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Empirical growth models have widespread application in the field of aquaculture. These models allow estimates of harvest size and waste outputs in addition to nutrient and feed requirements. In an effort to increase the ability to predict shrimp growth, the specific growth rate (SGR) and thermal‐unit growth coefficient (TGC) models were fitted to 15 datasets encompassing growth of Pacific whiteleg shrimp (Litopenaeus vannamei). Shrimp were reared under commercial conditions in Southeast Asia with weights ranging from 0.01 g to 34 g. Growth rates were regressed against body weights to identify changes in growth pattern across life stages. Analysis identified two distinct patterns of growth, with a break point between stanzas at 7.5 g. The body weight exponent of the TGC model, traditionally assumed to be (1 − b) = 1/3, was solved for iteratively in each identified growth stanza in an effort to improve the goodness of fit of the TGC model. Average body weight exponents in the first and second stanzas were 0.416 and 0.952 respectively. Projected growth trajectories using these exponents resulted in significantly better fits in comparison to the traditional TGC and the SGR on the basis of statistical measures of goodness of fit.

This study describes the process of developing an enzymatic pretreatment to improvethe nutritional value of feather meal (FeM). In a first experiment, a full factorial design was used toexamine the effects of various incubation conditions on the solubilization of nitrogen in FeM. Weincubated FeM for 3 h with various levels of a commercial alkaline serine protease (Savinase®16L), sodium sulphite (Na2SO3), and digestion buffer. A Savinase® 16L level of 3% (%FeM v/w),Na2SO3 level of 3% (%FeM w/w), and digestion buffer level of 500% (%FeM w/w) were identifiedas the optimal conditions. Under these optimal conditions, 45% of the nitrogen in FeM wassolubilized. In a second experiment, we evaluated the effect of more economically sustainableincubation conditions on the in vitro digestibility of protein (pepsin-HCl digestibility andmultistep protein evaluation) in FeM. Two FeMs were incubated with 0.5% Savinase® 16L (%FeMv/w), 2% Na2SO3 (%FeM w/w), and 200% buffer (%FeM w/w) for 24 h. The pretreatment improvedpepsin-HCl digestibility by 7%–16% and the total tract degradable protein content by 14%–50%.Accordingly, this novel pretreatment could be applied in the animal feed industry to improve thenutritional value of FeM.

A digestibility trial was carried to assess the apparent digestibility coefficient (ADC) of crude protein (CP) and amino acids (AA) in two feather meals (FeM) of different origin (FeM1 and FeM2) and in their enzymatically pre‐treated ingredient stream (PTFeM1 and PTFeM2) in rainbow trout. The ADC of CP was 11%–17% higher (p 0.05) of ADC of CP among FeMs and among PTFeMs. The FT‐Raman analysis showed a reduction in concentration and conformational stability of disulphide bonds in the PTFeMs when compared to their FeM counterparts. Moreover, important discrepancies in disulphide concentration were observed between FeMs and between PTFeMs. These observations suggest that the ADC of CP in FeM is not only governed by disulphide bond content and other variables should be considered. Higher concentrations of the cross‐linked amino acids (CLAA) lanthionine, lysinoalanine and β‐aminoalanine were measured in FeM1 and PTFeM1 as compared to FeM2 and PTFeM2 respectively. Previous studies have suggested inverse relationships between CLAAs and the digestibility as well as bioavailability of AAs in feed ingredients. A previous study conducted in our laboratory showed a lower (p

The efficiency of utilization and thus requirement of essential amino acids (EAAs) of fish are known to be influenced by a number of dietary and biological factors. Very little is known about the effect of body weight on the utilization efficiency of EAAs. A 3 × 3 factorial experiment was carried out to investigate the effect of body weight on lysine utilization efficiency of Nile tilapia (Oreochromis niloticus). Three diets containing graded levels of lysine at 0.9, 1.1 and 1.3% were fed to groups of fish of three weight classes (small, S; medium, M; and large, L) with initial mean body weights of 10, 58, and 248 g. The fish were fed to apparent satiation over a 12-week period at 28 °C in a recirculation system. The results showed that body weight classes significantly affected growth, feed efficiency, whole body composition, and retention efficiencies of protein, energy and lysine. Retention efficiencies of protein, energy and lysine were different across weight classes: lowest in large fish and highest in small fish. Marginal lysine utilization efficiency (lysine gain/lysine intake) was assessed to be 68%, 63% and 47% for S, M and L fish, respectively. It appears that the marginal lysine utilization efficiencies remained relatively high in fish of small and medium sizes but decreased in fish of large size. The effect of body weight on marginal lysine utilization efficiencies could be represented by a linear equation: marginal lysine utilization efficiency (%) = 69–0.078 × body weight (g) (r2 = 0.9997). The efficiencies of lysine utilization for protein gain also followed a similar pattern across body weight classes, with the lowest efficiency at the highest body weight. Results from this study contribute to a better understanding of requirement and utilization of lysine in fish. Results from this study could also be useful for the development of factorial models of amino acid requirement and the formulation of cost-effective diets for Nile tilapia across life stages.

Increasing evidence suggests that variability in hepatic glucuronidation is a critical determinant of mammalian species-specific sensitivity to the Fusarium mycotoxin deoxynivalenol (DON). Concurrently, ongoing work regarding the effects of DON on fish has led to broad classifications concerning species-specific sensitivity (e.g. rainbow trout are highly sensitive to DON and channel catfish are highly tolerant to DON). This study was designed to determine if sensitivity to DON in fish is related to inherent differences in UDP-glucuronosyltransferase (UDPGT) activity and to evaluate if increased dietary digestible starch content could be an effective strategy to increase glucuronidation capacity. Rainbow trout or Nile tilapia (initial average body weight = 21.9 and 8.1 g/fish, respectively) were fed two series (12 or 24% digestible starch) of three diets containing graded levels of naturally occurring DON (0.1, 0.7 and 1.3 ppm) for 10 weeks. Significant linear decreases in weight gain, thermal-unit growth coefficient (TGC, P ≤ .05), feed efficiency (P .05) with the exception of a quadratic increase in NRE (P .05, DON × digestible starch). A significant quadratic decrease (P ≤ .05) in UDPGT activity was associated with increasing levels of DON in rainbow trout fed the diet containing 12% digestible starch, whereas trout and tilapia fed the diet containing 24% digestible starch experienced significant quadratic or linear increases (P ≤ .05) in UDPGT activity, respectively. However, UDPGT activity was approximately 10-fold higher in rainbow trout than in Nile tilapia. This suggests that UDPGT activity is not responsible for the observed species-specific sensitivity to DON or it is not an appropriate biomarker of DON glucuronidation. A significantly higher relative fold expression of CYP1A in tilapia compared to trout (P = .0001) may offer potential opportunity for future study. We demonstrate for the first time that Nile tilapia are unaffected by practically relevant levels of DON which are detrimental to rainbow trout. This study also extends the current knowledge of DON metabolism and represents an important contribution to the development of efficacious nutritional mycotoxin mitigation strategies.

