Search

This study was undertaken to investigate the effects of sustained swimming exercise on the growth performance, muscle cellularity and flesh quality of juvenile qingbo fish ( Spinibarbus sinensis ). Experimental fish were exercised under four water velocities, nearly still (control, 3 cm s − 1 ) and 1, 2 and 4 body lengths (bl) s − 1 , for eight weeks at 25 °C. Then, growth performance indicated by the specific growth rate (SGR), white muscle cellularity suggested by the diameter and density of white muscle fiber, flesh quality evaluated by some textural mechanical properties (hardness, springiness, chewiness, cohesiveness) and physico-chemical parameters (pH, color, moisture, ash, protein, fat, amino acids, and fatty acids) were measured. Sustained swimming at moderate velocities (1 and 2 bl s − 1 ) resulted in a significantly higher SGR and similar white fiber diameter and density compared with the controls. However, the fish trained at a water velocity of 4 bl s − 1 displayed a similar SGR, smaller white fiber diameter and higher white fiber density compared with the controls. Sustained swimming resulted in significant increase in the values of pH and all textural traits but showed no significant effect on the color of the flesh for juvenile S. sinensis . Fish swimming under moderate water velocities exhibited higher levels of the protein content of the muscle, total essential amino acids (∑ EAA) (at 2 bl s − 1 ) and total amino acids (∑ AA) (at 1 and 2 bl s − 1 ) compared with control fish. However, the lowest levels of total amino acids (∑ AA) and total n-6 poly-unsaturated fatty acids (∑ n-6 PUFA) were observed in fish swimming at water velocity of 4 bl s − 1 . These data suggest that (1) moderate swimming exercise (1 or 2 bl s − 1 ) improved growth performance, which could not be attributed to changes in white muscle cellularity; (2) sustained swimming showed a positive effect on texture characteristics, which was partly due to the higher white fiber density and flesh pH compared with controls; and (3) moderate swimming exercise (1 or 2 bl s − 1 ) was beneficial for improving the nutritional quality of the flesh, whereas high-intensity swimming (4 bl s − 1 ) resulted in an impairment of the nutritional quality of the flesh in juvenile S. sinensis . Statement of relevance We declare that the experiments complied with the current laws of the country in which the experiments were performed and that our paper complied with the laws of commercial aquaculture. [ABSTRACT FROM AUTHOR]

Skeletal muscle growth and flesh quality were evaluated in Senegalese sole fed plant protein (PP) diets. A control fish meal-based diet (FM) was compared with three isonitrogenous (54%) and isolipidic (9%) diets with increasing levels of PP blends (50% PP50, 75% PP75 and 100% PP100). By the end of the experiment sole fed PP50 and PP75 had a body length similar to the CTR (25 cm), but fish fed PP100 were significantly smaller (23 cm). Total FM replacement (PP100) resulted in significantly smaller muscle cross sectional area mainly due to a decrease in the muscle fibre size as the total number of fibres did not vary significantly among treatments. The dietary incorporation of PP significantly reduced the expression of several key genes involved in myogenesis and muscle growth (mrf4, fgf6, myhc and mylc2). Fillet texture was affected by the total substitution of FM. Fish fed PP100 diet had a significantly higher modulus of elasticity (lower flesh stiffness) compared with the other groups. Muscle fibre size was moderately related (r = 0.573) to the modulus of elasticity and positively correlated with the expression of lysyl oxidase (r = 0.495). Muscle cellularity changes were not associated with the expression of texture-related genes (capn2, ctsb, ctsd), since no significant differences were observed among diets. The present results point towards a modulation of the expression of several muscle growth related genes by increasing levels of PP sources that alter muscle cellularity and textural properties of Senegalese sole when total FM is replaced by PP. Statement of relevance The biological basis through which sustainable and practical plant protein diets (PP) affect flesh texture determinants is extremely scarce so the present results will be valuable to the aquafeed industry, fish producers and final consumers. This study clearly shows that PP diets reduced expression of several key genes involved in myogenesis and muscle growth and can hence affect fish growth potential at long term. This study identifies useful markers that correlated well with muscle cellularity and muscle growth and can be further used to select the most appropriate diets for a fish species. [ABSTRACT FROM AUTHOR]

