Juvenile Tench Research Articles

Replacement of Dietary Fishmeal by Black Soldier Fly Larvae (Hermetia illucens) Meal in Practical Diets for Juvenile Tench (Tinca tinca)

The development of specific diets for the juvenile stage is a main target for culture intensification of tench (Tinca tinca). Aquafeeds still rely heavily on the use of fishmeal (FM) but concerns about economic and ecological sustainability make the use of alternative protein sources necessary. Insect meals are considered a promising substitute to replace FM. In a 90-day experiment, 6 diets with different replacement levels of FM by partially defatted black soldier fly larvae meal (BSFLM): 0%, 15%, 30%, 45%, 60% and 75%, were tested on juvenile tench. Survival rates were high (95.8–100%) without differences between treatments. Diet with 45% FM replacement allowed for best growth performance in terms of total length (TL = 66.4 mm) and weight (W = 4.19 g), without differences with 60% and 75% of replacement. A cubic relationship was evidenced between the level of FM replacement and growth. From the regression equations, the estimated optimal level of FM replacement was 47% (356 g BSFLM kg−1 diet). Externally visible deformities were always under 0.05%. The whole-body lipid content of the fish had a significantly negative linear regression with BSFLM (r2 = 0.80). The content of the essential amino acids (EAA) arginine, leucine, lysine, phenylalanine, methionine, and threonine in diets decreased with dietary BSFLM inclusion. However, it did not have a negative effect on growth performance, suggesting that EAA requirements were covered. The amount of essential amino acids in whole-body juveniles was similar independently of the diet provided. The results allow considering BSFLM as a sustainable protein source for juvenile tench feeding.

Fish Oil Replacement by Camelina (Camelina sativa L.) Oil in Diets for Juvenile Tench (Tinca tinca L.): Effects on Survival, Growth, and Whole-Body Fatty Acid Profile.

Tench (Tinca tinca L.) plays a key role in the diversification of inland aquaculture, but its culture is mainly based on extensive culture systems with usually low and unpredictable yields. Rearing procedures under controlled conditions are essential to promote and consolidate tench production, and it is necessary to set up adequate feeding in early growth phases. Fish oil (FO) is currently the main source of lipids in aquafeeds, but considering the stagnation of smaller pelagic fisheries, alternative oils should be addressed. In a ninety-day experiment, the effects of partial and total replacement of FO with camelina oil (CO) on juvenile tench growth performance and whole-body composition were evaluated. Six isonitrogenous and isolipidic diets with different levels of CO were tested: 0% (control), 20%, 40%, 60%, 80%, and 100%. The survival rate was 100%, and no significant differences in growth performance (total length, weight, specific growth rate, feed conversion ratio, and biomass gain) were found. The lipid content in whole-body juveniles was significantly lower when juveniles were fed diets containing 40% and higher levels of CO than those fed the control diet whereas linolenic acid content was significantly higher. No differences in ΣSFA, ΣMUFA, ΣPUFA, Σn - 3, or Σn - 6 whole-body content were found. The nutritional indices ΣPUFA/ΣSFA and Σn - 6/Σn - 3 showed a linear increase trend with dietary CO inclusion whereas the EPA + DHA showed an opposite tendency. Compared to the control diet, EPA + DHA content (g kg-1) was significantly lower in juvenile tench fed a 100% CO diet, and Σn - 6/Σn - 3 was significantly higher in juvenile tench fed 80% and 100% CO diets. Overall, the results indicate that the total replacement of FO with CO in diets is feasible without negative effects on growth performance whereas the nutritional quality of juvenile tench was unaffected with a maximum replacement of 80%.

Fish Oil Replacement by a Blend of Vegetable Oils in Diets for Juvenile Tench (Tinca tinca Linnaeus, 1758): Effects on Growth Performance and Whole-Body Composition.

