enteritis in the distal intestine of Atlantic salmon. The present study assesses the effects of SBM concentrations on the kinetics of the enteritis process. Fish of 300 g, kept at 12 degrees C, were fed diets with different SBM inclusions: 0%, 10% and 20% SBM for 57 days. Samples of the distal intestine of five fish per treatment were taken for histological and electron microscopical analysis. A semi-quantitative scoring system was used to assess the degree of the morphological changes induced by SBM feeding in the distal intestinal epithelium. The first signs of enteritis appeared earlier in the salmon fed the 20SBM diet than in those fed the 10SBM diet. Thereafter, the condition increased steadily, displaying no signs of recovery. Furthermore, at the lower concentration, the process marking the onset of enteritis began more gradually than at the higher concentration and it displayed a tendency to stabilize after 13-20 days of continuous feeding. Electron microscopy indicated that the endocytosis process was hampered at day 3 of 20SBM and at 7 days of 10SBM. Furthermore, a strong reduction of microvilli was already evident after 7 days of 20SBM feeding, thus indicating a decreased uptake capacity of the distal enterocytes. In addition, transformation and migration of eosinophilic granulocytes was observed, which, in combination with the lysozyme C immunoreactivity supports their protective role during the inflammatory process in the distal gut of Atlantic salmon. It can be concluded that the severity of enteritis and its kinetics are concentration-dependent, showing no signs of recovery during feeding with diets containing SBM.
Article
The development of soybean meal (SBM) induced enteritis in the hindgut of the omnivorous common carp (Cyprinus carpio L.). The developed condition was assessed when carp, continuously fed on animal protein, were transferred to a diet in which 20% of the protein was replaced by SBM. After week 1, most of the inflammation parameters were already present, but at week 3, a strong aggravation of the condition was observed which included a shortening of the mucosal folds, the disappearance of the supranuclear vacuoles, an increased number of goblet cells, a thickened lamina propria and sub-epithelial mucosa with increased numbers of basophilic granulocytes as well as a decreased uptake capacity of enterocytes (impaired endocytosis and microvilli). Contrary to previous observations made with respect to Atlantic salmon, common carp start to recover from the fourth to the fifth week after switching to SBM feeding. At this stage, the supranuclear vacuoles refill and most of the parameters revert to basal levels. During the enteritis process, a real-time quantitative PCR analysis was conducted to measure the expression of inflammatory and anti-inflammatory cytokine genes in the isolated intraepithelial lymphocytes (IEL). The pro-inflammatory interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha1 (TNF-alpha1) genes were up-regulated during the inflammation process while the anti-inflammatory interleukin 10 (IL-10) was down-regulated after an initial up-regulation at week 1. Transforming growth factor beta (TGF-beta) expression showed an up-regulation from week 3 onwards despite the high Ct value and the low primer efficiency shown. This study confirms the contribution of IEL (mainly T-like cells) and basophils in the enteritis process. In addition, the results show a clear involvement of up- and down-regulated cytokine genes in both the onset and recovery of the SBM-induced enteritis in the hindgut of carp.