We examined the effects of partial dietary supplementation with wild zooplankton or fish protein hydrolysate on cod production traits, and how they related to the expression of growth and appetite regulating transcripts and muscle cellularity. Atlantic cod larvae were fed three different diets: enriched rotifers and Artemia (RA); RA + fish protein hydrolysate (RA-PH); and RA supplemented with 5–10% wild zooplankton (RA-Zoo). Partial supplementation with zooplankton significantly improved cod dry weight at 60 days post-hatch (by approximately 4-fold), specific growth rate (by 2.5% day − 1 ) and the general development of cod larvae. Although the zooplankton fed cod were still larger at approximately 1.5 years of age, the growth advantage of this group decreased with age (the difference in wet mass decreasing from approximately 30% at 0.5 years old to 11% at 1.5 years old). In contrast, the protein hydrolysate enrichment did not improve growth, had a negative effect on survival, and increased the incidence of external deformities in 1.5 year old fish. The growth enhancement observed in the RA-Zoo larvae was largely unrelated to differences in the transcript levels of several important growth [Insulin-Like Growth Factor 1 ( igf-1 ); igf-2 ; Growth Hormone ( gh ); GH Receptor-1 ( ghr-1 ); ghr-2 ; and myostatin ( mstn )] or appetite regulating genes [Cocaine and Amphetamine Regulated Transcript ( cart) and Neuropeptide Y ( npy )], but was associated with an increase in the number and size of skeletal muscle fibers. Our findings suggest that incorporating small amounts of wild zooplankton into larval feeding regimes may significantly enhance the production of marine fishes, but that the transcript levels of the above hormones and hormone receptors are not valuable biomarkers of growth in cod larvae. Statement of relevance This research shows that small amounts of zooplankton significantly improve the growth of Atlantic cod larvae, and thus, that cultured zooplankton may be a viable and cost-effective strategy for increasing the growth (and potentially health) of intensively cultured marine finfishes. [ABSTRACT FROM AUTHOR]

A high frequency of cannibalism and high variability of growth rate within the same larval batch are the main bottlenecks for implementation of meagre culture. In this study the effect of two sodium alginate-encapsulated diets containing 55 (control) and 68% protein was tested in terms of larval composition, survival, growth and muscle cellularity. The results showed that the diet with higher protein content improved larval survival but no differences on larval growth were observed between treatments. Diets did not affect the amino acid and fatty acid profiles of meagre larvae. The differences between larval fatty acid profiles were mainly related to larval age rather than treatments. Meagre larvae fed the high protein diet showed a higher frequency of white muscle fibres with an area smaller than 150 μm 2 and a lower mean fibre area (214.9 ± 160.6 μm 2 and 187.88 ± 162.7 μm 2 , for 55 and 68% of protein, respectively). These results suggest that a higher dietary protein increases meagre larval survival and leads to a potential higher contribution of fibre hyperplasia. Statement of relevance The main aim of this work was to test two diets containing different protein levels (55 and 68%) and determine its effect on larval survival, growth, larval composition and muscle cellularity. This work was carried because meagre has been thought to have a higher protein requirement compared to seabream and seabass (Amoedo, 2011). Nevertheless, meagre is usually fed on diets formulated specifically for seabream suggesting that meagre protein requirements are not being satisfied and meagre growth might be constrained. Given that meagre is the species with highest potential to be intensively farmed in the Mediterranean region it is important to formulate specific diets for this species. The results obtained in this work showed that although growth was not affected by the diet, there seems to be a higher potential for growth in the long-term as fibre recruitment was higher when larvae were fed a high protein diet. [ABSTRACT FROM AUTHOR]