Simple SummaryFish oil (FO) can be totally replaced by a blend of vegetable oils (30% linseed oil, 20% corn oil, and 50% olive oil) in diets for juvenile tench (Tinca tinca Linnaeus, 1758) without negative effects on survival rate and growth performance. Diets affected the composition of juveniles so that lipid content was significantly lower in animals fed diets without FO. Moreover, the content of linolenic acid (18:3n-3) increased as FO substitution did, being significantly higher with respect to control diet (without vegetable oils) from 40% or higher FO replacement diets. No differences in saturated, monounsaturated, and polyunsaturated fatty acids were found in the fish whole-body. Nutritional indices can be considered within optimal values for healthy foods.Among freshwater species, tench (Tinca tinca Linnaeus, 1758) is considered as a promising species for the diversification of aquaculture, but the intensification of techniques is necessary to promote and consolidate its culture. Adequate feeding in early growth phases is essential to face further grow-out. Fish oil (FO) is the main source of lipids in fish diets, but its production is unsustainable, and thus, alternative oils should be considered. A 90-day experiment was performed to evaluate the effects of partial and total replacement of cod liver oil (FO) by a blend of vegetable oils (VO) in juvenile tench. Six isonitrogenous and isolipidic diets with different levels of a VO blend containing 30% linseed oil, 20% corn oil, and 50% olive oil were tested: 0% (control), 20%VO, 40%VO, 60%VO, 80%VO, and 100%VO. With all diets, survival was 100%, and there were not differences in growth performance (total length (TL); weight (W); specific growth rate (SGR); feed conversion ratio (FCR); and biomass gain (BG)). Compared to the control group, whole-body lipid content decreased significantly in the 100%VO group. No differences in total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were found in the whole-body. The content of linolenic acid (ALA) in the whole-body increased as FO substitution did, being significantly higher with respect to control diet from 40% FO replacement diets. Nutritional indices, such as ΣPUFA/ΣSFA and Σn-6/Σn-3 ratios, tended to increase with increasing VO content, whereas the EPA + DHA showed an opposite trend. A total replacement of FO by the blend of VO did not affect the growth performance and fatty acid profile of juvenile tench. Further research on the effects of VO diet on nutritional quality in tench reared to commercial size should be performed.

Juvenile tench ( Tinca tinca L.) response to practical diets with different replacement levels of fish meal by pea protein concentrate supplemented with methionine

The effects of methionine supplementation in diets with different replacement levels of fish meal (FM) by pea protein concentrate (PPC) on survival, growth performance and body composition of juvenile tench (0.39 g of initial weight) were studied in a 90-day experiment. Six practical diets (50% crude protein) differing in replacement level of FM by PPC were tested: 0% (control diet), 35%,45%, 60%, 75% or 85%, corresponding to 0, 285, 366, 487, 608 and 685.4 g PPC kg−1 diet respectively. To provide the same amount as in control diet, methionine was included from the 45% substitution level. Survival rates were high, between 93.7% and 100%, without differences among treatments. Juveniles fed 75% and 85% of replacement diets showed lower (p < 0.05) weight and specific growth rate, which cannot be attributed to methionine deficiency. In all treatments, percentages of fish with externally visible deformities were low (under 0.1%). The increase in PPC diet content resulted in a significant reduction of lipid content in whole-body juvenile. Minimum methionine requirements for juvenile tench could be estimated in 10 g kg−1 diet and supplementation over this amount would be not necessary. Juvenile tench exhibited a high tolerance to PPC dietary content, up to 487 g kg−1, without affecting growth performance, which make possible to consider this vegetal source of protein as a suitable substitute to FM.

