Characterization and evaluation of the impact of feed management on the effluents of Nile tilapia (Oreochromis niloticus) culture

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Hematology and productive performance of nile tilapia (Oreochromis niloticus) naturally infected with Flavobacterium columnare

Columnaris disease is one of the main causes of mortality in tilapia rearing and is responsible for large economic losses worldwide. Hematology is a tool that makes it possible to study organisms' physiological responses to pathogens. It may assist in making diagnoses and prognoses on diseases in fish populations. The hematological variables of nile tilapia were studied in specimens with a clinical diagnosis of columnaris disease and in specimens that were disease-free. The total erythrocyte count, hemoglobin rate, hematocrit percentage, mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), organic defense blood cell percentages (leukocytes and thrombocytes) and hepatosomatic and splenosomatic index were determined. The results showed that there were changes in the erythrocytic series and in organic defense blood cells, in the fish infected with the bacterium, with reductions in erythrocytic variables and significant increases in the numbers of circulating lymphocytes and neutrophils.

Eutrophization process in a system used for rearing the nile tilapia (Oreochromis niloticus), São Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The effect of increased light intensity on the aggressive behavior of the Nile tilapia, Oreochromis niloticus (Teleostei: Cichlidae)

Animals show behavioral and physiological changes that emerge in response to environmental perturbations (i.e., emergency life-history stages). In this study, we investigate the effects of light intensity on aggressive encounters and social stability in groups of adult male Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The study compared the behavior observed under low (280.75 ± 50.60 lx) and high (1394.14 ± 520.32 lx) light intensities, with 12 replicates for each treatment. Adult fish were isolated in 36-L aquaria for 96 hours, and three males were grouped for 11 days in 140-L aquaria. Agonistic behavior was video-recorded (10 min/day) on the 3rd, 5th, 7th, and 9th day to quantify aggressive interactions and social stability. There was an effect of light intensity and day of observation on the total number of agonistic behaviors performed by the fish group. Besides, increased frequency of aggressive interactions (the sum of the four sessions) by the alpha, beta and gamma fish occurred at the higher light intensity. The dominance ranks of the fish remained unchanged across the observation sessions under both the low and high light intensities. We concluded that enhanced light intensity has a cumulative effect that increases the aggressiveness of the Nile tilapia but that this effect is not sufficiently strong to destabilize the social hierarchy.

Inflammatory responses of Nile tilapia Oreochromis niloticus to Streptococcus agalactiae: effects of vaccination and yeast diet supplement

This study evaluated the effects of dietary supplementation with 0.3% Saccharomyces cerevisiae yeast cell wall and of vaccination against Streptococcus agalactiae on the cellular component of acute inflammation induced in the coelomic cavity of Nile tilapia Oreochromis niloticus and on survival of the fish after challenge. A total of 84 tilapia of mean (+/- SD) weight 125.0 +/- 1.5 g were distributed among twelve 310 l fiberglass tanks according to a 2 x 2 x 3 factorial design in the following manner: with and without supplementation; 2 stimulations (oily solution without S. agalactiae vaccine and vaccination); 15 d later all fish were intracoelomically challenged with 10(8) CFU ml(-1) of a homologous strain of S. agalactiae, and evaluated after 6, 24 and 48 h, with 7 replicates. The fish received the non-supplemented or supplemented diet for a total of 77 d. The vaccination was performed on the 60th day, intracoelomically, as a single injection of 0.5 ml of the vaccine containing 10(8) CFU ml(-1). Fifteen days later, all the fish were challenged with S. agalactiae by means of an intracoelomic inoculation of 10(8) CFU ml(-1). No mortality was observed among the supplemented fish. The fish that were fed the non-supplemented diet and immunized with the bacterium presented a mortality rate of 28.5%. Among the non-supplemented and non-immunized fish, the mortality rate was 38.09%. Supplementation, in both vaccinated and non-vaccinated fish, induced larger accumulations of thrombocytes, lymphocytes and macrophages at the inflammatory focus. The results suggest that supplementation with 0.3% yeast cell wall, in both vaccinated and non-vaccinated fish, improved the inflammatory response of the fish and protected against the challenge. Vaccination increased the defense response, but the effect was stronger when associated with supplementation with S. cerevisiae.