It has been previously established that rainbow trout are extremely sensitive to the ubiquitous Fusarium mycotoxin deoxynivalenol (DON) however, the contribution of co-occurring mycotoxins and/or their potential interactions with DON have not been discounted. Concurrently, there have been few systematic efforts to characterize the pathological basis of the sensitivity of rainbow trout to DON. This study was conducted to investigate these outstanding issues. Triplicate groups of rainbow trout (initial average body weight = 50.3 g/fish) were fed eight diets containing graded levels of purified DON (0, 0.7, 1.4 and 2.1 ppm) or DON from naturally contaminated corn (0, 2.1, 4.1 and 5.9 ppm) for eight weeks. Fish experienced significant linear decreases in weight gain (P .025) in the above mentioned parameters between fish fed the diets contaminated with the same level of purified or naturally occurring DON (2.1 ppm). In general, bi-weekly sampling (6 fish/treatment/sampling) revealed significant linear or quadratic increases in dead (apoptotic/necrotic) cells in the pyloric caeca and significant linear or quadratic decreases in mitotic cells in the pyloric caeca and liver with increasing dietary levels of purified DON or DON from naturally contaminated corn without any distinct histopathological abnormalities (i.e. lesions). These cellular changes are in agreement with the known ability of DON to activate mitogen-activated protein kinases (MAPKs) indicating that the mechanism of action of DON in rainbow trout is consistent with that described in other species. Comparison of the response of fish fed the diet containing 2.1 ppm purified DON and 2.1 ppm DON from naturally contaminated corn suggested that decreased growth performance and nutrient utilization efficiency of rainbow trout exposed to grains naturally contaminated with Fusarium mycotoxins was most probably associated mainly with DON however, continued research involving multiple levels of purified and naturally occurring DON is necessary to verify this finding. Biomin B.R.A.I.N. grant Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) info:eu-repo/semantics/publishedVersion

High temperature is a powerful stressor for fish living in natural and artificial environments, especially for cold water species. Understanding the impact of thermal stress on physiological processes of fish is crucial for better cultivation and fisheries management. However, the metabolic mechanism of cold water fish to thermal stress is still not completely clear. In this study, a NMR-based metabonomic strategy in combination with high-throughput RNA-Seq was employed to investigate global metabolic changes of plasma and liver in a typical cold water fish species lenok (Brachymystax lenok) subjected to a sub-lethal high temperature. Our results showed that thermal stress caused multiple dynamic metabolic alterations of the lenok with prolonged stress, including repression of energy metabolism, shifts in lipid metabolism, alterations in amino acid metabolism, changes in choline and nucleotide metabolisms. Specifically, thermal stress induced an activation of glutamate metabolism, indicating that glutamate could be an important biomarker associated with thermal stress. Evidence from Hsp 70 gene expression, blood biochemistry and histology confirmed that high temperature exposure had negative effects on health of the lenok. These findings imply that thermal stress has a severe adverse effect on fish health and demonstrate that the integrated analyses combining NMR-based metabonomics and transcriptome strategy is a powerful approach to enhance our understanding of metabolic mechanisms of fish to thermal stress.

Deoxynivalenol, a type B trichothecene mycotoxin produced by Fusarium species of fungi, is a ubiquitious contaminant of cereal grains worldwide. Chronic, low dose consumption of feeds contaminated with DON is associated with a wide range of symptoms in terrestrial and aquatic species including decreased feed intake and feed refusal, reduced weight gain, and altered nutritional efficiency. Acute, high dose exposure to DON may be associated with more severe symptoms such as vomiting, diarrhea, intestinal inflammation and gastrointestinal hemorrhage. The toxicity of DON is partly related to its ability to disrupt eukaryotic protein synthesis via binding to the peptidyl transferase site of the ribosome. Moreover, DON exerts its effects at the cellular level by activating mitogen activated protein kinases (MAPK) through a process known as the ribotoxic stress response (RSR). The outcome of DON-associated MAPK activation is dose and duration dependent; acute low dose exposure results in immunostimulation characterized by the upregulation of cytokines, chemokines and other proinflammatory-related proteins, whereas longer term exposure to higher doses generally results in apoptosis, cell cycle arrest, and immunosuppression. The order of decreasing sensitivity to DON is considered to be: swine > rats > mice > poultry ≈ ruminants. However, studies conducted within the past 10 years have demonstrated that some species of fish, such as rainbow trout, are highly sensitive to DON. The aims of this review are to explore the effects of DON on terrestrial and aquatic species as well as its mechanisms of action, metabolism, and interaction with other Fusarium mycotoxins. Notably, a considerable emphasis is placed on reviewing the effects of DON on different species of fish.

Hepatic glucuronidation represents an important phase II biotransformation reaction in both mammals and fish. The kinetic characteristics of uridine 5′-diphosphate (UDP) glucuronosyltransferases (UDPGTs) in rainbow trout liver microsomes were examined using p-nitrophenol (p-NP) as an aglycone and UDP-glucuronic acid (UDPGA) as a glucuronyl donor according to an existing protocol. The kinetic data obtained with varying concentrations of p-NP best fit the Hill equation and UDPGT activity was successfully induced following an i.p. injection of β-naphthoflavone (β-NF). The assay was subsequently adapted to a microplate method for determination of UDPGT activity in microsomal samples obtained from rainbow trout as well as Nile tilapia. In contrast to rainbow trout, UDPGT activity of Nile tilapia was best described by Michaelis-Menten kinetics. Based on the linearity of p-NP glucuronide formation, a p-NP concentration of 0.60 mM and a UDPGA concentration of 6.89 mM were determined to be suitable for assaying UDPGT activity in samples from rainbow trout and Nile tilapia. The microplate method offers several advantages over the historical assay; most notably it enables the observation of successive kinetics which ensures that enzyme activity is calculated in the most linear (initial) rate of the reaction. It also provides practical advantages in terms of ease-of-use and efficiency. This may be relevant to researchers investigating exposure of wild or farmed fish to environmental or feed-borne contaminants which are substrates of UDPGTs.

Aquaculture nutritional models play a vital role in the management of fish culture operations. This study reported a combined nutritional model constructed based on the data from several fish farms and published studies in order to predict the growth, feed requirement and waste output of gibel carp (Carassius auratus gibelio) and the web-based model service platform. This combined model comprised a growth model, a feed requirement model and waste (nitrogen and phosphorus) output model. The performance of different growth models and the growth trajectory of gibel carp were analyzed based on growth data obtained from two fish farms in Jingzhou, Ningbo (China) and published studies. The least squares method was used to optimize the growth coefficient within each growth stanza and to choose the best fit of growth model, which was the thermal-unit growth coefficient (TGC) model. Three growth stanzas of gibel carp in its life cycle were found by using TGC model, which were from first-feeding (1 g) to 13.5 g (Stanza 1); from 13.3 to 175.5 g (Stanza 2); and > 175.5 g (Stanza 3). Feed requirement of fish in different growth stages were determined by digestible energy requirement (DEreq), estimated based on the summary of recovered energy (RE), basal metabolism (HeE), heat increment of feeding (HiE), and urinary and branchial excretion (UE + ZE). Nutrient mass balance method was used to estimate waste output when the different growth stages of gibel carp was fed with different diets. The combined model was developed as a web-based service which could be obtained freely online. The design and implementation of the program which included three layers, i.e., front user side, application layer and data storage, were also reported in the current study. The user interface, functionalities of the application layer and database design were outlined. The service could be accessed by any browser and mobile device, providing a convenient tool for fishery management for farmers, farm managers and researchers in academia. The validation of the predicted body weight and feed conversion rate (FCR) showed that the current combined model has a great reference value in estimating the growth, feed requirement and waste discharge in gibel carp farms. The web-based model service could be an effective tool for benchmarking the growth performance, providing differentiated production, reducing feed waste, increasing economic benefits, and evaluating aquaculture pollution in different gibel carp culture operations.