Growth and feed utilization of juvenile tench (Tinca tinca L.) given diets in which soy protein concentrate replaces fishmeal and methionine and arginine are used as amino acid supplements

ABSTRACT A 90-day experiment was conducted with four-month-old juvenile tench to test seven diets differing in replacement level of fishmeal (FM) by soy protein concentrate (SPC): 0% (control diet), 45%, 55%, 65%, 75%, 85% or 100% corresponding to 0, 312, 383, 451.6, 521.7, 590 or 695 g SPC kg−1 diet, respectively. Methionine and arginine supplementation was included from substitution levels of 55% and above to reach similar values to those provided by the control diet. Survival rate was close to 100%. The highest total length (TL) and weight (W) were reached with the control diet without significant differences from 45% to 55% diets. Significant lower TL, specific growth rate and daily increment in total length were obtained with 65% or higher replacement levels. The percentages of fish with externally visible deformities ranged from 0% to 9.3%, being higher with 75%, 85% and 100% replacement diets.

Dietary supplementation with Lactobacillus plantarum and β-glucan affects immune parameters in the tench (Tinca tinca) fry.

The aim of the experiment was to examine the effect of a diet enriched with Lactobacillus plantarum and/or β-glucan on the immune parameters in the juvenile tench (Tinca tinca). Fish were fed for 14 days different diets (phase 1 of the experiment), a dry commercial starter feed in the control group or the same feed supplemented with: 1% β-1,3/1,6-glucan in group G, 108 cfu L. plantarum g-1 in group L, 1% β-1,3/1,6-glucan + 108 cfu L. plantarum g-1 in group G+L. During consecutive 14 days all fish were fed the commercial feed alone (phase 2). The stimulating effects of the tested preparations was evaluated twice, at the end of each experimental phase. Dietary supplementation of β-1,3/1,6-glucan considerably improved the humoral innate immune response (activity of lysozyme and total Ig) and the pinocytotic activity of phagocytes. Supplement of L. plantarum improved the ability of the head kidney phagocytes (RBA) to carry out oxygen burst in L and G+L groups. A similar effect was observed for the killing activity of phagocytes (PKA) from the head kidney after the stimulation of A. hydrophila, and the effect persisted for two weeks after the commercial feed regime was resumed. A significant increase in the proliferative activity of B lymphocytes originating from the head kidney was observed in groups L and G+L. The study has revealed that the addition of the tested G+L synbiotic to dry diet stimulates the innate immune response mechanisms in the juvenile tench.

Effects of temperature on body chemical composition and incidence of deformities in juvenile tench, Tinca tinca (Actinopterygii: Cypriniformes: Cyprinidae), fed a commercial dry diet and/or natural food

Effects of temperature on body chemical composition and incidence of deformities in juvenile tench, Tinca tinca (Actinopterygii: Cypriniformes: Cyprinidae), fed a commercial dry diet and/or natural food

Diet and water temperature affect growth and body deformities in juvenile tenchTinca tinca(L.) reared under controlled conditions

The experiment was designed to determine the combined effect of fish diet and water temperature on juvenile tench Tinca tinca (L.). Three diets were used: commercial dry diet for fish Aller Futura (diet F); frozen Chironomidae larvae (diet C); and Aller Futura substituted with Chironomidae at a ratio of 3:2 (dry weight; diet FC). Daily food rations and duration of the experiment were adjusted to temperatures of 20°C, 23°C and 26°C based on a correction factor q equal to 1.000, 0.779 and 0.609 respectively. The experiment lasted 92, 72 and 56 days for the respective temperatures. No mortality occurred. The highest relative growth rates were found at 26°C in diets F and FC. The lowest food conversion ratio of 1.12–1.22 (recalculated for dry weight of feed diet) was determined in fish fed diet F at 23°C and 26°C. A high value of condition index appeared to be the early warning of decreasing biological quality of fish and deformities. The lowest incidence of fish with deformities (IDef) was found in groups fed diet C (<1%), while the highest (90%) in fish fed diet F at 26°C. A lower share of dry diet in the fish food and a lower water temperature led to a lower IDef. Thus, amount of dry feed in fish diet was the major factor inducing body deformities, while water temperature only modified the effects of the dietary factor. Diet C at 23–26°C was the most cost-effective of the tested combinations of diet and temperature.

Evaluation of pea protein concentrate as partial replacement of fish meal in practical diets for juvenile tench (Tinca tinca L.)