Muscle delta C-13 change in nile tilapia (Oreochromis niloticus) fingerlings fed lants grain-based diets

The effects of grain-based diets from C3 or C4-cycle plants on muscle delta C-13 change process in Nile tilapia (Oreochromis niloticus) fingerlings were investigated. Two groups of sex reversal males Nile tilapia fingerlings were fed with isoproteic (32.0% DP) and isocaloric (3200 kcal DE/kg) diets, differing from each other by their delta C-13. Muscle samples were collected and the carbon isotopic composition was measured. For C4 diet, the formula for the muscle delta C-13 change related to the intake time of a new diet was delta C-13=- 14.88 - 9.2 1 e(-0.0209t) and the half-life (T) of the muscle carbon was 33.2 days. For C3 diet, the formula was delta C-13 = - 25.43 + 8.59e(-0.0533), with T = 13 days. The C3 diet was considered more appropriate based on its palatability and consequent larger food intake than the C4 diet, resulting in an increased muscle delta C-13 change rate. However, for future studies, would be necessary to mix both the C3 and C4 feedstuffs to formulate diets nutritionally appropriated, with contrasting stable isotopes signatures. Tissue delta C-13 change rate is therefore indicated as a promising tool to better understand the biotic and abiotic factors that influence nutrients utilization from the diet and animal growth. (c) 2006 Elsevier B.V. All rights reserved.

Muscle delta C-13 change in Nile tilapia (Oreochromis niloticus): Effects of growth and carbon turnover

The contribution of growth and turnover to the muscle delta C-13 change process was investigated using mathematical models which associate delta C-13 change to time of intake of a new diet or increase in body mass. Two groups of Nile tilapia (Oreochromis niloticus) were fed on diets based on C3 (sigma C-13 = - 25.64 +/- 0.06 parts per thousand) or C4 (delta C-13= -16.01 +/- 0.06 parts per thousand) photosynthetic cycle plants to standardize the muscle delta C-13. After establishing the carbon isotopic equilibrium, fish (mean mass 24.12 +/- 6.79 g) then received the other treatment diet until a new carbon isotopic equilibrium could be established, characterizing T1 (C3-C4) and T2 (C4-C3) treatments. No significant differences were observed in fish productive performance. Good fits were obtained for the models that associated the delta C-13 change to time, resulting in carbon half-life values of 23.33 days for T1 and 25.96 days for T2. Based on values found for the muscle delta C-13 change rate from growth (0.0263 day(-1) and 0.0254 day(-1)) and turnover (0.0034 day(-1) and 0.0013 day(-1)), our results indicate that most of the delta C-13 change could be attributed to growth. The application of model that associated the delta C-13 change to body mass increase seems to produce results with no apparent biological explanation. The delta C-13 change rate could directly reflect the daily ration and growth rate, and consequently the isotopic change rates of carbon and other tissue elements can be properly used to assess different factors that may interfere in nutrient utilization and growth. (c) 2006 Published by Elsevier B.V.

Haematological response and growth performance of Nile tilapia (Oreochromis niloticus L.) fed diets containing folic acid

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Amino acid availability and protein digestibility of several protein sources for Nile tilapia, Oreochromis niloticus

Apparent amino acid availability coefficients and protein digestibility of four animal products [fish meal (FM), meat and bone meal (MBM), poultry by-product and feather meal] and four plant protein-rich products [soybean meal (SBM), cottonseed meal-28, cottonseed meal-38 and corn gluten meal (CGM)] were determined for Nile tilapia, Oreochromis niloticus. Ingredients were incorporated to a practical reference diet at a 7 : 3 ratio (70% of reference diet and 30% of test ingredient). Chromic oxide was used as external digestibility marker. Among animal products poultry by-product meal (PBM; 89.7%) and FM (88.6%) presented the highest apparent protein digestibility (APD) while MBM (78.4%) and feather meal (78.5%) presented the lowest APD. Among plant protein-rich products CGM (91.4%) and SBM (92.4%) presented the highest APD values while cottonseed meal-28 presented the lowest APD (78.6%). Average apparent amino acid availability of feed ingredients was similar to protein digestibility with 92.3%, 89.6%, 73.4%, 80.7%, 88.9%, 84.4%, 91.2% and 79.7% values for SBM, CGM, cottonseed meal-28 and 38, FM, MBM, PBM and feather meal respectively. These results indicate that O. niloticus is able to utilize efficiently different feedstuffs.