The effects of graded levels (0–20% total dietary inclusion) of commercial, solvent-extracted soybean meal (SBM) and expeller sunflower meal (SFM) were investigated on growth, nutrient utilization, and pro-inflammatory gene expression in the distal intestine and spleen of two commercial Canadian strains (Strain 1 and Strain 2) of Arctic charr. Five experimental diets with increasing inclusion of SBM or SFM were fed for 84 days to two Canadian strains of Arctic charr (initial body weight = 9 g/fish). Feeding these diets resulted in no differences in growth rate (measured as final weight or thermal-unit growth coefficient, TGC) in the two strains. Increased inclusion level of plant proteins negatively affected FE (P PXR gene expression in the distal intestine; PXR expression was higher with SBM than with SFM. The effect of the inclusion level of plant ingredients was significant (P IL-Iβ gene expression in the spleen. Feed intake, FE, NRE, ERE, whole body crude protein, lipid, gross energy, and organo-somatic indices were significantly (P

Áreas inundadas de reservatórios e lagos artificiais estão sendo cada vez mais utilizadas para a produção de peixes; contudo, os resíduos lançados pela aquicultura tornaram-se uma preocupação para o desenvolvimento sustentável desta atividade. Uma das principais estratégias adotadas pelos órgãos gestores e fiscalizadores consiste no uso de modelos hidrodinâmicos que calculam a capacidade de suporte ou de carga de nutrientes de um determinado corpo hídrico e a influência dos cultivos de peixes. Esses modelos são precisos no desenvolvimento de estratégias ideais de alimentação e cálculo de resíduos. Este artigo de revisão aborda esta temática e traz uma descrição da metodologia desenvolvida para análise e simulação da capacidade de suporte para produção de pescados, baseada na integração do modelo bioenergético nutricional “Fish-PrFEQ” com o modelo hidrodinâmico de Dillon & Rigler. Esta metodologia permite avaliar a real contribuição de resíduos aquícolas e auxilia no planejamento e na gestão da aquicultura nestes ambientes aquáticos, além de possibilitar e incentivar que os produtores e a indústria aquícola utilizem rações de melhor qualidade nutricional e menor impacto ambiental. Flooded areas of reservoirs and artificial lakes have been increasingly used for fish production; however, the waste generated by aquaculture has become a concern for the sustainable development of this activity. One of the main strategies adopted by management and regulatory agencies is the use of hydrodynamic models that calculate the carrying or nutrient load capacity of a particular water body and the effect of fish farming. These models are precise in the development of optimal strategies for feeding and waste calculation. This review paper addresses this topic and describes the methodology developed for the analysis and simulation of the carrying capacity for fish production, based on the integration of the Fish-PrFEQ nutritional bioenergetic model and the hydrodynamic model of Dillon & Rigler. This methodology allows evaluating the real contribution of aquaculture waste and assists in the planning and management of aquaculture in these aquatic environments, besides enabling and encouraging producers and the aquaculture industry to use fish food with better nutritional quality and lower environmental impact.

The present study assessed the suitability of an FT-Raman method previously developed in our laboratory to predict the digestibility of crude protein (CP) in feather meals (FeMs) fed to rainbow trout (Oncorhynchus mykiss). Since we have already demonstrated that this FT-Raman method could efficiently predict the digestibility of CP in FeMs fed to broiler chickens, we decided to assess the suitability of this method in rainbow trout nutrition. A digestibility trial was conducted to assess the apparent digestibility coefficient (ADC) of CP in 7 FeMs of different origins in rainbow trout. Levels of disulphide conformers trans-gauche-trans (SStgt), gauche-gauche-trans (SSggt) and gauche-gauche-gauche (SSggg) in the 7 FeMs were studied by means of FT-Raman spectroscopy. Values of ADC were regressed against disulphide conformers to determine the presence of linear and quadratic correlations. The ADC of CP in the FeMs ranged from 0.64 to 0.71. Significant (P This study indicated that the ileal digestibility of CP in FeM may be affected by SStgt levels, which can be used as predictors of ADC of CP in FeMs fed to rainbow trout.

Simple Summary Aquaculture is the world’s fastest growing sector of the global food system. Aquaculture feed producers are seeking substitutes for fishmeal and fish oil to develop more sustainable feeds. Marine microalgae show promise as potential ingredients in aquafeeds; however, the literature lacks data on the digestibility and availability of macronutrients and individual fatty acids for omega 3-rich microalgal biomass, Schizochytrium spp., in rainbow trout. This is an important gap to fill because, among marine microalgae, this species is the most frequently used in fish feed, particularly as a dietary supplement or mixed with other ingredients; digestibility data would guide more judicious inclusion of this microalga biomass. High digestibility of macronutrients, energy and fatty acids showed that Schizochytrium spp. is a high-quality substitute for fish oil and potential candidate as a supplement of LC-PUFA in trout feed with vegetable oils. Digestibility is influenced by temperature and several trials have shown increased macronutrient digestibility with increasing temperature. There is an urgent need to determine the effect of temperature on lipid and fatty acid digestibility. We found that the digestibility of nutrients in rainbow trout maintained at 8 °C or 15 °C was not significantly different. However, the digestibility of DHA omega 3 was significantly higher at 8 °C than at 15 °C. Abstract Aquaculture feed formulation has recently turned its focus to reduce the reliance on marine-derived resources and utilise alternative feedstuffs, as an approach to improve the environmental sustainability of the aquaculture sector. The fish oil market is highly volatile, and availability of this commodity is continuously decreasing for use in aquaculture. Currently, a growing number of commercial efforts producing microalgae are providing omega 3-rich oil for sustainable aquaculture feed. This study was focused to determine the nutrient digestibility of a marine microalga, Schizochytrium spp., which is rich in docosahexaenoic acid (DHA) and long-chain polyunsaturated fatty acids (LC-PUFA), as a novel dietary lipid source that could be utilized effectively by rainbow trout (Oncorhynchus mykiss). A whole-cell Schizochytrium spp. biomass was used in the digestibility experiment at two different temperatures, 8 °C and 15 °C. No significant differences were detected between the two temperatures for the apparent digestibility coefficients (ADCs) of the dry matter (94.3 ± 4.9%), total lipids (85.8 ± 0.0%), crude proteins (89.5 ± 1.8%), energy (83.1 ± 1.7%) and fatty acids (85.8 ± 7.5%). The ADCs of the nutrients, energy, DHA and other fatty acids showed that Schizochytrium spp. is a high-quality candidate for fish oil substitution and supplement of LC-PUFA in fish feed with vegetable oils.

The present study assessed the suitability of a three-enzyme pH-stat method and of novel FT-Raman methods to predict the ileal digestibility of crude protein (CP) in feather meals (FeMs). A broiler digestibility trial was conducted to assess the ileal digestibility of crude protein in nine FeMs of different origins. One of the nine FeMs (FeM9) was the pre-treated ingredient stream of a commercially available FeM (FeM8). The pre-treatment was previously developed in our laboratory and consists of incubating FeM in 200% distilled water (%FeM w/w), with 0.5% of a commercial protease (%FeM w/w) and 2% sodium sulphite (%FeM w/w) at 55 °C for 24 hr in a shaking incubator. The degree of hydrolysis (DH) was measured after 10 minutes using a three-enzyme pH-stat method. Levels of disulphide conformers trans-gauche-trans (SStgt), gauche-gauche-trans (SSggt) and gauche-gauche-gauche (SSggg) in the nine FeMs were studied by means of FT-Raman. The effects of the disulphide conformers and of their interactions on AIDCP and SIDCP in FeM were assessed by analysis of variance (ANOVA) and fitted using a third-order interaction model. The coefficient of apparent ileal digestibility of CP (AIDCP) in the FeMs ranged from 0.368 to 0.594, whereas the coefficient of standard ileal digestibility of CP (SIDCP) ranged from 0.398 to 0.644. The pre-treatment significantly improved (P This study highlights that the ileal digestibility of CP in FeM is greatly affected by the disulphide bond conformers present, which can be used as predictors of AIDCP and SIDCP.

