Diets For Juvenile Nile Tilapia Research Articles

Impact of Tenebrio molitor larvae meal substituted for fish meal in diets for juvenile Nile tilapia (Oreochromis niloticus): Growth performance and feed efficiency

The aim of this study was to evaluate the effects of feeding Nile tilapiya juvenile (Oreochromis niloticus) with diets based on fish meal and Tenebrio molitor (TM) larvae meal on growth performance and feed efficiency. For this purpose, three diets were prepared: Control diet (FM); without T. molitor larvae meal, insect diet (TM); 100% of fish meal has been replaced by T. molitor larvae meal and mixture diet (FM/TM); 50% of fish meal has been replaced by T. molitor larvae meal. A total of three groups in three replications were used over the 46-day investigation. In the experiment, 1-month-old Nile tilapia juveniles were used, which were with an average weight of 0.12±0.001 g. At the end of the experiment, the best growth was in the FM group, then the TM group and the lowest growth was in the FM/TM group (P0.05). SGR was quite low in all groups. The overall feeding response was good and the experimental diets were well accepted by the fish. The best FCR was in the FM group. This was followed by the group fed the TM diet. However, statistically, the difference between them was not significant (P

Effects of Dietary Peppermint (Mentha piperita) Essential Oil on Growth Performance, Plasma Biochemistry, Digestive Enzyme Activity, and Oxidative Stress Responses in Juvenile Nile Tilapia (Oreochromis niloticus)

This study aimed to evaluate the supplementation of peppermint essential oil (Mentha piperita; PEO) in diets for juvenile Nile tilapia (Oreochromis niloticus). A feeding experiment with diets containing graded levels (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 g kg−1) of PEO was carried out with fish of 0.58 ± 0.08 g. The inclusion of graded levels of PEO in the diet improved the weight gain (0.52 g kg−1), feed intake (0.51 g kg−1), and feed conversion (0.51 g kg−1) of juvenile Nile tilapia in a quadratic pattern. Increasing levels of PEO also led to a linear decrease in body lipid content. The gut activity of the digestive enzymes amylase (0.54 g kg−1) and protease (0.39 g kg−1) increased quadratically, whereas lipase activity increased linearly. PEO increased the activity of the antioxidant enzymes catalase (CAT; 0.52 g kg−1) and superoxide dismutase (SOD; 0.58 g kg−1) while reducing the production of malonaldehyde (MDA; 0.40 g kg−1) and nitric oxide (NO; 0.63 g kg−1) in the liver. The results of this study provide evidence of the beneficial effects of PEO on the growth and health of Nile tilapia and recommend a dose of 0.6 g kg−1 as the optimal level of supplementation.

Substitution of fish meal with Madagascar cockroach (Gromphadorhina portentosa) meal in diets for juvenile Nile tilapia (Oreochromis niloticus): effects on growth, nutrient assimilation, and nitrogen turnover rates.

Among the wide variety of alternative ingredients aimed to substitute fish meal in aquafeeds, insect meals have been recently proposed as novel, nutritionally good dietary components. In the present study, five isoproteic and isoenergetic experimental diets formulated with varying dietary levels of Madagascar cockroach meal substituting fishmeal on a dietary protein basis (0, 25, 50, 75, and 100%) were supplied to.Nile tilapia juveniles (Oreochromis niloticus) for 29days. Production parameters were compared among treatments, and the relative assimilation of the dietary nitrogen supplied by fishmeal and insect meal was estimated. To this end, nitrogen stable isotope analyses were applied to diets and fish muscle tissue. The isotopic changes elicited by the experimental ingredients were used to estimate the time required to reach isotopic equilibrium, the nitrogen turnover rates, and nitrogen residency times in muscle tissue. The latter were short and ranged from 4.7 to 6.2 d, except in diet containing 100% cockroach meal (7.8 d). No statistical differences were detected in final mean weight, specific growth, and survival rates among treatments. The relative proportions of dietary nitrogen and total dry matter supplied by insect and fish meal to growth were similar to the established dietary proportions after these were corrected for their respective apparent digestibility coefficients. The cockroach meal present in diets containing both main ingredients supplied relatively high proportions of dietary nitrogen (from 16 to 69%) to the biosynthesis of fish muscle tissue.