Productive performance of Nile tilapia (Oreochromis niloticus) fed at different frequencies and periods with automatic dispenser

Avaliou-se o desempenho de tilápias-do-nilo (Oreochromis niloticus) produzidas em tanque-rede, providas de dispensadores automáticos de ração, alimentadas em diferentes frequências - uma vez por hora e a cada duas horas - e períodos - durante o dia, à noite ou ambos. Dezoito tanques-rede de 1.0m³ foram colocados em um tanque de 2000m² com dois metros de profundidade e renovação de água de 5%. Cento e setenta tilápias, com peso inicial de 16.0±4.9g foram distribuídas em cada tanque-rede de 1m³ e a taxa alimentar foi ajustada a cada 21 dias junto com as biometrias. As medidas foram coletadas de março a julho (outono e inverno). Observou-se diferença significativa para peso final (P<0.05) entre os tratamentos. O aumento da frequência alimentar melhorou o desempenho produtivo de tilápias-do-nilo produzidas em tanque-rede e permitiu melhor manejo alimentar. A melhor conversão alimentar para alta frequência, 24 vezes dia-1, pode resultar em uma economia de até 360kg de ração por tonelada de peixe produzido, melhorando a sustentabilidade econômica para produção de tilápia e sugerindo menor poluição ambiental.

MyoD, myogenin and proliferating cell nuclear antigen expression in growing Nile tilapia (Oreochromis niloticus L.)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Growth performance of Nile tilapia, Oreochromis niloticus, fed diets containing levels of pyridoxine and haematological response under heat stress

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aggressive behaviour traits predict physiological stress responses in Nile tilapia (Oreochromis niloticus)

This study tested whether aggressive behaviour can predict individual variation in stress responses of Nile tilapia Oreochromis niloticus. We used a mirror test to measure tendency to aggressive behaviour, and calculated the attack frequency and time until the first attack (latency) for each fish. One day later, we measured plasma cortisol and glucose, and two days later, we measured ventilatory frequency (VF) (pre-confinement responses). Immediately after the VF measure, we subjected the same fish to 30 min confinement, followed by measurements of cortisol, glucose, and VF (post-confinement responses). We found that post-confinement stress cortisol, glucose, and VF were higher than pre-confinement responses. Attack frequency was negatively correlated with VF and latency was positively correlated with baseline glucose and VF. Thus, we conclude that attack frequency and latency to a mirror reflection could be used to predict baseline levels of physiological stress indicators in Nile tilapia.

Hierarchical status and colour preference in Nile tilapia (Oreochromis niloticus)

We studied the colour preference of isolated Nile tilapia (Oreochromis niloticus) and whether previous residence or body size can affect environmental colour choice. In the first phase, a cylindrical tank was divided into five differently coloured compartments (yellow, blue, green, white and red), a single fish was introduced into the tank and the frequency at which this fish visited each compartment was recorded over a 2-day study period. An increasingly larger fish (approx +2 cm in length each time) was then added into the tank on each of days 3, 5 and 7 (=four fish in the tank by day 7), and the frequency at which each fish visited the different compartments of the tank was observed twice a day to obtain visit frequency data on the differently sized fishes. This experiment was replicated six times. In the first phase, the solitary fish established residence inside the yellow compartment on the first and second days. Following the introduction of a larger fish, the smaller fish was displaced from the occupied compartment. Nile tilapia possibly shows this preference for yellow as a function of its visual spectral sensitivity and/or the spectral characteristics of its natural environment. Moreover, body size is an important factor in determining hierarchical dominance and territorial defence, and dominant fish chose the preferred environmental colour compartment as their territory.

Muscle growth in Nile tilapia (Oreochromis niloticus): histochemical, ultrastructural and morphometric study

Muscle growth in Nile tilapia (Oreochromis niloticus) was studied focusing on histochemical, ultrastructural, and morphometric characteristics of muscle fibers. Based on body length (cm), we studied four groups: G1 = 1.36+/-0.09, G2 = 3.38+/-0.44, G3 = 8.90+/-1.47, and G4 = 28.30+/-3.29 (mean+/-S.D.). All groups showed intense reaction to NADH-TR in subdermal fibers and weak or no reaction in deep layer fibers. In G3 and G4, an intermediate layer was also observed with fibers presenting weak reaction; in G4, groups of fibers with intense reaction were observed in the subdermal region. The myosin ATPase (m-ATPase) activities were acid-stable and alkali-labile in subdermal fibers; most deep layer fibers were alkali-stable and acid-labile. Intermediate fibers were acid-labile and alkali-stable. Two fiber populations were observed near deep muscle layer: one large presenting weak acid- and alkali-stable and the other small alkali-stable.During growth, muscle fiber hypertrophy was more evident in intermediate and white fibers for G3 and G4. However, in these groups, the presence of fiber diameters less than or equal to21 mum suggested that there is still substantial fiber recruitment, confirmed by ultrastructural study, but hypertrophy is the main mechanism contributing to increase in muscular mass. (C) 2003 Elsevier B.V. Ltd. All rights reserved.