The aim of this study was to replace 75% of total fish oil (FO) and alter digestible protein/digestible energy (DP/DE) in rainbow trout feeds to minimize potentially hazardous environmental contaminant exposure. Two diets differing in DP/DE ratios (18 and 25) were combined with soybean (SO), canola (CO), and a blend of canola oil and Schizochytrium sp. (COS). Dietary lipids and DP/DE ratios did not affect apparent digestibility, growth, and somatic parameters. The n-3/n-6 levels decreased significantly in the growth trial, especially for the SO groups. A short washout trial restored n-3/n-6 levels for the CO and COS groups, irrespective of the DP/DE ratio, but not for the SO groups. At all sampling events, contaminant concentrations in fish flesh were lower than limits set by regulatory agencies in Canada, the US, and Europe. Contaminants were lower in the oil replacement diets compared to FO for toxaphenes, organochlorine pesticides, and PCBs but not flame retardants during the growth phase. At the end of the washout phase, no differences were detected. Thus, this study revealed that replacing 75% of total fish oil in rainbow trout feed by CO and COS, combined with a 25 DP/DE ratio, with a washout period seems to be the most efficient approach in terms of maximizing the total FO replacement and contribute to reducing POPs exposure.

A growth trial was conducted to determine relative bioavailability between two commercially available sources of supplemental lysine in rainbow trout. A basal diet, which was formulated to be deficient in lysine while meeting all other known nutritional requirements for rainbow trout was supplemented with increasing levels (0.1, 0.2, 0.4 & 0.6%) of l -lysine on an equimolar basis from one of two supplemental lysine sources; l -lysine sulfate (Bio-lys) or l -lysine HCl. Diets were fed in triplicate to groups of rainbow trout (IBW = 25 ± 0.6 g) for 12 weeks using a pair-feeding protocol. Fish which received diets containing supplemental lysine from either source exhibited improved weight gain (p 0.05) in bioavailability were observed between these two sources. Therefore, based on equimolar levels of l -lysine supplementation these two sources of supplemental lysine are equally available to rainbow trout. Statement of relevance The authors of this manuscript believe that there is a gap in the literature concerning the relative bioavailability between two prevalent sources of lysine to commercially relevant aquaculture species. Common plant protein ingredients, in particular cereal grain by-products, contain low levels of lysine. In order to formulate economical feeds, feed formulators supplement these primarily plant protein diets with supplemental sources of lysine in order to create economical diets while meeting all nutritional requirements of the animal. As the sources of lysine tested in this study, l -lysine HCl and l -lysine sulfate, are both used in the formulation of aqua feeds the relative ability of these two sources to meet the lysine requirement of rainbow trout (a major species cultured in Canada) will allow for feed formulators to use economic feed ingredients, while being confident the source of supplemental lysine they are using (either l -lysine HCl or l -lysine sulfate) will be used equally well to meet the fishes' lysine requirement.

Different synthetic forms of supplemental methionine (Met) are produced commercially by various manufacturers. Limited information exists on the bioavailability of these different forms in commercially relevant fish species. The objective of this study was to compare the relative bioavailability of L-methionine and a methionine hydroxy analogue calcium salt (MHA-Ca) to DL-methionine in a commercially relevant species, rainbow trout, using a linear slope-ratio assay. In addition, the ability of the rainbow trout to effectively convert the D-isomer of methionine into the biologically active L-isomer was studied by comparing the relative bioavailability of L-methionine to DL-methionine. Nine (9) diets were created from a methionine-deficient basal diet which was supplemented with graded equimolar levels of methionine (0.1%, 0.2%, 0.3% of diet by weight) from either DL-methionine, L-methionine and methionine hydroxy analogue calcium salt (MHA-Ca). Diets were fed in triplicate (IBW = 24.0 � 0.6 g) for 12 weeks using a pair-feeding protocol. The basal diet was formulated to be deficient in both methionine (0.5%) and cysteine (0.3%), whereas meeting all other known nutritional requirements of rainbow trout. MHA-Ca was found to be less available (P 0.05) in bioavailability were found between DL-methionine and L-methionine. These findings lead to the conclusion that differences in bioavailability do exist between sources of synthetic methionine, additionally findings suggest that rainbow trout are able to effectively convert the D-isomer of methionine into the L-isomer without significantly affecting fish performance.

An 8-week feeding trial was conducted to examine effects of wheat naturally contaminated with Fusarium mycotoxins (deoxynivalenol, DON 41 mg·kg−1) on growth performance and selected health indices of red tilapia (Oreochromis niloticus × O. mossambicus, initial weight = 4.3 g/fish). Five experimental diets were formulated by replacement of clean wheat with naturally contaminated wheat resulting in graded levels of DON and zearalenone (ZEN) (Diet 1 0.07/0.01, Diet 2 0.31/0.09, Diet 3 0.50/0.21, Diet 4 0.92/0.37 and Diet 5 1.15/0.98 mg·kg−1). Groups of 50 fish were randomly allocated into each of 20 aquaria and fed to near-satiety for eight weeks. Growth rate, feed intake and feed efficiency of fish fed the experimental diets decreased linearly with increasing levels of Fusarium mycotoxins (p &lt, 0.05). Although growth depression was associated with feeding diets naturally contaminated with Fusarium mycotoxins, especially DON, no biochemical and histopathological parameters measured in blood and liver appeared affected by Fusarium mycotoxin concentrations of diets (p &gt, 0.05). Though there was no clear evidence of overt DON toxicity to red tilapia, it is recommended that feed ingredients should be screened for Fusarium mycotoxin contamination to ensure optimal growth performance.

Saez, P. J., Abdel-Aal, E. M. and Bureau, D. P. 2015. Reduction of carotenoids in corn gluten meal: Effects on growth performance and muscle pigmentation of rainbow trout (Oncorhynchus mykiss). Can. J. Anim. Sci. 95: 79–92. Corn gluten meal (CGM) is an ingredient widely included in aquaculture feeds. The use of significant levels of CGM in diet formulation has been anecdotally related to the suboptimal pigmentation of the muscle of salmonid fish. The results of a few scientific studies that have examined the effect of CGM on muscle pigmentation in salmonids remain inconclusive. Therefore, a bench-scale study was carried out to reduce the content of yellow xanthophyll carotenoids in CGM using white soy flake flour as a bleaching agent. A 12-wk growth trial was then conducted to assess the effects of treated CGM on growth and muscle pigmentation of rainbow trout (Oncorhynchus mykiss) in comparison with regular CGM. Results of the pigment reduction study indicated that the concentration of lutein, zeaxanthin, β-cryptoxanthin and β-carotene was reduced by 86, 97, 100 and 100%, respectively, in the treated CGM. Results of the growth trial showed that the inclusion of treated or regular CGM in the diet did not significantly affect growth performance. However a significant (P−1 of regular CGM when compared with the fish fed the control diet (0 g kg−1 of CGM). The muscle of fish fed the diet containing 190 g kg −1 of treated CGM showed the lowest astaxanthin deposition. This could be attributed to the presence of reactive peroxy radicals produced during the reduction of carotenoids in the treated CGM. Further research is underway to improve the processing method for the reduction of carotenoids in CGM.

