Gill chemoreceptors and cardio-respiratory reflexes in the neotropical teleost pacu, Piaractus mesopotamicus

This study examined the location and distribution of O-2 chemoreceptors involved in cardio-respiratory responses to hypoxia in the neotropical teleost, the pacu (Piaractus mesopotamicus). Intact fish and fish experiencing progressive gill denervation by selective transection of cranial nerves IX and X were exposed to gradual hypoxia and submitted to intrabuccal and intravenous injections of NaCN while their heart rate, ventilation rate and ventilation amplitude were measured. The chemoreceptors producing reflex bradycardia were confined to, but distributed along all gill arches, and were sensitive to O-2 levels in the water and the blood. Ventilatory responses to all stimuli, though modified, continued following gill denervation, however, indicating the presence of internally and externally oriented receptors along all gill arches and either in the pseudobranch or at extra-branchial sites. Chemoreceptors located on the first pair of gill arches and innervated by the glossopharyngeal nerve appeared to attenuate the cardiac and respiratory responses to hypoxia. The data indicate that the location and distribution of cardio-respiratory O-2 receptors are not identical to those in tambaqui (Colossoma macropomum) despite their similar habitats and close phylogenetic lineage, although the differences between the two species could reduce to nothing more than the presence or absence of the pseudobranch.

Influence of the addition of antioxidants in vivo on the fatty acid composition of fish fillets

In this study, the influence of the addition of antioxidants in vivo on the fatty acid composition of the flesh of a freshwater fish known as pacu (Piaractus mesopotamicus) is verified. Four groups (one being the control group) of juvenile pacu were cultured on isocaloric and isoproteic diets. The lipid source was soybean oil and diets were added with either 100 ppm of alpha-tocopheryl acetate, or 100 ppm of BHT or 1.4 g of rosemary extract (Herbalox(R))/kg diet. The fatty acid composition of the lipids of the different groups was determined before and after irradiation at 2 and 3 kGy, respectively, for the evaluation of the protective effects of the different antioxidants. Similarly, thiobarbituric acid reactive substances (TBARS) were determined from irradiated and nonirradiated samples. The results showed that the use of antioxidants altered the fatty acid composition of the fillets. TEARS and irradiation confirmed their important role in protecting against lipid oxidation. Among all the antioxidants used, tocopherol was the most efficient, as shown by the highest percentage of polyunsaturated fatty acids (PUFA), by the lowest values of TEARS and by the analyses of the individual fatty acid levels at different irradiation doses. Significant statistical differences were observed only in 17% of the fatty acids in the fillets of the groups. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Growth and metabolism of pacu (Piaractus mesopotamicus Holmberg 1887) juveniles fed diets containing different protein, lipid and carbohydrate levels

To verify the potential of lipids and carbohydrates to spare dietary protein and to understand the intermediary metabolism of interaction of these nutrients in pacu juveniles, an experiment was carried out to evaluate pacu physiological and performance parameters. The experimental design was completely randomized with 12 treatments in a 2 x 2 x 3 factorial arrangement, consisting of diets containing two digestible protein levels (200 and 230 g kg(-1) PD), two lipid levels (40 and 80 g kg(-1)) and three carbohydrate levels (410, 460 and 500 g kg(-1)). Fish-fed 230 g kg(-1) digestable protein (DP) showed increased glycaemia, decreased hepatic glycogen, as well as a smaller intake index and better feed conversion ratio. The higher dietary lipid level (80 g kg(-1)) reduced protein intake and serum protein concentration, increased liver and body fat content, but did not affect growth. At a lipid level of 80 g kg(-1), the increase in dietary carbohydrate levels promoted greater weight gain (WG), crude protein intake (CPI) and better feed conversion ratio (FCR). For fish fed diets containing 40 g kg(-1) lipid, the best energy-productive values (EPV) were obtained at 460 g kg(-1) carbohydrate. Increased levels of the main nutrients in the diets reduced the levels of serum triglycerides, while the increase in energy concentration increased the hepatosomatic (HSI) and glycaemia index values. Pacu used lipids as effectively as carbohydrates in the maximization of protein usage, as long as dietary protein was at a level of 230 g kg(-1) DP. The physiological parameters indicated that the best balance between the DP, dietary lipid and carbohydrate levels within the ranged this trial was obtained at 230, 40 and 460 g kg(-1), respectively, without lower growth.