In the present study, Senegalese sole eggs incubated at 20°C were reared at three different temperatures (15°C, 18°C or 21°C) during the pelagic phase, and then transferred to a common temperature (20°C) from benthic stage until 100days post-hatch (dph). Somatic growth, fast muscle cellularity and expression of 15 growth-related genes were compared at the same developmental stage for each temperature (pre-metamorphic larvae, metamorphic larvae, post-metamorphic larvae) and at 83dph and 100dph early juveniles. During pre-metamorphosis and metamorphosis, larvae from 21°C weighed significantly more than those reared at 18°C or 15°C (P <0.001). Relative growth rate (RGR) of pelagic larvae and survival of newly-settled larvae were also higher at 21°C (P <0.05). Furthermore, an increase in muscle growth towards the highest temperatures was observed concomitantly with an increase in gene expression, namely myogenic regulatory factors (MRFs), myosins, igf-I and fgf6. After transfer to a common temperature (20°C), the 15°C group initiated a process of compensatory growth, inverting relative growth rate values that became the highest, particularly between 83dph and 100dph (P <0.05). This increased growth effort in the 15°C group was accompanied by an up-regulation of gene expression in fast muscle, particularly in the 83dph juveniles. Mrf4 and myHC were up-regulated at 15°C and positive correlations with growth were also found for myog or pax7 (P <0.05). In contrast, mstn1 was down-regulated at 15°C (P <0.05), suggesting a boost in muscle growth. By 100dph, the 15°C group had already reached the same weight as the 18°C and the same length as the 21°C ones. At this age, the 18°C juveniles had the largest mean muscle fibre diameter (P <0.001), and thus fibre hypertrophy seems to be a major growth mechanism relatively to the other groups. Our work shows that temperature during pelagic phase greatly influences the growth trajectory of Senegalese sole juveniles. [ABSTRACT FROM AUTHOR]

The 8-week rearing trial was conducted to estimate the effect of dietary hydroxyproline (Hyp) supplementation on growth performance, amino acid profiles, fatty acid profiles, and collagen concentration in muscle samples, liquid holding capacity (LHC), pH, cooking loss and antioxidant activities in flesh of post-mortem, histomorphology, ultrastructure and molecular expression of muscle samples, and raw- and cooked-fillet texture characteristics of Yellow River carp (Cyprinus carpio haematopterus). Six isoproteic and isolipidic practical diets were formulated to contain graded levels of Hyp (1.36, 3.93, 7.14, 8.86, 11.45 and 13.69 g/kg of dry matter). A total of 840 carps with an average initial weight of 17.90 ± 0.28 g were randomly allocated to 24 polypropylene tanks with funnel-shaped bottom (400 L capacity filled to 300 L and 35 fish per tank). The results showed that no significant differences were found in growth performance and morphology parameter among all treatments (P > 0.05). With the increase of dietary Hyp levels, the glycine (Gly) content, and the proportion of 22:6n-3, n-3 PUFA and collagen concentration in carp fillet showed a significant ascending tendency, while arginine and proline were in downtrend (P < 0.05). Liquid loss, lipid loss and cooking loss were significantly decreased with the increasing dietary Hyp levels (P < 0.05), and the pH values in muscle samples of carp fed with dietary Hyp (> 3.93 g/kg) were significantly higher than that in control group (P < 0.05). Dietary Hyp supplementation improved the antioxidant properties of hepatopancreas and muscle with the increasing dietary Hyp levels (P < 0.05). Overall, we posed that appropriate dietary Hyp supplementation can promote myogenesis and collagen synthesis in muscle of carp, ultimately improved the raw- and cooked-fillet texture characteristics. The current research will be contributed to find an efficient way to ensure predictable and firmer texture of farmed Yellow River carp. • Dietary Hyp promoted the synthesis of glycine and Lc-PUFA in flesh. • Dietary Hyp promoted the antioxidant properties of hepatopancreas and muscle. • Dietary Hyp improved flesh pH, LHC, cooking loss and the collagen content, and fillet texture. [ABSTRACT FROM AUTHOR]