Dietary glutamine improves growth and intestinal morphology of juvenile GIFT tilapia (Oreochromis niloticus) but has limited effects on innate immunity and antioxidant capacity

This study evaluated the effects of dietary glutamine (Gln) supplementation on growth, intestinal morphology, and health status of Nile tilapia juveniles. Four hundred forty GIFT tilapia juveniles (4.4 ± 0.1 g) were randomly distributed in 40 tanks (250-L) and fed five practical diets supplemented with graded levels of l-glutamine (0, 0.5, 1.0, 1.5, and 2.0% Gln) with eight replicate tanks/diet. The experimental diets were formulated to contain 29% digestible protein and 14.5 MJ kg−1 digestible energy. After 90 days of feeding, growth performance, intestinal morphology, and body proximate composition were evaluated. Additionally, eight fish per treatment were sampled for the assessment of hematological profile, antioxidant capacity and innate immune responses. Glutamine supplementation improved relative weight and length of the intestine, as well as villus length and villus:crypt ratio, which could be related to better feed efficiency observed in fish fed Gln-supplemented diets. Final body weight and weight gain also were positively affected by dietary Gln supplementation. Fish fed Gln-supplemented diets showed increased glutathione (GSH) concentrations in the intestine. However, Gln supplementation had no significant effects on hematological and biochemical parameters and presented limited effects on innate immune responses. In summary, dietary Gln supplementation improved growth, feed efficiency, and promoted Nile tilapia intestinal development and function. Based on polynomial regression analysis of growth performance parameters, the recommended level of Gln supplementation in diets for juvenile Nile tilapia was estimated to be 1.33% of dry weight. These results also imply that higher levels of Gln supplementation may be required to support enhanced immune responses and antioxidant capacity, but further studies are necessary to evaluate these latter notions.

Effects of microencapsulated probiotics-supplemented diet on growth, non-specific immunity, intestinal health and resistance of juvenile Nile tilapia challenged with Aeromonas hydrophila

The present study evaluated the use of two microencapsulated probiotic additives in extruded diets for juvenile Nile tilapia (Oreochromis niloticus). For this purpose, 630 juvenile tilapias were distributed in nine experimental units (70 fish per unit), conditioned to three treatments (SACCH with Saccharomyces cerevisiae; BACIL with Bacillus amyloliquefaciens and B. subtilis; and control), all in triplicate. Zootechnical, intestinal microbiota, haemato-immunological, as well as histological and histomorphometric analysis were performed. At the end of the experimental period, the fish were exposed to the pathogen Aeromonas hydrophila. After 45 days of dietary supplementation, we verified greater survival, improvements in feed conversion, as well as in the specific growth rate in fish that received diets containing probiotics. In the intestinal histomorphology, both probiotic treatments expressed greater length and width of the intestinal folds. Furthermore, a significant differentiation of intestinal microbiomes was observed between treatments in the metagenomic evaluation. In the experimental challenge against A. hydrophila both probiotic treatments showed lower cumulative mortality (10% SACCH and 15% BACIL) than the control (45%). We conclude that the use of probiotics, as presented in this study, microencapsulated in extruded diets for juvenile Nile tilapia improves the zootechnical and health aspects of fish, demonstrating probiotic action as an immunomodulator.

Corn substitution by mesquite bean flour (Prosopis juliflora) maintains growth and improves protein metabolism of Nile tilapia juveniles (Oreochromis niloticus).

The objective of this study was to evaluate the potential of mesquite bean flour (Prosopis juliflora) as an energy ingredient in extruded diets for juvenile Nile tilapia (Oreochromis niloticus). Two experiments were carried out: the first consisted of a study to evaluate the chemical composition and digestibility of the energy and nutrients of MBF; the second consisted of a growth test, in which juveniles consumed diets containing different proportions of corn substitution by MBF, in which zootechnical, hematological, physiological, and metabolic variables were evaluated. It was observed that MBF has a chemical composition similar to corn, as well as the apparent digestibility of energy and nutrients. The higher sucrose/starch ratio of the ingredient stands out, as well as the difference in digestibility (p < 0.05) between the predominant carbohydrates 87.63 and 99.25% for starch and sucrose, respectively. In the growth assay, no difference was observed between zootechnical variables (p > 0.05), and sucrase and alkaline phosphatase activities were increased (p < 0.05), which was not observed for amylase and lipase (p > 0.05). The hematological variables did not change (p > 0.05). Metabolic variables indicate a reduction in gluconeogenesis from amino acids, as can be seen by the reduction in liver transaminase levels (ALT and AST) and glutamate dehydrogenase (GDH), as well as the greater availability of free amino acids in plasmas (p < 0.05). Thus, it can be said that MBF has a high nutritional value and can totally replace corn in diets for juvenile tilapia and the metabolic findings indicate a potential protein-sparing effect.