Growth and survival of pacu Piaractus mesopotamicus (Holmberg, 1887) juveniles reared in ponds or at different initial larviculture periods indoors

Five-day-old pacu larvae (Piaractus mesopotamicus) with average length and weight of 5.96 mm and 0.42 mg, respectively, were reared as follows: in a semi-intensive system with larvae stocked directly into fertilized ponds (IL0)-and an initial intensive larviculture system with larvae maintained in a laboratory for 3 (IL3), 6 (IL6) and 9 (IL9) days, before being transferred to fertilized ponds. During the indoor phase, larvae were fed Artemia nauplii. Intensive-culture survivals were high (95.6%, 86.4% and 83.8% for IL3, IL6 and IL9, respectively) and at the end of the 45-day period, the longer the larvae were kept in the intensive system, the better the juvenile survival in the ponds. IL9 and IL6 survival rates were 54.0% and 45.4%, respectively, significantly higher (P < 0.05) than IL0 (11%) and IL3 presented an intermediate rate (25.3%). Due to the low survival rate of IL0, length and weight were higher (P < 0.05) when compared to IL6 and IL9; and the differences between their survival rates affected size distribution of juveniles among treatments. Treatments, which resulted in high survival (IL6 and IL9), presented a great number of small fish. In contrast, IL0 and IL3 produced many large and extra large individuals. In general, the results indicate that pacu juvenile production by initial intensive larviculture (IL6 and IL9) was the most efficient method. Therefore, further studies should be conducted in order to improve larval growth in the laboratory and handling techniques in both the laboratory and ponds. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Apparent digestibility of protein, energy, and amino acids in some selected feed ingredients for pacu Piaractus mesopotamicus

The apparent digestibility coefficients (ADCs) of amino acids (AA), protein, and energy in six feed ingredients (Brazilian fish meal, soybean meal, corn gluten meal, alcoholic yeast, corn, and wheat bran) we evaluated for pacu juveniles. In general, all ingredients showed high digestibility values for all AA, and differences among ADCs of individual amino acid were detected (P < 0.01). Corn gluten, soybean, and fish meals had the highest ADCs of AA. The ADCs of protein in fish meal, yeast, and corn gluten meal should not be used as AA digestibility indicators, because those showed differences up to 6.7% between the ADCs of protein and AA. All ingredients had lower ADCs of energy than corn gluten meal (P < 0.01). Lysine was the first limiting amino acid in fish meal, corn gluten meal, wheat bran, and corn, and the second limiting amino acid in soybean meal, as methionine was the first limiting amino acid in soybean meal and yeast. However, the soybean meal was the best quality protein source, as it had the highest digestible essential amino acid index. This demonstrated that digestible amino acid values can be used to formulate practical diets for pacu, preventing potential deficiencies or excess that might cause environmental and economic losses.

Dietary digestible lysine requirement and essential amino acid to lysine ratio for pacu Piaractus mesopotamicus

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

Effects of processing on physical characteristics of diets with distinct levels of carbohydrates and lipids: the outcomes on the growth of pacu (Piaractus mesopotamicus)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Salga seca e úmida de filés de pacu (piaractus mesopotamicus)

The goal of this study was to evaluate the process of salting and dry salting of fillets in pacu (P. mesopotamicus), from cultivation in cages. Fillet with skin were salted at a rate of 40% of salt in relation of the initial weight, for a period of 10 days. After processing, were evaluated for microbiological and centesimal composition of fillets subjected to salting and determining the concentration of sodium chloride (NaCl) and calculation of income. The centesimal composition were evaluated the protein, ether extract, moisture and ash of the raw material fresh and processed products by salting. The microbiological analysis included the determination of coliforms at 45 degrees C, Salmonella and Staphylococcus coagulase positive. The pacus subjected to umided and dry salting were within quality control standards established by the legislation. The content of umided, protein, lipids and chlorides showed differences (p< 0.05) between the processes of salt. However both forms can be used for the development of technological processes of low investment by encouraging new options for fish consumption.