Although dietary lipid quality markedly affects fatty acid (FA) composition of mitochondrial membranes from rainbow trout red muscle (Oncorhynchus mykiss), mitochondrial processes are relatively unchanged. As certain classes of phospholipids interact more intimately with membrane proteins than others, we examined whether specific phospholipid classes from these muscle mitochondria were more affected by dietary FA composition than others. To test this hypothesis, we fed trout with two diets differing only in their FA composition: Diet 1 had higher levels of 18:1n-9and18:2n-6thanDiet2,while22:6n-3and22:5n-6werevirtuallyabsentfromDiet1and high in Diet 2. After 5 months, trout fed Diet 2 had higher proportions of phosphatidylcholine (PC) andlessphosphatidylethanolamine(PE) inmitochondrialmembranesthanthosefedDiet 1.TheFA composition of PC, PE and cardiolipin (CL) showed clear evidence of regulated incorporation of dietary FA. For trout fed Diet 2, 22:6n-3 was the most abundant FA in PC, PE and CL. The n- 6F A were consistently higher in all phospholipid classes of trout fed Diet 1, with shorter n-6 FA being favoured in CL than in PC and PE. Despite these marked changes in individual FA levels with diet, general characteristics such as total polyunsaturated FA, total monounsaturated FA and total saturatedFAwereconservedinPEandCL,confirmingdifferentialregulationoftheFAcomposition of PC, PE and CL. The regulated changes of phospholipid classes presumably maintain critical membranecharacteristicsdespitevaryingnutritionalquality.Wepostulatethatthesechangesaim to protect mitochondrial function.J. Exp. Zool. 9999A: XX-XX, 2014. © 2014 Wiley Periodicals, Inc. How to cite this article: Martin N, Kraffe E, Le Grand F, Marty Y, Bureau DP, Guderley H, 2014. Dietary fatty acid composition and the homeostatic regulation of mitochondrial phospholipid classes in red muscle of rainbow trout (Oncorhynchus mykiss). J. Exp. Zool. 9999:1-12.

This study investigated the effect of dietary astaxanthin supplementation on egg quality and juvenile growth of long snout seahorse (Hippocampus guttulatus). Captive breed seahorse broodstock were fed four diets composed of frozen shrimp [Atlantic ditch shrimp, Palaemonetes varians) used as a vector to deliver artificial diets with increasing levels of astaxanthin (0, 75, 100 and 125 mg kg(-1) dry weight)]. The results indicated that the astaxanthin uptake into eggs from the enriched shrimp diets was highly efficient. Females fed unsupplemented astaxanthin diet produced similar-sized eggs with lower concentration of astaxanthin than females fed diets with astaxanthin. The lower concentration of astaxanthin in the eggs was correlated with the production of smaller juveniles in comparison with the juveniles hatched from parents fed supplemented astaxanthin diets. Juvenile growth and survival was limited by their size on release from the male's pouch as at the end of 28-day postparturition juveniles produced with the diet with no astaxanthin were still significantly smaller (P < 0.05) than those produced from parents fed astaxanthin-supplemented diets. These results demonstrate a significant benefit of dietary astaxanthin supplementation in long snout seahorse diets in terms of improved egg quality and juvenile growth and survival. FCT - Portugal [BPD/34816/2007] info:eu-repo/semantics/publishedVersion

9 páginas, 6 tablas, 4 figuras., Two models were derived in an effort to better describe the indeterminate nature of growth exhibited by ectotherms. The models are characterized by their non-sigmoidal shape and are based on three assumptions: quantity of growth machinery works at a rate dependent on feed intake; the relationship between growth rate and intake level follows the law of diminishing returns; and growth is irreversible. The Michaelis–Menten and Mitscherlich equations are used in their formulation. To investigate their potential, the models were fitted to six datasets, representing repeated measures of live body weights of two species: rainbow trout (Oncorhynchus mykiss) and Nile tilapia (Oreochromis niloticus). The models were evaluated on the basis of fitting behaviour, examination of residuals, along with measures of goodness-of-fit. Agreement between predicted and observed body weights, and flexibility to mimic growth patterns given varying species and culture conditions, affirm the ability of both models to describe indeterminate growth in fish., This work was supported by The Canada Research Chairs program, Grant #045867 (Natural Sciences and Engineering Research Council, Ottawa).

A 24-week growth trial was conducted to evaluate the effects of feeding levels of corn gluten meal (CGM) on growth performance and pigment deposition in the muscle of rainbow trout (Oncorhynchus mykiss). Three isonitrogenous and isoenergetic (digestible energy basis) experimental diets were formulated to contain increasing levels of CGM (0%, 9% and 18%) and 50 mg kg � 1 of astaxanthin. Each diet was fed in triplicate to groups of 75 fish (initial average body weight = 549 g fish � 1 ) reared at 8.5°C. The inclusion of CGM did not significantly (P > 0.05) affect final body weight, thermal growth efficiency (TGC) or feed efficiency. Carotenoid concentration determined by liquid chromatography showed a significant (P < 0.05) linear reduction in the concentration of one astaxanthin isomer, all-trans astaxanthin and all-trans lutein in the muscle of fish in response to increasing levels of CGM. Tristimulus colour analysis of the muscle showed a significant (P < 0.05) linear reduction in a* (redness) and C*ab (chroma). Salmofan TM score showed a significant (P < 0.05) linear and quadratic reduction in response to increasing levels of CGM. In conclusion, the inclusion of CGM up to 18% does not significantly impact growth performance of rainbow trout. However, the concentration of all-trans astaxanthin as well as the expression of important colour attributes of the muscle can be negatively affected at levels exceeding 9% of CGM in the diet. More research on this topic is needed to discern the mechanism(s) behind the negative effects of dietary CGM and/or its intrinsic yellow pigments on muscle pigmentation of rainbow trout.

The effect of dietary phytic acid (PA) and semi-purified lignin, and their interactions on growth performance, energy storage indices, nutrient deposition and partitioning in rainbow trout were studied in a 12-week growth trial. Six isoproteic and isoenergetic diets were formulated differing only in their PA and lignin concentrations. In these diets, five essential amino acids: histidine, lysine, methionine (+ cysteine), threonine and tryptophan were formulated to be marginally adequate to the dietary requirement. Fish were pair-fed with the amount of feed adjusted on a weekly basis. Among the performance indicators, dietary PA levels affected only the Fulton's body condition index (FCI) and whole carcass nitrogen retention efficiency (NRE; P

The objective of this study was to determine if deoxynivalenol (DON) exposure alters the susceptibility of rainbow trout to bacterial coldwater disease caused by Flavobacterium psychrophilum. Rainbow trout were fed a nutritionally complete diet containing corn that was naturally contaminated with DON at a desired concentration of

Extended phosphorus (P) deficiency has been linked to an increase of skeletal deformities in farmed salmonids. To date, X-ray examination still is the most practical way to detect abnormalities that are not externally visible. The aim of this study was to develop a standardized method based on empirical measurements that provides an early radiograph-based detection of deformities. Triploid all-female rainbow trout (60.8 +/- 1.6 g) were fed with phosphorus (P)-deficient and P-sufficient diets (total P = 0.5% and 0.92%, respectively). Experiments were carried out in 12 circular re-circulating tanks (n = 140/tank; 8.5-52.7 kg m(-3); 12 +/- 0.3 degrees C; 18L: 6D). All fish were x-rayed at week 5, 15 and 24 to monitor vertebral abnormalities. Fish were assigned to a vertebral phenotype (normal, biconcave or compressed) when all vertebrae of the caudal region (V31-44) showed the same type of abnormalities. At week 9, 18 and 27, ten fish per tank were randomly sampled according to their vertebral phenotype. Vertebrae V38-V39 were collected and a second X-ray was performed to confirm the above-mentioned phenotypes. Morphometrics (vertebral length and height; intervertebral distances and vertebral body angles) were measured directly on radiographs. For all parameters measured, comparisons were made between normal P-sufficient fish and different scenarios of vertebral development (normal, restored, stable and aggravated) in P-deficient fish. The two parameters showing the most sensitivity were the median intervertebral distance and dorsal/ventral vertebral endplate angles. When analysed together, these two parameters allow a quantitative distinction of the different vertebral phenotypes. Measuring dorsal/ventral vertebral endplate angles seems a promising approach to detect aberrant vertebral development at early stages as slight changes were observed in P-deficient vertebrae that were assessed as normal by visual examination. Further studies including histological examinations and comparison with other radiological imaging techniques are required to confirm these results.