The effects of açaí oil addition in tilapia diets on performance, hepatic energy metabolism enzymes and antioxidant responses

The aim of the present study was to determine whether açai oil (Euterpe oleraceae) addition in the diets of juvenile Nile tilapia (Oreochromis niloticus) in biofloc system would stimulate hepatic energy metabolism and antioxidant responses. Treatments are as follows: T0 (6%-soybean oil), T1 (1%-AÇAI; 5%-SOY), T3 (3% AÇAI; 3%-SOY) and T6 (6%-AÇAI). In the liver, reactive oxygen species levels were significantly lower in T1, T3 and T6 than in T0, lipid peroxidation levels were significantly lower in T3 and T6, and nitric oxide levels were significantly lower in the T6 than in T0. Glutathione peroxidase activity was significantly higher in the T3 and T6 than in T0, while superoxide dismutase activity and total antioxidant capacity levels were significantly higher in the T6 than in T0. Adenylate kinase activity was significantly lower in the T6 than in T0. These results suggest that the açai oil addition in Nile tilapia diets stimulated antioxidant responses.

Replacement of fishmeal with processed canola meal in diets for juvenile Nile tilapia (Oreochromis niloticus): Growth performance, mucosal innate immunity, hepatic oxidative status, liver and intestine histology

The present study was carried out to evaluate the effect of processed canola meal (PCM) as fishmeal (FM) substitute in juvenile Nile tilapia diet. Firstly, canola meal (CM) was dephytinized using 2000 IU/kg phytase and subjected to methanolic ammonia solution (MAS). Finally, five isonitrogenous and isoenergetic diets were formulated by inclusion of 0 (control), 12.5, 25, 37.5 and 50% PCM at the expense of dietary FM. Each experimental diet was fed to three randomly allotted groups of 17 juvenile Nile tilapia with an average body weight of 3.5 ± 0.1 g for 36 days. Fish were feed three times a day until apparent satiation. Results showed that there were no statistically significant differences regarding SGR, final body weight and WG between control group and PCM2 (i.e., diet with 25% PCM inclusion level) (p > .05); however receiving diets with higher PCM content (>25%) resulted in significantly decreased growth indices (p < .05). Meanwhile, FCR, FI and apparent digestibility coefficient of protein (ADCprotein) did not differ among experimental groups (p > .05). Digestive enzyme activities, mucosal innate immunity, liver antioxidant enzyme activities and liver tissue malondialdehyde content (MDA) were not significantly affected by dietary inclusion of PCM (p > .05). However, relative gene expression of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were significantly increased by dietary PCM content increment (p < .05). In line with growth performance, histological observations revealed that those fish received higher levels of dietary PCM content (i.e. 37.5 and 50%) showed intensive intestinal and hepatic mononuclear immune cell infiltration, lamina propria expansion and intestinal villus detachment and shortening (p < .05). In conclusion, despite containing lower glucosinolate, phytic acid, phenolic compounds and tannins well within the recommended thresholds for aquatic animals nutrition, diets containing PCM beyond 25% negatively affected the growth performance and intestine and liver tissue histoarchitecture of juvenile Nile tilapia. However, further complementary studies are needed regarding the effects observed on gut histology and expression of antioxidant enzyme genes.

Phosphatidylcholine in diets of juvenile Nile tilapia in a biofloc technology system: Effects on performance, energy metabolism and the antioxidant system