The effect of ions and adenosine nucleotides on the activity of lactate dehydrogenase from the epaxial muscle of fish

Lactate dehydrogenase was partially purified from the epaxial muscle of Piaractus mesopotamicus (pacu) and its hybrid Piaractus mesopotamicus x Colossoma macropomus (tambacu). This preparation was used for kinetic studies carried out at pH 6.0 and 7.5. It was also used for the study of the inhibition properties of adenosine nucleotides = ATP, ADP, AMP =, divalent ions Ni2+, Cu2+, Co2+ and the anions oxamate and oxalate.

Acid and fermented silage characterization and determination of apparent digestibility coefficient of crude protein for pacu Piaractus mesopotamicus

Three types of raw materials including commercial waste from saltwater (SW), freshwater fish (FW) and tilapia fillet residue (FR) were used to produce fish silage by either acid digestion (2% formic acid and 2% sulfuric acid) or anaerobic fermentation (5% of Lactobacillus plantarum and 15% sugar cane molasses). Six test diets were used in digestibility trials prepared with 70% reference diet and 30% of each experimental silage. These diets were fed to juvenile pacu Piaractus mesopotamicus (146 g average weight) in triplicate. Fish were kept in 500-L tanks and feces collected by manual extrusion. It was observed for both processes that SW waste always had the highest moisture content and lowest fat and ash. Highest crude protein levels were found in silages from commercial fish waste (SW and FW) made from whole fish unfit for human consumption. However, apparent digestibility coefficients did not vary among diets (P > 0.05). Although values did not differ statistically, fermented silage consistently displayed higher digestibility coefficients compared to acid silage. The silages exhibited relatively high protein digestibility (72.5-80.0%), thus suggesting the feasibility of using fish industry by-products in aquaculture feeds.

Composição corporal e índices biométricos do pacu, Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes, Characidae) submetido a ciclos alternados de restrição alimentar e realimentação

The present paper evaluated, through hepatosomatic/mesenteric fat indexes and body composition, the pacu energy utilization when submitted to alternated food restriction/refeeding cycles during the growout period. Juveniles were distributed in three pounds and submitted to different feeding programs: A (ad libitum daily feeding), B (4-week feeding restriction and 9-week refeeding) and C (6-week feeding restrictions and 7-week refeeding), totaling 13 weeks for each cycle (4 experimental cycles). At the end of the periods, fish were sampled to obtain biometrics and biochemical data. The results showed that, during the first two cycles, C treatment obtained the best compensatory growth. Carcass lipid and water contents were inversely related, with body fat decrease. Fishes under B and C treatment during food restriction utilized liver and mesentery energy stores. These parameters were re-established in the refeeding phase, in all cycles.

Alterações hematológicas e histopatológicas em pacu, Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes, Characidae), tratado com sulfato de cobre (CuSo4)

This paper evaluated the haematological and glycaemic parameters in Piaractus mesopotamicus (Osteichthyes, Characidae) infected with Monogenea Anacanthorus penilabiatus Boeger, Husak & Martins, 1995 (Dactylogyridae) after treatment with 0.50 mg/L and 1.00 mg/L of copper sulphate (CuSO4). The efficacy of the CuSO4 was observed in the first day after administration but not after eight, fifteen or thirty days. The histopathological analyses showed hyperplasia of the epithelium and circulatory changes in the gills. In the first day after treatment significant changes (P<0.05) in the total count of erythrocyte, leucocyte, mean corpuscular haemoglobin concentration (MCHC) were observed. The fishes treated with 0.50 mg/L showed decrease in the haemoglobin levels and in the percentage of neutrophils (P<0.05). The dose of 1.00 mg/L provoked increase of glycaemia but reduction in the lymphocytes percentage when compared with 0.50 mg/L in the 8th day. Fifteen days after 1.00 mg/L treatment, values of mean corpuscular volume (MCV) and special granulocitic cells (S.G.C.) percentage decreased. Nevertheless, increase of total leucocyte number was observed. Thirty days after treatment with 0.50 mg/L showed increased S.G.C. and treatment with 1.00 mg/L showed increased lymphocyte.