The aim of this study was to evaluate different replacement levels of fish meal (FM) by soy protein concentrate (SPC) on survival, growth performance and body composition of juvenile tench (Tinca tinca). A 90-day experiment was conducted with 5 month-old juveniles (31.95 mm total length, 0.396 g weight). Eight practical diets (50% crude protein) differing in the level of replacement of FM protein by SPC protein were tested: 0% (control diet), 25%, 35%, 45%, 55%, 65%, 75% or 100% corresponding to 0, 159, 222, 285, 348, 412, 475 or 634 g SPC kg -1 diet, respectively. Survival rate was 100% for all diets. Significant differences were not found (P>0.05) in growth values among 25%, 35% or 45% replacement diets and the control diet. At higher replacement levels (from 55% to 100%), fish had significantly lower growth (P<0.05). Fish fed from 0% to 45% replacement diets had significantly lower (P<0.05) feed conversion ratio and higher (P<0.05) protein productive value than those fed diets with higher replacement levels. The percentages of fish with externally visible deformities ranged from 1.1% to 4.4%. The relation among amino acid profiles of the diets, body composition, growth performance of juveniles and amino acid requirements of other fish species are discussed. Up to 285 g SPC kg -1 diet can be included in diets for juvenile

Effect of dietary lipid level on survival, growth performance and body composition of juvenile tench (Tinca tinca L.) fed practical diets

A 90-day experiment was conducted to evaluate the effects of practical diets with different lipid contents on survival, growth performance and whole-body composition of juvenile tench (Tinca tinca). Five-month-old juveniles (34.48 ± 0.77 mm total length, 0.382 ± 0.08 g weight) were fed practical diets with different lipid contents: 6.5%, 8.5%, 10%, 12%, 14%, 15.5% or 18%. Survival rates ranged from 96.7% to 100%. The highest growth was obtained with diets containing 8.5, 10 and 12% lipid. The five intermediate lipid contents (between 8.5% and 15.5%) caused lower FCRs (1.27–1.38). The percentages of fish with externally visible deformities were around 12%, with no significant differences due to the dietary lipid level. The relation among fatty acid profiles of the diets, body composition, growth performance of juveniles and requirements of other fish species is discussed.

Evaluation of poultry by-product meal as partial replacement of fish meal in practical diets for juvenile tench (Tinca tinca L.)

The aim of this study was to evaluate different replacement levels of fish meal (FM) by poultry by-product meal (PBM) on survival, growth performance and body composition of juvenile tench (Tinca tinca). A 90-day experiment was conducted with 5 month-old juveniles (31.95 mm total length, 0.396 g weight). Eight practical diets (50% crude protein) differing in the level of replacement of FM protein by PMB protein were tested: 0% (control), 25%, 31%, 37%, 43%, 49%, 55% and 61% corresponding to 0, 184.8, 229.2, 273.5, 317.8, 362.1, 406.5 or 450.8 g PBM kg−1 diet respectively. Significant differences were not found (P > 0.05) between 25% replacement of FM protein by PBM protein (184.8 g kg−1 PBM in diet) and control diet. At higher replacement levels, fish had significantly lower growth, higher feed conversion ratio and lower protein productive value (P < 0.05). Fish with externally visible deformities ranged from 1.1% to 3.3%. The relation among amino acid profiles of the diets, body composition, growth performance of juveniles and amino acid requirements of other fish species is discussed. Up to 184.8 g PBM kg−1 diet can be included in diets for juvenile tench without impairing growth performance.

Effects of different photoperiod conditions on juvenile tench (Tinca tinca L.) under intensive rearing

Summary Two 120-day experiments with 5-month-old juvenile tench (Tinca tinca L.) were conducted to evaluate different photoperiod conditions. In the first experiment, juveniles were exposed to natural winter photoperiod (ca. 11 h light: 13 h dark), continuous light or continuous darkness. In the second experiment, two photoperiods were tested: natural winter or an extended photoperiod (16 h light: 8 h dark). In all cases, survival was high (95.8–100%). In the first experiment, tench under the natural winter photoperiod had the highest growth (52.3 mm TL, 1.84 g W, 1.28% d−1 SGR). In the second experiment, the extended photoperiod enabled a significantly higher growth (56.8 mm TL, 2.51 W g, 1.75% d−1 SGR) than in the natural winter photoperiod. Percentages of deformed fish ranged from 1 to 31.2%.