Relative bioavailability (RBV) of arginine (Arg) from Indian mustard protein concentrate (IMC, 62% crude protein) and Indian mustard meal (IMM, 42% crude protein), and a commercially available soy protein concentrate (SPC, 57% crude protein) was compared with that of crystalline L-arginine (L-Arg) in rainbow trout. A basal diet highly deficient in Arg (1.23%) was formulated. Eight other isoproteic and isoenergetic diets were formulated to contain ~1.35% and ~1.5% Arg by adding increasing amount of IMC, IMM, SPC and L-Arg. The experimental diets were fed for 16 weeks using a standard protocol. Growth rate, weight gain (g fish � 1 ) and protein (PD, g fish � 1 ) and lipid (LD, g fish � 1 ) deposition were increased linearly with increasing level of Arg from all ingredients. Arg availability from protein-bound sources were equal or higher than those from L-Arg. RBV of Arg from IMC, IMM and SPC were ranged from 100% and 123% than that from L-Arg (assumed as 100% bio-available). Among the ingredients, only the RBV of Arg from IMC was significantly higher than those from SPC (P < 0.05). The findings suggest that the RBV of Arg from IMC and IMM are very good and comparable to that of the commercial SPC used in this study.

As fish feeds are increasingly being formulated with a variety of economical protein sources, more attention needs to be paid to ensure that the essential amino acids (EAAs) requirements of the fish are met adequately. A novel factorial AA requirement model was developed by incorporating the effect of dietary and biological factors on AA requirement and utilization for two salmonid fish species, Atlantic salmon and rainbow trout. The factorial model determines AA requirement of fish based on species, expected body weight gain, body protein deposition, AA profile in body protein deposition, maintenance AA requirement, and inevitable AA metabolism. Simulation using this novel model suggests that EAA requirement (expressed as % diet DM) progressively decreases when the live weight of the fish increases. Atlantic salmon appears to have higher EAA requirements (estimated as % diet DM) than rainbow trout at the same body weight classes, and the rate of decrease in EAA requirement with the increase of body weight appears to be slower in Atlantic salmon. Model simulations also suggest that the composition of the diet composition also influences the estimates of EAA requirements. The novel factorial model could be a helpful tool in formulating cost-effective aquaculture feeds. This modelling approach can be adapted to other fish species.

This study was carried out to estimate lysine, methionine and arginine dietary requirements of juvenile Atlantic ditch shrimp, Palaemonetes varians. Three series of five isoproteic and isoenergetic diets [45% crude protein (CP), 14.7 MJ digestible energy (DE)/kg] were formulated to contain increasing levels of either lysine (1.2–2.8 g/100 g of diet), methionine (0.5–1.3 g/100 g of diet + 0.8% cysteine) or arginine (1.1–2.7 g/100 g of diet) and adequate levels of all other essential nutrients. Each experimental diet was fed to three groups of postlarvae (initial weight = 17 mg each) for 45 days at 19.9 ± 0.1°C. The dietary requirements for maximizing weight gain of juvenile P. varians, estimated using broken-line analysis vs. exponential model and expressed as per cent of dry diet, were 2.42 vs. 2.63; 0.96 vs. 0.99 and 2.05 vs. 2.39 for lysine, methionine and arginine respectively. These estimates of requirements of lysine, methionine and arginine for juvenile P. varians appear to be similar to those reported for penaeid shrimp species.

A feed requirement and waste output model for commercial tilapia production was developed using the Fish-PrFEQ bioenergetics factorial approach and by an integration of data from commercial sources and the scientific literature. Different growth models were compared to determine the growth trajectory during three different production stages (nursery, 1–30 g body weight (BW); pre-growout, 30–220 g BW; and growout, > 220 g BW) based on data from a commercial tilapia farm in Ecuador. Feed requirement was estimated based on digestible energy requirement (DE req ), calculated from the expected energy gain (recovered energy, RE), and estimates of energy losses associated with basal metabolism (HeE), heat increment of feeding (HiE), and urinary and branchial excretion (UE + ZE), all estimated by compiling and analysing data from published studies. The waste outputs were estimated using a nutrient mass balance approach. Feed requirement model simulations were compared with the results from a growth trial carried out under controlled conditions. The modified TGC models produced a better fit of the growth trajectory of the fish on the commercial farm across production stages compared with other growth models (specific growth rate, linear model). Values predicted for body weight ( r = 0.998, P r = 0.849, P

The issue of sustainability of salmonid culture has been the focus of considerable media coverage and debate between environmental activists and aquaculture industry stakeholders, particularly regarding the use of ingredients derived from wild fisheries (fishmeal and fish oil) in salmonid feeds. This study attempts to summarize recent data and to calculate the conversion efficiency of feed resources by Canadian farmed salmon in order objectively to assess the sustainability of this industry in this regard. Using updated information regarding domestic aquafeeds this review reports advances that have been made in diet formulation, fish in-fish out (FIFO) and feed conversion ratios (FCR) and demonstrates that production efficiency of farmed salmonids has significantly improved over time due to continued innovations in the aquafeed sector. The results suggest that the Canadian salmon aquaculture industry efficiently converts wild fish resources into high-value fish products.

This investigation examined the effect of using enriched shrimp (Atlantic ditch shrimp, Palaemonetes varians) diets on growth of long snout seahorse, Hippocampus guttulatus, and its effect on the reproduction rate and brood quality. Three diets were (1) natural wild-caught shrimp (natural shrimp diet-control diet), (2) wild-caught shrimp fed an artificial feed for 10 d (enriched shrimp diet), and (3) wild-caught shrimp fed one large meal of artificial diet and immediately frozen (ingested artificial feed shrimp diet). These diets were fed to seahorses during a 12-wk growth trial. At the end, significant differences on the final wet weight were found between seahorses fed the three different treatments (P < 0.009). Seahorses fed ingested artificial feed shrimp diet had more broods (9), generated more juveniles per brood (299 ± 87), and significantly bigger juveniles (12.4 ± 1 mm) than seahorses fed natural shrimp diet and enriched shrimp diet. Significant differences in the morphometry of juveniles hatched from parents fed the three different dietary treatments (Wilk's λ = 0.2, F(6,460) = 47.41, P < 0.0001) were also found. Results indicate that the combined use of a natural diet (shrimp) and an artificial diet benefit growth and feed utilization by seahorses and have a direct impact on the reproductive rate and brood quality of H. guttulatus.

Digestibility trials were carried out to determine the apparent digestibility of amino acids (AA) of two novel plant protein ingredients, Indian mustard protein concentrate—(IMC, 62% crude protein) and Indian mustard meal (IMM, 42% crude protein) produced through a low temperature process, and a commercially available soy protein concentrate (SPC, 57% crude protein) in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). The apparent digestibility coefficient (ADC) of crude protein (CP) from IMC was 90% and 97% for trout and salmon, respectively. The ADCs of CP from IMM and SPC were also very high (> 95%) for both species. The ADCs of lysine (95%), isoleucine (91%), leucine (86%) and phenylalanine (90%) from IMC were slightly lower (P 90%). These results suggest that low glucosinolate Indian mustard protein concentrate and Indian mustard meal are ingredients of high nutritive value. However, it is hypothesized that the high phytic acid level in the Indian mustard protein concentrate may negatively affect the digestibility of CP and certain amino acids when used at high level in the feed of fast growing fish.

Numerous studies have been carried out to test the effect of incorporating various protein sources in salmonid fish feeds at the expense of fish meal. Comparison and interpretation of the results from these studies are difficult given the wide differences in ingredients, feed formulations, experimental designs and achieved performance. The objective of this study was to contrast two approaches for analyzing and comparing the results of such studies: meta-analysis and nutritional model simulation. The meta-analysis indicated that compared to fish meal-based diets, low or moderate dietary incorporation of plant protein ingredients in general did not affect growth of salmonids, whereas fish growth was depressed at high dietary inclusion levels of plant protein ingredients even when the diets were apparently nutritionally adequate. Feed intake was not negatively affected as long as the diets were nutritionally adequate. Sources of plant protein ingredients also appear to have divergent effects on fish growth. The scope of the meta-analysis was limited due to measures to ensure the meaningfulness of the meta-analysis. Therefore a novel integrated growth and nutrient utilization model was developed and used as a simulation tool to achieve a broader and more rational comparison of studies. Overall the model adequately predicted growth of salmonids fed diets containing different levels of plant protein ingredients. The model simulation-based approach allowed a proper quantification of the effect of plant protein sources in salmonid fish feeds.