Abstract: Muscle characteristics that are important for flesh quality traits were assessed in populations of wild and farmed Atlantic salmon (Salmo salar L.). The wild fish were obtained from a commercial fishery on the North Esk, Scotland in 2001 and 2003. The farmed fish comprised 7families from the Stofnfiskur breeding programme (Stofnfiskur A/S, Iceland) grown in 5m×5m×5m net pen sea cages in a dedicated trial unit on South Uist, Scotland. Total carotenoid pigment (mgkg−1 wet mass flesh) concentrations were higher in farmed (7.68 and 8.43 for grilse and salmon, respectively) than wild fish (5.53 and 6.44 for grilse and salmon, respectively). In contrast, the average flesh colour, measured with a SalmonFan™, was similar for all groups (27.4 to 28.0), indicating a superior colour visualisation per unit pigment concentration in wild fish. The flesh lipid content was 46%-higher (grilse) and 84%-higher (salmon) in farmed than wild fish. Vitamin E concentrations per unit wet mass lipid were similar in wild and farmed salmon and in the range (208–259mgkg−1). Fillet firmness was measured using a shear test and instrumental texture analyser. The work done (WD) to shear standardised post-rigor muscle samples was higher in grilse than salmon and was significantly greater for the wild (710 and 811mJ, respectively) than farmed (415 and 602mJ, respectively) fish, indicating a firmer texture in the wild fish. The grilse and salmon sampled had stopped recruiting fast muscle fibres and both wild and farmed fish had around 650,000fibres per trunk cross-section. Thus differences in fillet texture and colour between these populations could not be explained by the muscle cellularity which was similar between groups. Hydroxyproline (HYP) was used to estimate collagen concentration. Alkaline-insoluble HYP was 72.5% higher in wild than farmed salmon (14.0 vs. 8.1μmolg−1 dry mass, respectively) whereas alkaline-soluble HYP was 5.2-fold higher in farmed than wild salmon (31.0 vs. 6.0μmolg−1 dry mass, respectively). The alkaline-insoluble collagen fraction is thought to be enriched with reducible and non-reducible cross-linked collagen. There was a significant positive correlation between pyridinoline (PYD) crosslink concentration and WD, explaining 25% of the within population variation in firmness. However, PYD concentration (pmolg−1 dry mass) was similar between wild (476) and farmed (445) salmon and cannot explain the differences in flesh firmness observed between populations. It was hypothesised that the higher average values of firmness in the wild than farmed salmon flesh can in part be attributed to higher concentrations of reducible immature collagen crosslinks. [Copyright &y& Elsevier]

Abstract: Sea bass (Dicentrarchus labrax L.) has been widely farmed in the last decade. In order to a better understanding of the final quality of this species, muscle cellularity and quality parameters of the flesh were studied on 14 specimens of wild and 11 farmed Atlantic sea bass, at approximate commercial size (weight 350 g, length 32 cm). White muscle cellularity was evaluated by means of the following parameters: number and diameter of muscle fibres, as well as the muscle fibre size distribution, throughout the total cross-section of the flesh. To ascertain the flesh quality, several physico-chemical parameters (moisture, protein, total fat, fatty acids, hydroxyproline, collagen and pH) were analyzed, and textural mechanical properties (hardness, springiness, chewiness, cohesiveness, gumminess) were determined objectively with a texturometer. Muscle cellularity was different between both groups, such that muscle fibre density was higher for wild specimens (p &#60;0.05). Farmed sea bass showed a higher content of moisture and protein (p &#60;0.01), and a lower flesh pH, and hydroxyproline and collagen contents (p &#60;0.01). Despite of the fact that the total fat did not show significant differences between both populations, saturated and monounsaturated fatty acids were significantly higher in farmed than in wild sea bass, whereas wild fish showed a higher content of polyunsaturated fatty acids (p &#60;0.05). No significant differences were found in the total content of ω−3 fatty acids between both groups. All textural properties were significantly higher in wild than in farmed fish (p &#60;0.001), all of them show a positive and significant correlation with muscle fibre density, pH, hydroxyproline and collagen contents. Changes in these parameters determined marked differences in the flesh quality of wild and farmed sea bass, whereas no relationship was found between muscle cellularity and nutritional composition of the sea bass. According to our results, genetic factors as well as the influence of extrinsic factors such as feeding regimes and/or exercise may determine significant variations of some structural and flesh quality parameters of the sea bass. [Copyright &y& Elsevier]