Intensification of aquaculture production systems requires more nutritionally complete diets to maximize productive performance, metabolic processes and overall fish health. In previous studies, dietary supplementation with choline (both choline chloride and phosphatidylcholine) improved productive performance of tilapia cultivated in clear water. Nevertheless, choline has not been tested in a biofloc technology system (BFT), a culture system inhabited by diverse microorganisms that serve as food sources for fish. The objective of this study was to determine whether supplementation with phosphatidylcholine, also known as vegetable choline (0, 400, 800 and 1200 mg/kg of feed), in diets of Nile tilapia (Oreochromis niloticus) in a biofloc system would stimulate energy metabolism and the serum antioxidant system, with consequent improvements in productive performance. Juvenile Nile tilapia (≅ 8 g) were tested over 40 days. During this period, zootechnical performance was evaluated. Blood, gills and liver were collected at the end of the experiment for biochemical and energetic analyses. There were no significant differences between the treatments with respect to parameters of zootechnical performance (body weight, biomass gain, feed conversion, specific growth rate and hepatosomatic index) (P > 0.05). Alanine aminotransferase levels were significantly lower in fish fed 800 mg/kg of phosphatidylcholine than in control; total protein levels increased as a result of increased globulin levels. Activities of creatine kinase enzyme (800 and 1200 mg choline/kg treatments) and pyruvate kinase (1200 mg choline/kg) were significantly higher in choline-treated fish than in controls. Supplementation with the three doses of choline reduced hepatic lipid peroxidation and stimulated glutathione S-transferase activity. By contrast, the activities of other antioxidant enzymes (catalase, glutathione peroxidase and superoxide dismutase) were altered in the livers of fish that consumed the highest doses of phosphatidylcholine. We conclude that, in a biofloc system, supplementation with phosphatidylcholine had no effect on the zootechnical performance of tilapia; however, it stimulated energy metabolism and contributed to activation of hepatic GST and lower levels of lipid peroxidation.

Valine in diets for juvenile Nile tilapia (Oreochromis niloticus): growth performance, chemical composition, blood parameters and skeletal muscle development

Valine belongs to the group of branched-chain amino acids, has an important structural role and is primarily deposited as body protein. The present study evaluated the effects of valine in diets of juvenile Nile tilapia. A total of 216 juveniles with weight of 21.40 ± 0.42 g and length of 10.07 ± 1.00 cm were distributed into 18 aquarium in a completely randomized design with six treatments and three replicates. Six diets containing 24.30% digestible protein, 3,100 kcal/kg digestible energy, and increasing valine levels (0.54; 0.63; 0.72; 0.81; 0.90; 0.99%) were prepared. The following factors were evaluated: performance, chemical composition, blood hematological and biochemical, and skeletal muscle development. Differences were observed in productive performance between treatments for weight gain, daily weight gain and apparent feed conversion, where inclusion levels from 0.81% to 0.99% provide better performances. According to the equation of quadratic regression, the inclusion of 0.86% of valine provided greater weight gain. Regarding the hematological and biochemical parameters, there were differences among the treatments for hemoglobin, triglycerides, and cholesterol. Not difference was observed for the chemical composition and muscle fiber growth. It is recommended the inclusion of 0.86% of valine in the diet of juveniles of Nile tilapia because it provides greater weight gain.

Towards sustainable aquafeeds: Evaluating substitution of fishmeal with lipid-extracted microalgal co-product (Nannochloropsis oculata) in diets of juvenile Nile tilapia (Oreochromis niloticus).

Microalgae companies increasingly seek markets for defatted biomass that is left over after extracting omega-3 rich oil for human nutraceuticals and crude oil for fuels. Such a protein-rich co-product is a promising alternative to unsustainably sourced fishmeal in aquaculture diets. We report the first evaluation of co-product of the marine microalga Nannochloropsis oculata (N. oculata co-product) for replacing fishmeal in diets of Nile tilapia, a globally important aquaculture species. We conducted a nutrient digestibility experiment with N. oculata dried whole cells and N. oculata co-product, followed by an 84-day nutritional feeding experiment with N. oculata co-product. N. oculata co-product, more nutrient-dense than whole cells, had the highest digestibility for lysine, an essential amino acid that is often deficient in terrestrial crop meals; and for 20:5 n-3 EPA, making it a good option for EPA supplementation in tilapia feed. N. oculata co-product, despite containing higher amounts of protein than whole cells, had significantly lower digestibility for crude protein than whole cells. Apparent digestibility coefficients (ADC) of methionine were significantly lower in N. oculata co-product than in whole cells. The nutritional feeding experiment compared diets with N. oculata co-product that replaced fishmeal as follows: 0% replacement in reference diet (fishmeal as 7% of total diet) and test diets with 33%, 66% and 100% replacement of fishmeal (3%, 5.5%, and 8% of total diet, respectively). Results showed the 33% replacement diet yielded fish growth, feed conversion, and survival similar to the reference diet. Reduced digestibility and growth at greater N. oculata co-product inclusion levels may have been due to higher levels of anti-nutrients in co-product than whole cells. All diets yielded a n3:n6 ratio of tilapia fillet that is favorable for human consumption. Depositions of macro minerals and several trace elements in the fillet were not significantly different across diets. Thus, N. oculata co-product, when replacing 33% of fishmeal in tilapia feed, led to fish performance and flesh composition comparable to that of fish fed the reference diet, but its nutrient digestibility needs to be improved to achieve higher replacement levels.