Evaluation of different qualities and preparations of decapsulated Artemi a cysts as dietary supplement for juvenile tench (Tinca tinca L.)

Journal of Applied IchthyologyVolume 30, Issue s1 p. 40-43 Short Communication Evaluation of different qualities and preparations of decapsulated Artemia cysts as dietary supplement for juvenile tench (Tinca tinca L.) V. García, Corresponding Author V. García Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, Spain Author's address: Vanesa García, Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, E-24071 León, Spain. E-mail: [email protected]Search for more papers by this authorJ. D. Celada, J. D. Celada Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorÁ. González-Rodríguez, Á. González-Rodríguez Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorJ. M. Carral, J. M. Carral Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorM. Sáez-Royuela, M. Sáez-Royuela Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorR. González, R. González Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorÁ. González, Á. González Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this author V. García, Corresponding Author V. García Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, Spain Author's address: Vanesa García, Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, E-24071 León, Spain. E-mail: [email protected]Search for more papers by this authorJ. D. Celada, J. D. Celada Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorÁ. González-Rodríguez, Á. González-Rodríguez Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorJ. M. Carral, J. M. Carral Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorM. Sáez-Royuela, M. Sáez-Royuela Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorR. González, R. González Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this authorÁ. González, Á. González Departamento de Producción Animal, Facultad de Veterinaria, Universidad de León, Campus de Vegazana León, León, SpainSearch for more papers by this author First published: 24 May 2014 https://doi.org/10.1111/jai.12432Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume30, Issues1Special Issue: Proceedings of the VIth International Workshop on Biology and Culture of the Tench (Tinca tinca Linnaeus, 1758)June 2014Pages 40-43 RelatedInformation

Effects of varying protein level in practical diets on survival, growth, feed utilization and body composition of juvenile tench (Tinca tinca L.)

The aim of this study was to evaluate the effects of practical diets with different protein content on survival, growth, feed utilization and body composition of juvenile tench (Tinca tinca). A 90-day experiment was conducted with 6-month-old juveniles (34.35 mm total length, 0.411 g weight). Six practical diets differing in the protein level were tested: 40, 44, 48, 52, 56 or 60 %. Survival rates ranged from 96.7 to 100 %. The 52 % protein enabled the highest growth (55.49 mm total length, 2.11 g weight, 1.80 % day−1 specific growth rate) and the lowest feed conversion ratio (1.61) without significant differences (P > 0.05) from the 48 %. Protein productive value ranged from 15.64 to 22.01. The percentages of fish with visible deformities ranged from 1.1 to 4.4 %. The relationship among amino acid profiles of the diets, growth of juveniles, body composition and amino acid requirements of other fish species is discussed. Second-order polynomial regression analysis showed that the optimum dietary protein requirement for maximum growth of juvenile tench may be 52.7 %.

Production effect of different commercial feeds on juvenile tench (Tinca tinca L.) under the intensive rearing conditions

Feeding experiment with juvenile tench was focused on evaluation of production effect of three different commercial feeds with differentiated level energy and protein (Karpico Crumble Excellent Ex, Dan Ex 1352, Pro Aqua Brutfutter). In the 42-day experiment at 26 °C, commercial starters were fed intensively to tench of initially 18.92 mm mean total length and 69.41 mg individual mean body weight. Main monitored indices were – survival rate (%), individual body weight (mg) and specific weight growth rate (%.d−1). The best result was achieved with commercial starter Pro Aqua Brutfutter – mean individual body weight 483.38 mg, specific weight growth 4.44 %.d−1 and survival 99.1 %. Increasing level energy and protein increased production parameters of juvenile fish.