Apparent digestible energy and nutrient digestibility coefficients of diet ingredients for pacu Piaractus brachypomus

The digestible energy and apparent nutrient digestibility coefficients of common diet ingredients were determined for pacu Piaractus brachypomus (370.21 ± 17.56 g). Fish were fed with pelleted practical diets to apparent satiation and the feces were collected by siphoning. The digestibility value for each ingredient was determined by comparison of the digestibility of a test diet with a reference diet (24.5% crude protein and 1% chromic oxide). The digestible energy values of soybean meal (SBM), fish meal (FM), corn (CN), and wheat bran (WB) were 2382, 3826, 3353, and 1784 kcal/kg, respectively. The apparent dry matter digestibility coefficients were 83.72, 90.14, 89.13, and 82.05% for SBM, FM, CN, and WB, respectively. The apparent crude protein digestibility coefficients were 75.88, 90.49, 85.06, and 61.62% for SBM, FM, CN, and WB, respectively. The apparent lipid digestibility coefficients were 63.03, 77.00, 83.01, and 82.45% for SBM, FM, CN, and WB, respectively. The digestibility of protein, lipid, and energy from SBM were somewhat low compared to values for other warmwater omnivorous fishes, but similar to values reported for pacu-caranha P. mesopotamicus. Otherwise, the nutrient and energy availability of the ingredients to P. brachypomus was similar to that of other fish. This information will be useful in formulating nutritious, economical diets for pacus. © by the World Aquaculture Society 2004.

Effect of dietary supplementation with vitamin E and stocking density on macrophage recruitment and giant cell formation in the teleost fish, Piaractus mesopotamicus

The effect of dietary supplementation with 0, 100 and 450 mg of vitamin E (DL-α tocopheryl acetate)/kg of a dry diet on the kinetics of macrophage recruitment and giant cell formation in the pacu, maintained at different stocking densities (5 kg/m3 and 20 kg/m3), was investigated by insertion of round glass coverslips into the subcutaneous connective tissue. After a feeding period of 18 weeks, the coverslips were implanted and later removed for examination at 2, 7 and 15 days post-implantation. Fish fed diets supplemented with 450 mg of vitamin E showed an increase (P<0.05) in the accumulation of macrophages, foreign body giant cells and Langhans type cells. The kinetics of macrophage recruitment and giant cell formation on the glass coverslips appeared to be strongly influenced by vitamin E supplementation, since fish fed a basal diet and held at high stocking densities showed low numbers of adhering cells on the coverslips, and high concentrations of plasma corticosteroids. On the other hand, fish given a diet supplemented with 450 mg of vitamin E did not show a similar difference in plasma cortisol concentrations related to stocking density. The effect of cortisol concentrations on carbohydrate metabolism, analysed by assessment of plasma glycaemia, was not clear. Blood glucose concentrations did not vary substantially with the different treatments examined. These results suggest that vitamin E may contribute to the efficiency of the fish's inflammatory response by increasing macrophage recruitment and giant cell formation in the foreign body granulomatous reaction. Vitamin E appeared to act on the stress response of pacus by preventing a stress-related immunosuppression. © 2005 Elsevier Ltd. All rights reserved.

Digestibilidade e tempo de trânsito gastrintestinal de dietas contendo níveis crescentes de fibra bruta para pacu

This work aimed to evaluate the effect of increasing dietary fiber levels on the digestibility and gastrointestinal transit time (GTT) for pacu. The digestibility trial used 288 pacu in a completely randomized design, fed in aquaria and transferred to a modified Guelf-type feces collector, using the partial sampling method. The inert marker on the diets was chromic oxide (1%) to establish the diet digestibility. In the GTT assay, 288 pacu were distributed in 24 aquaria in a completely randomized design. Fish were fed with two colored diets - green and white - and feces color was determined after abdominal pressure. The white and green diets used 1% of titanium and chromic oxides, respectively. Total GTT was determined when all fish showed green feces. The apparent digestibility coefficients and GTT of diets decreased as dietary fiber levels increased. These results indicated that 9% dietary fiber can be used in pacu diets without negative effects on energy, protein, crude fiber and ether extract digestibility and GTT.