Replacement of soybean meal by peanut meal in diets for juvenile Nile tilapia, Oreochromis niloticus

The use of alternative feeds aims to maintain productivity and reduce animal production costs. This objective of this study was to determine the nutritional value of peanut meal (PNM), as well as replacement of soybean meal (SBM) by PNM in diets for Nile tilapia, Oreochromis niloticus . To determine the apparent digestibility coefficients (ADC) of nutrients from the PNM, 40 fish (100 ± 4.3 g) were randomly distributed in four 250 L tanks and fed reference and test diets (50% PNM) plus 0.1% chromic oxide. Feces were collected by modified Guelph system. For the growth performance trial, 180 fish (13.4 ± 0.2 g) were randomly distributed in 30 200 L tanks and fed during 90 days with isoproteic (26.8% digestible protein) and isoenergetic (17.6 kJ g -1 digestible energy) diets containing replacement levels of 0, 25, 50, 75 and 100% of SBM digestible protein by PNM digestible protein. The experimental design was completely randomized with five treatments and six replicates. The ADC for protein from PNM was 90.9% whereas the ADCs for essential amino acids ranged from 88.7% for lysine to 97.6% for arginine. The feed conversion ratio was significantly affected when the SBM was totally replaced by PNM. The protein efficiency ratio, protein retention and whole-body protein content significantly decreased in fish fed diets containing PNM levels above 25% of PNM. Therefore, PNM can replace up to 25% of SBM without impairing juvenile Nile tilapia growth performance, feed efficiency, and body composition. Normal 0 21 false false false PT-BR X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabela normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi;}

Apparent digestibility of wheat and coproducts in extruded diets for the Nile tilapia, Oreochromis niloticus

SUMMARY In the present study, we investigated the digestibility of wheat and its coproducts in extruded diets for juvenile Nile tilapia. Specifically, we evaluated the apparent digestibility coefficients (ADCs) of dry matter (ADCDM), gross energy (ADCGE), crude protein (ADCCP), essential amino acids (EAAs), and non-essential amino acids (NEAAs) in winter wheat, spring wheat, wheat middling, wheat bran, and wheat germ in a diet fed Nile tilapia. A reference diet and test diets were used, with 5.0g/kg chromic oxide (Cr2O3) as the external indicator. The ADCDM, ADCCP, and ADCGE were higher (P&lt; 0.05) in winter wheat, spring wheat, and wheat germ than for wheat middling and wheat bran. The ADCs of all amino acids (AAs) were &gt;80%, except for threonine in wheat middling and wheat bran, exceeding 90% for winter wheat and wheat germ. The values of all investigated ingredients were high for ADCCP, and the ADCs of EAAs and NEAAs. A strong negative correlation was detected for crude fiber and ash with the ADCs of dry matter, gross energy, and crude protein. In general, wheat ingredients have good digestibility of protein and amino acids, but high fiber content reduces CDAMS and CDAEB in extruded diets for Nile tilapia.

Mixtures of oilseed meals as dietary protein sources in diets of juvenile Nile tilapia (Oreochromis niloticus l.)

The suitability of different mixtures of soybean meal (SBM), cottonseed meal (CSM) and groundnut cake (GNC) as ingredients to replace fish meal in the diets of Nile tilapia (Oreochromis niloticus L.), was evaluated over a 56-day growth period. Nine isonitrogenous (320g.kg -1 ), isolipidic (100 g.kg -1 ) and isoenergetic (18 KJ.g -1 ) test diets were formulated in which different mixture combinations of SBM, CSM and GNC proteins replaced fish meal (FM) protein at levels of 50% and 75%. The control diet had FM as the sole protein source. Fish were fed at 6 - 4% body weight per day. The growth experiment was conducted in plastic tanks in a recirculation system. Each dietary treatment was in triplicate. Growth performance and feed utilization of fish fed with the oilseed meal mixtures indicated that up to 50% replacement could be more effective than a single source for the substitution of fish meal in tilapia diets. This was particularly evident with the diet containing equal proportions of all oilseed meals (EQ50). Combination of oilseed meals in different proportions was more effective than the single individual sources. This could be due to a compensatory effect which led to some reduction of antinutritional factors coupled with improved essential amino acid profile in the diet as a result of mixing. Keywords : Oilseed meals, Nile tilapia, protein sources, mixtures, growth performance