The aim of this study was to determine suitable Artemia enrichment and feeding protocols for the rearing of juvenile long snout seahorse, Hippocampus guttulatus from birth. The first phase of the project, examined the effect of two different Artemia enrichments treatments (DHA-Selco®, and Chlorella sp.) on the growth performance and survival of early-stage juvenile H. guttulatus . DHA-Selco® enrichment of Artemia resulted in a null survival at 10 days post parturition (DPP) whereas the use of Artemia enriched with Chlorella sp. resulted in 20% survival at the end of 60 DPP. The second phase of the study (60 to 120 DPP) reported the progressive feed transition of juvenile seahorse from Artemia to live shrimp ( Palaemonetes varians ) and from live to frozen shrimp and its effect on growth performance and survival of the juveniles. Overall, the mean standard length of juvenile H . guttulatus increased from 1.4 ± 0.05 cm at release from male's pouch to 12.4 ± 1.2 cm at 120 DPP. Mean juvenile wet weight increased from 4.2 ± 0.2 mg to 4133 ± 1230 mg in that same period. Length, wet weight, daily weight gain and thermal-unit growth coefficient were used to characterise juvenile H . guttulatus growth performance, which was found to be similar to that of published accounts for other juvenile seahorse species at the same life stage. This study is the first record of successful rearing of H . guttulatus juveniles in captivity, and offers a promising starting point to improve the rearing techniques to successfully breed this candidate aquaculture species.

A 12-week slope ratio growth assay was undertaken to estimate the bioavailability of arginine in feather meal fed to rainbow trout. Fish were fed to satiety with isonitrogenous and isoenergetic diets containing graded levels of arginine provided by either synthetic l -arginine or steam-hydrolysed feather meal. Weight gain of the fish responded in a significantly linear (P l -arginine. Weight gain of the fish did not significantly improve with increasing arginine level provided by feather meal. This result was unexpected since all diets were formulated to contain digestible essential amino acid (EAA) levels that were significantly in excess of NRC (1993) requirements. However, significant improvement in the feed efficiency, as well as nitrogen and energy utilization efficiencies, of fish fed the diets with increasing levels of feather meal, suggests that digestible nutrients from feather meal were, on average, very efficiently utilized by the fish. In a follow up experiment, supplementation of a high feather meal diet from the first experiment with a mixture of synthetic EAA significantly (P This study highlights the need to have more accurate information on EAA requirements of fish for the development of slope ratio assays aimed at assessing the bioavailability of amino acids in different ingredients. It also shows the importance of generating more information on the bioavailability of individual EAA in feather meals.

Nutrients released by cage fish farms to the aquatic environment are an issue of concern since these can result in deleterious environmental changes. In the present study, a mass balance model was used to calculate nutrient loadings from an experimental rainbow trout cage farm located in a freshwater, oligotrophic lake. Detection of these nutrient loadings using water quality monitoring was then investigated. The loading of total solids of faecal and feed origin (TS), solid phosphorus (SP) and nitrogen (SN), and dissolved P (DP) and N (DN) wastes from the farmed fish were estimated over two production cycles. Waste outputs were estimated using the Fish-PrFEQ feed requirement and waste output model using measured inputs including diet composition, nutrient digestibility, intake and retention by the fish, and water temperature. Nutrient loading predictions were compared with measured nutrient concentrations of lake water. In 2003, TS, SN and SP and DN and DP waste outputs were 236.0, 12.8, 5.3, 41.3, and 3.4 kg tonne − 1 of fish produced, respectively. In 2004, the TS, SN and SP and DN and DP waste outputs were 220.0, 12.2, 5.3, 38.0, and 3.4 kg tonne − 1 of fish produced, respectively. Over 60% of the P waste output from the cage was predicted to be solid for both years while over 65% of the total N waste from the cage farm was predicted to be excreted as ammonia. Concentrations of ammonia and of dissolved and particulate phosphorus were not reflective of waste loading of cage origin, suggesting efficient removal through uptake by biota and/or in the case of ammonia by nitrification. Fish-PrFEQ model is a valuable cage management tool that allows realistic estimation of waste outputs for cage farms and can be used to examine effect of management and feeding practices on waste outputs. However, the model is of limited use as a lake management tool, as it does not consider effects and fate of wastes released by fish. Similarly, reliance on periodic water quality monitoring at stations near cage farms may not be protective of the environment, as our results demonstrate that rapid diffusion, uptake, transformation and removal of nutrients resulted in water quality measures that were relatively insensitive to cage loading. Combining the Fish-PrFEQ model with a consideration of assimilative capacity of the system in addition to the monitoring of chemical and biological variables of the lake is recommended for environmental impact assessment of cage culture operations.

Deoxynivalenol (DON), a Fusarium mycotoxin, is a major contaminant of cereal grains worldwide. The effects of feeding six diets containing low, graded levels of DON from two naturally contaminated sources of corn on the performance, health and apparent nutrient digestibility of rainbow trout were investigated. Feeding diets with increasing levels of DON (0.3, 0.8, 1.4, 2.0 and 2.6 ppm) for eight weeks to rainbow trout (initial weight = 24 g/fish) resulted in significant linear or quadratic decreases in feed intake, weight gain, growth rate (expressed as thermal-unit growth coefficient, TGC), feed efficiency (FE, gain:feed), retained nitrogen (RN), recovered energy (RE), energy retention efficiency (ERE), and nitrogen retention efficiency (NRE). Fish pair-fed the control diet (0.3 ppm DON) had significantly higher TGC (P 0.05) were observed in the apparent digestibility coefficients (ADC) of CP and gross energy (GE) of fish fed diets containing 0.3 (control) to 2.0 ppm DON. In addition, some morphological changes of the liver were noted in fish fed the diet containing 2.6 ppm DON. These results suggest that, relative to other species, rainbow trout are extremely sensitive to DON from naturally contaminated grains and that the effects of DON on rainbow trout are not simply related to a reduction of feed intake, but rather, are due to metabolic effects. More research is required to identify the specific mechanism(s) of toxicity of DON in rainbow trout.

Accurate estimates of phosphorus (P) digestibility are essential to enable the formulation of cost-effective diets meeting P requirement of fish but resulting in minimal P waste outputs. Evidence suggests that differences in P digestibility exist among fish species but they have not been quantified. A modelling approach was employed in this study to quantify these differences. As a first step, an existing mathematical model of P digestibility developed for salmonids was statistically evaluated to determine if this model could be extrapolated to predict digestible P content in feeds of two widely cultured groups of freshwater fish species, tilapias (cichlids species) and carps (cyprinid fish species) or if modification was required. Subsequently, two novel mathematical models specific for tilapias and carps were developed. Results suggest that significant differences in P apparent digestibility exist among cyprinids, cichlids, and salmonids. Cyprinid species appear to have low ability to digest P compounds of low solubility. They do not appear to be able to effectively digest bone P (digestibility of bone P was estimated to be nil), and their ability to digest dibasic calcium phosphates is low (30%) in comparison to that of cichlids and salmonids (which is in the ranges of 62-64%). These differences could be attributable to the absence of an acid stomach in cyprinids. Cyprinids and salmonids appear to be unable to digest phytate-P from plant ingredients, while tilapias seem to be able to digest phytate-P to a certain degree (approximately 27%). These mathematical models could be useful tools to estimate the digestible phosphorus content of feeds formulated with a wide variety of ingredients fed to fish species with different digestive anatomy and physiology.