Evaluation of a practical diet for juvenile tench (Tinca tinca L.) and substitution possibilities of fish meal by feather meal

A basal diet for juvenile tench (Tinca tinca) was formulated and used to test possibilities of replacement of fish meal (FM) by feather meal (FeM). A 120-day experiment was conducted with 5 month-old juveniles (27.45mm total length, 0.308g body weight). Three diets (500g crude protein/kg) differing in the level of replacement of FM protein by FeM protein were prepared: 0 (basal diet), 0.25 (148g FeM/kg) or 0.35 (210g FeM/kg). Survival ranged from 0.96 to 0.97 (P=0.061). The basal diet enabled higher growth (59.3mm total length, 2.6g body weight, 1.74%/d specific growth rate; P<0.001) and lower feed conversion ratio (1.36; P=0.032) than the FeM diets. There were not significant differences in body weight and specific growth rate between 0.25 or 0.35 replacement of FM protein by FeM protein. The basal diet enabled satisfactory performance and low proportion of deformed fish (0.03), showing to be feasible for future studies on juvenile tench. The FeM inclusion at the levels tested reduced growth and increased the proportion of deformed fish.

Response of juvenile tench (Tinca tincaL.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90-day trial with 5-month-old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.

Impact of feeding juvenile tench (Tinca tinca (L.)) feeds supplemented with vegetable oils on hematological indexes and liver histology

The aim of the study was to identify the impact of feeding juvenile tench commercial feed supplemented with fish oil, linseed oil, arachide oil, and rapeseed oil on the hematology, cytology, and histology indexes of the liver. The fish were reared in a recirculating system and fed feed containing 470 g protein kg -1 feed and 120 g fat kg -1 feed (1000 g of base feed containing 70 g fat kg -1 feed was supplemented with 50 g of additional fat, i.e., fish oil (FO) or vegetable oils - linseed oil (LO), arachide oil (AO), or rapeseed oil (RO)). Statistically significant inter-group differences were noted for hematocrit (Ht), hemoglobin (Hb), red blood cell (RBC) counts, and other red blood cell indexes, including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) (P < 0.05). The lowest Ht and Hb values were noted in fish fed feed supplemented with fish oil (group FO), while the highest was noted in the tench from group AO. These differences were mainly caused by the occurrence of smaller erythrocytes in the peripheral blood of the fish from the FO group. No pathological changes were observed in the blood cells, which was in contrast to the parenchymal cells of the liver. Congestion, lipid vacuolization in hepatocytes, regressive changes in cytoplasm density, nuclear chromatin, and nucleus disintegration were observed in all fish. These changes were more pronounced in groups LO and AO. The fish from these groups were characterized by smaller hepatocytes and significantly higher nucleocytoplasmic ratios (P < 0.05).

Detoxifying response in juvenile tench fed by selenium diet

The effects of a selenium (Se) diet (1.0 mg Se kg −1) were investigated on growth, accumulation and antioxidant response in juvenile Tinca tinca at three endpoints (0, 4 and 8 weeks). Growth and condition factor ( K > 1.5) for both control (0.25 mg Se kg −1) and Se tench were not significantly affected. Se exposed fish exhibited the highest Se level in the kidney and the liver after 4 weeks. By feeding more Se the accumulation capacity of tench did not increase and a plateau, mainly for the liver, was thus reached. Se level remained almost constant in the muscle if compared to own control and for each endpoint. Superoxide dismutase activity in both tissues was not affected by Se supplementation and the higher catalase level in the kidney might support the hypothesis that the enzyme was adequate to remove the hydrogen peroxide production following Se exposure. However, supplemented diet with higher Se level could be critical for tench, as it may cause a lowering of glutathione peroxidase and glutathione reductase activities facilitating the onset of oxidative damage. The enhancement of thiol level and glutathione S-transferase activity, mainly in the liver, could be the signals of the only protection against the oxidative damage induced by Se.

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

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