Dietary Spirulina (Arthrospira platensis) replacement enhances performance of juvenile Nile tilapia (Oreochromis niloticus)

A feeding trial was conducted to evaluate the effects of Spirulina (Arthrospira platensis) inclusion in experimental diets of juvenile Nile tilapia (Oreochromis niloticus). Iso-nitrogenous and iso-lipidic diets were prepared using a positive control diet (S0) and four basal diets with A. platensis at 30 % (S30), 45 % (S45), 60 % (S60), and 75 % (S75) inclusion levels. Experimental diets were randomly assigned to tanks (13.35 kg m−3) with initial body weight of 0.89 ± 0.02 g in triplicates. The results of the feeding trial demonstrated significantly improved (P < 0.05) growth performance and hepatosomatic and viscerosomatic indices of fish fed S30. Blood chemical profile also indicated desirable values in fish fed A. platensis diets as compared to fish fed S0. On the contrary, fish fed S75 exhibited significantly reduced fish growth. Blood chemical analysis showed significant difference (P < 0.05) in levels of plasma triglyceride. Results of the present work indicate that 30 % A. platensis inclusion is deemed the optimal level of dietary replacement for increased growth performance, improved feed utilization efficiency, and enhanced overall health status of Nile tilapia juveniles.

Yeast extract on growth, nutrient utilization and haemato-immunological responses of Nile tilapia

Dietary supplementation (0, 10, 20, 40, 60, 80 g kg−1) of a nucleotide source (NuPro®) was evaluated on growth, nutrient utilization, haemato-immunological responses and resistance to experimental infection of Nile tilapia. Fish (2.63 ± 0.63 g) were fed experimental diets to satiation three times a day for 75 days. Feed intake increased linearly with increasing levels of NuPro® promoting higher weight gain (P < 0.05). Survival, feed conversion and protein retention were not affected. Following the growth trial, fish were challenged with Aeromonas hydrophila by intraperitoneal injection. Survival and innate immune responses (phagocytosis and lysozyme activity) were not significantly affected. However, among the haematological variables, thrombocyte, leucocyte and monocyte counts increased linearly (P < 0.05). The indirect measurement of digestibility in juvenile Nile tilapia (122.32 ± 11 g) indicated a linear decrease in protein (1.41%), dry matter (5.72%) and energy (4.10%) digestibility coefficients as dietary supplementation increased (P < 0.05). NuPro® showed to be a beneficial additive to be supplemented in diets for juvenile Nile tilapia, providing 32.8% increase in feed intake and 28.8% in weight gain, as well as in thrombocyte, leucocyte and monocyte counts in blood, possibly indicating a more efficient defence response in the highest dietary supplementation levels tested.

The sparing effect of cystine on methionine at a constant TSAA level in practical diets of juvenile Nile tilapiaOreochromis niloticus

The feeding experiment was conducted to evaluate the replacement effect of cystine on methionine at a constant total sulphur amino acid (TSAA) level in practical diets of juvenile Nile tilapia (Oreochromis niloticus). Soybean meal, cottonseed meal and rapeseed meal were used as the main protein sources in the diets containing 16.4 MJ kg−1 gross energy and 301 g kg−1 crude protein. Crystalline DL-methionine (Met) to L-cystine (Cys) were supplemented to fulfil various ratios of Met to Cys (60:40, 50:50, 40:60 and 30:70, based on an equimolar sulphur basis; and the analysed ratios were 53:47, 49:51, 34:66 and 31:69). Each diet was fed to triplicate groups of Nile tilapia juveniles (10.1 g mean initial weight) in a recirculation system for 8 weeks. The results showed that the growth performance and nutrient accretion were not affected by dietary methionine:cystine ratios (P > 0.05). However, the survival rates of fish tended to decrease with the decreasing methionine: cystine ratios. The only dietary treatment to achieve 100% survival was the 53:47 methionine: cystine treatment. And methionine digestibility decreased linearly with the decreasing methionine: cystine ratios (P < 0.05). Thus, it was concluded that cystine could replace up to approximately 47% of TSAA requirement on an equimolar sulphur basis without hampering growth performance in the practical diets of juvenile Nile tilapia.