Abstract: Mixed families of Atlantic salmon (Salmo salar L.) were subject to two photoperiods to produce accelerated and 1+ smolts in January and May 2001, respectively. The fish were reared in freshwater land-based tanks until October 2000 and then split into two groups: natural photoperiod (1+ smolts) and manipulated photoperiod (accelerated smolts). Fish were sorted into small and large grades and transferred to 12 sea cages at Gildeskål Research Station, Northern Norway (13°57′20ʺE, 67°04′10ʺN) in May–June 2001. The four groups were reared in triplicate cages until October 2002. The number and size distributions of fast myotomal muscle fibres were determined at the level of the first dorsal fin for all groups in May 2002 (selected fish of 2.4 kg) and October 2002 (randomly sampled fish). The presence of muscle fibres less than 10 μm diameter indicated active fibre recruitment in all groups in May 2002. Muscle fibre number had reached its maximum value (FNmax) in the October harvest. Analysis of variance revealed no significant difference in average values of FNmax (6.6×105±1.4×10 4), muscle fibre density (76.2±1.7 fibres mm−2 muscle) and fibre diameter (121.3±1.5 μm) between different photoperiod treatments (mean±S.E., n=66). Smoothed curves were fitted to the measurements of fibre diameter using a kernel function. Nonparametric Kolmogorov–Smirnov tests revealed no significant difference in the distribution of fibre size between accelerated and 1+ post-smolts. There were, however, significantly more muscle fibres in the large than small grade fish, probably reflecting genetic differences in FNmax. Flesh quality was assessed as fillet firmness using an instrumental texture method. The total work (J) required to shear muscle samples of standardized thickness showed no significant difference between photoperiod treatments. It was concluded that the manipulation of photoperiod required to produce accelerated smolts did not affect muscle cellularity and flesh firmness in post-smolts of a commercial harvest weight. [Copyright &y& Elsevier]

This experiment on farmed Atlantic salmon (Salmo salar L.) was designed to investigate the effect of postsmolt photoperiodic regime on growth performance, muscle cellularity, and flesh quality in out-of-season produced smolts. The offspring from three pairs of half-sibling crosses were studied to provide information on the genetic variability of treatment effects. In both treatments, parr were initially held on 10-h light/14-h dark for 6 weeks from the 27 September until the 8 November 2000, and then transferred to continuous light. All fish were transferred from fresh to salt water on the 12 January. In treatment A (TA), smolts were transferred from continuous light to ambient short days (23 January 2001), whereas in treatment B, (TB) smolts were continued on 24-h light until natural day length approached the seasonal maximum (1 June 2001). Fish were reared in outdoor saltwater tanks and transferred to 5×5×5 m sea cages at the Feed Trial Unit, Loch Duich, Scotland on the 21 April 2001. In the 6–9 months following smoltification, the growth performance of 835 fish held on continuous light (TB) was superior to that of 715 fish returned to short days (TA). Thereafter, in five out of the six families, growth performance was higher in TA than TB groups, such that the average bodyweight of families was no different between treatments over the production cycle. Bodyweight, however, showed significant family effects and a significant treatment×family interaction. The cellularity of the fast myotomal muscle was determined in a subset of fish sampled 2 weeks after the lights were switched-off in the TB groups (14 June 2001) and when a commercial harvest weight was achieved (5 September 2002). In June 2001, the average bodyweight was 80% higher, and the number of muscle fibres per myotomal cross-section was 43.5% greater in TB than TA groups. Muscle fibre recruitment was subsequently higher in the TA than TB groups such that the maximum fibre number (5.88×105) was similar between treatments. However, the density of fast muscle fibres (fibres mm-2 muscle cross-sectional area) remained 7.5% higher for TB (82.1±1.3, n=46) than TA (76.4±1.1, n=53) groups (mean±S.E.; P<0.05). Firmness was assessed in fillets 3 days postmortem using an instrumental texture method (TA-Hdi Texture Analyser, Stable Microsystems). The total work done to shear tissue samples (mJ) was 8.3% higher in TB (432±11, n=46) than TA (399±7, n=53) groups (mean±S.E.; P<0.05). At the family level, there was a significant correlation between the total shear work (Sw) and muscle fibre density (Fd), explaining 49% of the total variation. Individual growth (α) rate was investigated using a statistical model. For the relatively modest growth rates achieved in the trial, there was no significant correlation between α and either Sw or Fd. The concentration of muscle lipid was 9.1% higher in the TA (14.7% dry mass) than TB groups (13.3% dry mass). Muscle astaxanthin concentration was independent of treatment but showed significant differences between families. It was concluded that continuous light treatment immediately following seawater transfer produced small but significant effects on muscle growth over the production cycle resulting in a higher fibre density and a firmer flesh. The magnitude of such effects is likely to be critically dependent on the timing of the harvest. [Copyright &y& Elsevier]