Long-term sustainability of many fish culture operations may be dependent on their ability to reduce their waste outputs. The release of solid wastes is mainly a function of the digestibility of various dietary components, and the release of dissolved wastes is mainly a function of the metabolism of nutrients by the fish. Consequently, simple principles of nutrition and models have been effectively used to describe, predict and manage the excretion of wastes by fish. Nutritional strategies offer a direct and effective way of managing waste output by aquaculture operations. Very significant reduction in waste outputs per unit of fish produced, notably in terms for solid and phosphorus wastes, have been achieved over the past few decades by commercial fish culture operations. Further reduction in waste outputs could be achieved through fine-tuning of feed formulations, judicious use of feed additives and processing/refining of ingredients. A better understanding of the basis of the effect of various endogenous (biological) and exogenous (dietary, environmental) factors on nutrient utilization by fish could also contribute to the development of strategies for reducing waste outputs. The present paper provides a brief overview of issues and challenges related to potential environmental impacts of wastes, and of recent progresses relative to nutritional strategies aimed at better management of the release of wastes by aquaculture operations.

Aquaculture's pressure on forage fisheries remains hotly contested. This article reviews trends in fishmeal and fish oil use in industrial aquafeeds, showing reduced inclusion rates but greater total use associated with increased aquaculture production and demand for fish high in long-chain omega-3 oils. The ratio of wild fisheries inputs to farmed fish output has fallen to 0.63 for the aquaculture sector as a whole but remains as high as 5.0 for Atlantic salmon. Various plant- and animal-based alternatives are now used or available for industrial aquafeeds, depending on relative prices and consumer acceptance, and the outlook for single-cell organisms to replace fish oil is promising. With appropriate economic and regulatory incentives, the transition toward alternative feedstuffs could accelerate, paving the way for a consensus that aquaculture is aiding the ocean, not depleting it.

Digestibility of starch in salmonids is reported to be highly variable and affected by a number of factors, such as source or type, dietary inclusion level, and technological treatments of the starch or feed. A model was constructed to explain variation in digestibility of starch across studies and to estimate digestible starch content of salmonid fish feed by integrating data from 26 studies. The relationship between digestible starch content and physico-chemical state (raw and gelatinized starch) was modelled through a multiple regression approach. Multiple regression analysis yielded the following model: Digestible starch content (% of diet) = 0.560 raw starch − 0.011 raw starch 2 + 0.904 gelatinized starch − 0.009 gelatinized starch 2 + 0.016 temperature * raw starch + 0.009 temperature * gelatinized starch − 0.270 fish species * raw starch − 0.068 * fish species * gelatinized starch − 0.158 * faeces collection method * gelatinized starch ( P R 2 = 0.84; fish species = 0 for rainbow trout, 1 for Atlantic salmon; faeces collection method = 0 for passive collection, 1 for active collection). The model suggests that the digestibility of raw and gelatinized starches significantly differs and their digestibility is negatively affected by dietary inclusion levels. The model also revealed a significant effect of water temperature on starch digestibility and interspecies differences in the ability to digest starch. Faeces collection method was found to significantly contribute to the variability of starch digestibility reported across studies. The model was validated by an independent group of data, and can potentially be a useful tool for feed formulation.

This investigation examined the eiects of temperature, density and early weaning on the survival and growth of Palaemonetes varians larvae. Survival of larvae raised at 17.51C was not signi¢cantly diierent (average 1 standard deviation) (94 5%) from the survival of those raised at 19.51 C( 95 5%) and at 21.5 1 C( 94 4%). However, the duration of the larval stage was signi¢cantly longer for shrimp reared at 17.51 C( 17.3 0.8 days) compared with shrimp reared at 19.51 C( 14.3 0.7 days) and at 21.5 1 C( 11.3 0.6 days). No signi¢cant diierences (P40.05) were found in the survival rate, ¢nal weight and length of larvae reared at the densities of 5, 10, 20 and 50 larvae L 1 . The survival of P. varians larvae fed solely on Artemia was signi¢cantly higher (Po0.05) than larvae weaned with an arti¢cial practical diet from Zoea II stage (94 4% and 82 1%, respectively, for Artemia and arti¢cial diet-fed larvae), but no signi¢cant diierences (P40.05) were observed in the ¢nal larval weight or length between these two treatments. The survival and growth of the larvae fed with the practical diet tested is a promising step ahead in the development of the culture of this species as it eliminates both the need for Artemia throughout all larval stages, and the need for more expensive arti¢cial diets.

SUMMARYModels that accurately describe and predict growth and nutrient utilization of fish can be useful in developing strategies to improve the economic and environmental sustainability of aquaculture operations. Current bioenergetics models are not sufficiently flexible to be applied to the wide range of conditions encountered in aquaculture. There is a need to move from bioenergetics approaches to more mechanistic approaches based on nutrient utilization by fish. A non-ruminant nutrient-based growth model has been successfully used in pig production. The model explicitly describes the utilization of energy-yielding nutrients and metabolites for body protein deposition (Pd) and body lipid deposition (Ld) at the whole animal level. Partitioning of intake of energy-yielding nutrients between Pd and Ld is governed by a minimum ratio (minLP) of the body lipid mass (L) to protein mass (P), a maximum daily rate of Pd (PdMax), or maximum efficiency of using intake of the first limiting dietary essential amino acid (AA) for body Pd. The growth model was adapted to rainbow trout (Oncorhynchus mykiss (Walbaum 1792)) through parameterization and various modifications consistent with its framework. The fish nutrient-based model was evaluated by comparing model simulations with data from various experiments carried out with rainbow trout. Significant discrepancies between model predictions and experimental observations were observed. The model predicted energy retention well but did not always accurately predict growth rate, nor Pd and Ld. Overall, the model underestimated growth rate (expressed as thermal-unit growth coefficient (TGC)) by 37% and Pd by 15% and overestimated Ld by 13%. These discrepancies are probably attributable to differences in nutrient utilization and partitioning mechanisms between fish and pigs. The development of more reliable models requires better understanding of the nutritional and endogenous determinants of fish growth.

Two growth trials were conducted using spray-dried blood meal (BM), feather meal (FEM), meat and bone meal (MBM) and poultry by-product meal (PBM) as major protein sources in the diet of rainbow trout. In the first trial, five diets were formulated to examine the nutritive value of spray-dried BM and PBM. Increasing levels of BM (6, 12%) or PBM (10, 20, and 30%) replaced fish meal and corn gluten meal in the diet. For the second trial, eight diets were formulated to contain the following combinations: FEM + MBM, FEM + PBM or MBM + PBM. The diets containing FEM + MBM and FEM + PBM were supplemented with either L-lysine or DL-methionine, the amino acids predicted to be the two most limiting in these diets. Each experimental diet was allocated to three tanks of fish and fed for 20 weeks in the first trial or 16 weeks in the second trial. All the experimental diets were readily consumed by the fish and high growth and good feed efficiency ratio (FER) were achieved for all diets. In the first trial, there were no significant differences ( P > 0.05) in weight gain or FER of fish fed the five experimental diets, suggesting that BM and PBM had high nutritive values for rainbow trout. In the second trial, growth of the fish fed the diet containing the FEM + PBM combination was not statistically different from growth of fish fed the control diet. Growth of fish fed diets with FEM + MBM or PBM + MBM combinations were slightly lower than that of fish fed the control diet. Supplementation of diets with either L-lysine or DL-methionine had no effect on the performance of the fish. The results from this study show that feather meal, poultry by-product meal, blood meal and meat and bone meal have good potential for use in rainbow trout diets at high levels of incorporation.