Substituição parcial do farelo de soja pela farinha de carne e ossos em dietas para juvenis de tilápia-do-nilo

O objetivo deste trabalho foi avaliar os efeitos da substituição parcial do farelo de soja pela farinha de carne e ossos em dietas para juvenis de tilápia-do-nilo na digestibilidade, na saúde, no desempenho e no custo de arraçoamento. O experimento foi conduzido durante 14 semanas, com 400 juvenis (4,9±0,6 g) distribuídos ao acaso em 16 tanques. Os peixes foram alimentados com quatro dietas contendo 0, 15, 30 e 45% de substituição da proteína do farelo de soja pela proteína da farinha de carne e ossos. Foram avaliados parâmetros de desempenho, digestibilidade, hematologia e custo de arraçoamento. Os melhores resultados para ganho em peso e conversão alimentar aparente foram observados com 40 e 32% de substituição, respectivamente. O menor custo de arraçoamento foi obtido com 30 e 45%. Houve efeito linear decrescente dos coeficientes de digestibilidade aparente da proteína com o aumento nos níveis de farinha de carne e ossos. Os peixes alimentados com dietas contendo até 24% de substituição apresentam aumento da concentração de hemoglobina. A dieta com 32% de substituição da proteína do farelo de soja pela proteína da farinha de carne e ossos promove melhor conversão alimentar para tilápia-do-nilo.

Adição de lisina digestível em rações experimentais para juvenis de tilápia-do-nilo

Objetivou-se por meio deste estudo determinar a necessidade nutricional de lisina digestível em rações para juvenis de tilápia-do-nilo (Oreochromis niloticus). Setecentos e vinte peixes masculinizados (7,30±0,11g) foram alimentados durante 30 dias com oito rações (26,81% de proteína digestível e 3090kcal/kg de energia digestível da ração) contendo teores crescentes de lisina digestível (1,24; 1,36; 1,48; 1,60; 1,72; 1,84; 1,96 e 2,08%). As tilápias foram distribuídas em delineamento inteiramente ao acaso, com oito tratamentos, seis repetições e 15 peixes por unidade experimental. Foram avaliadas variáveis de desempenho (ganho de peso, taxa de crescimento específico, taxa de sobrevivência, consumo de ração, consumo de lisina digestível, conversão alimentar aparente, eficiência proteica para ganho, eficiência de lisina para ganho e eficiência de retenção de nitrogênio) e de composição corporal (teores de umidade, gordura, proteína, matéria mineral corporal e as taxas de deposição diária de proteína e gordura corporais). A elevação do teor de lisina digestível na ração não influenciou (P&gt;0,05) o consumo de ração, a taxa de sobrevivência e os teores de umidade e de matéria mineral corporal, mas melhorou de forma quadrática (P&lt;0,05) os demais parâmetros avaliados, com exceção do consumo de lisina e da eficiência de lisina para ganho, que aumentou e reduziu, respectivamente, de forma linear (P&lt;0,05). Recomenda-se que rações para juvenis de tilápia-do-nilo devam conter 1,84% de lisina digestível para máximo ganho de peso.

Protein: energy ratio in practical diets for Nile tilapia Oreochromis niloticus

The present study was conducted to evaluate the interaction of protein and energy ratio in low protein (20, 25 and 30 %) diets for juvenile Nile tilapia (Oreochromis niloticus) (initial weight 7.44 ± 0.03 g). Dietary protein to energy (P/E) ratio of nine practical diets ranged from 66.84 to 115.14 mg protein/kcal energy. Each diet was randomly assigned to four replicate groups of fifteen fish. After 10 weeks, Fish fed the lowest dietary protein (20 %) and lowest energy (2,600 kcal/kg) diets were significantly smaller than fish maintained on D5 (25/2800) and D6 (30/2800), However, there were no significant differences among all the treatments except D1. The whole body moisture and protein levels were significantly influenced by dietary protein and energy content. Whole body energy content and digestible energy retention were significantly influenced by energy content of the diet. Conversely, dietary protein level significantly influenced protein retention but it did not influence digestible energy retention. Under the reported conditions, the response of tilapia to dietary energy or protein was seen only at the lower levels of inclusion and tilapia demonstrated limited protein sparing as dietary energy was increased. However, this did modify the carcass composition through higher dietary energy.