Daniele Botaro

Aplicação do conceito de proteína ideal para redução dos níveis de proteína em dietas para tilápia-do-nilo (Oreochromis niloticus)

Este estudo foi realizado para se avaliar a reducao dos niveis de proteina em dietas para tilapia-do-nilo (5 a 125 g), adotando-se o conceito de proteina ideal. Cento e sessenta peixes (4,40 ± 0,9 g) foram distribuidos em um delineamento inteiramente casualizado, com quatro tratamentos [25,5; 27; 28,5 e 30% (controle) de proteina digestivel], tres repeticoes e dez animais por unidade experimental. Os aminoacidos sinteticos foram suplementados para se manter as proporcoes de aminoacidos de acordo com o conceito de proteina ideal. Os aminoacidos lisina, metionina e treonina foram suplementados para se obter os niveis de aminoacidos da dieta controle. As dietas foram fornecidas a vontade, durante 83 dias. Nao foram observados efeitos dos niveis de proteina sobre o ganho de peso, a conversao alimentar, o indice hepatossomatico, o peso da gordura visceral, a taxa de sobrevivencia, os niveis de proteina na carcaca e o diâmetro da fibra intermediaria. O aumento nos niveis de proteina resultou em reducao linear na taxa de eficiencia proteica e de retencao do nitrogenio e aumento linear na excrecao de nitrogenio. Foi observado efeito quadratico sobre o rendimento de carcaca e o teor de extrato etereo na carcaca; os melhores valores foram obtidos com 28,40 e 27,31% de proteina na dieta, respectivamente. Concluiu-se que e possivel a reducao do nivel de proteina de 30 para 27,5% em dietas para juvenis de tilapia do Nilo, sem efeitos negativos sobre o crescimento, rendimento de carcaca e a composicao quimica dos files. No entanto, a reducao do nivel de proteina de 30 para 25,5% acarreta reducao no diâmetro das fibras musculares vermelha e branca.

Redução da proteína da dieta com base no conceito de proteína ideal para tilápias-do-nilo (Oreochromis niloticus) criadas em tanques-rede

This study was carried out to evaluate the performance of Nile tilapia, cultured in net pens, and fed diets containing 27.0 (control), 25.2, 24.3, and 22.7% of digestible protein. Crystalline amino acids (L-lysine, DL-methionine and L-threonine) were added to keep amino acid levels according to the ideal protein profile and to simulate amino acid levels of the control diet. Fish (34.63±1.19 g) were hand-fed one of the four isoenergetic (3,075 kcal of digestible energy/kg, as fed basis) experimental diets until apparent satiation, three times a day during 90 days. A completely randomized design with four treatments, three replicates and 25 fishes per experimental unit was utilized. No effects of dietary digestible protein levels on weight gain, feed conversion, protein efficiency ratio, empty carcass weight, carcass yield, fillet weight and yield, survival, and hematocrit were observed. It was observed quadratic effect on feed intake and nitrogen excretion, wich increased up to 24.41 and 24.92% of dietary digestible protein, respectively. The reduction of digestible protein levels resulted in a linear increase of nitrogen retention. It was concluded that it is possible to reduce the dietary digestible protein from 27.0 (29.1% of CP) to 24.3% (26.6% of CP) in amino acid supplemented diets (based on ideal protein concept), for juvenile Nile tilapia, cultured in net pens, without adverse effects on growth performance, carcass yield and composition, hematological parameters and cost of diet/kg of fillet gain.

Organochlorine pesticides residues in feed and muscle of farmed Nile tilapia from Brazilian fish farms

Organochlorine pesticide (OCP) concentrations were determined in fish muscle and feed collected from four different fish farms in Brazil. Nile tilapia from two growth stages, juveniles and adults, collected at two intensive tanks farms (IT1 and IT2) and two net cage farms (NC1 and NC2), were analyzed by High Resolution Gas Chromatography/High Resolution Mass Spectrometry. Pesticides were detected in almost all samples, but no samples exceeded international maximum limits for safe fish consumption. ΣDDT was the predominant pesticide in fish muscle, found in all fish samples, and endosulfan was the most predominant pesticide in feed, found in all feed samples. No significant correlation (p>0.05) was observed between the different growth stages and OCP concentrations, although slightly higher OCP concentrations were observed in adults. Among the rearing systems, NC farmed fish presented higher lipid levels and, consequently, higher OCP concentrations than fish from IT farms. Some OCPs (ΣHCH, aldrin, dieldrin and endrin) presented strong positive correlations (p<0.05) between feed and fish muscle concentrations, while others (ΣDDT, mirex, chlordane, ΣHCB and endosulfan) presented no correlation. However, the low levels of the sum of contaminants found in most of the feed samples may explain the low contaminant levels in fish tissue.

Ácido linoléico conjugado (CLA) em dietas para tilápia-do-nilo: desempenho produtivo, composição química e perfil de ácidos graxos

The objective of this work was to evaluate the influence of the addition of CLA in the diet on Nile tilapia productive performance, chemical and fatty acids composition. Eighty reversed fish with 109 ± 10 g were used, distributed in eight tanks (0.8 m3 each) in density of ten fishes/tank, during 90 days. It was evaluated the inclusion in the diets of 2% of CLA (Luta-CLA®-BASF, Brazil) with 60% of isomers (cis-9,trans-11 and trans-10,cis-12) and 40% of vehicle (oleic acid and other fatty acids). As diets, a commercial extruded ration with 29% CP and 3000 kcal DE/kg of ration was used. At the end of the experiment all fishes were used for the evaluation of performance, of chemical composition and profile of fatty acids on liver and fillets. No differences for protein efficiency ratio, carcass yield, hepatosomatic index and visceral fat, were observed with the addition of CLA in the diet. The addition of CLA in the diet improved weight gain, feed intake and feed conversion ratio. Fishes fed diets with addition of CLA showed an increase in saturated fatty acids composition, reduction in n-6 fatty acids in the fillets and increase in n-3 fatty acids and total polyunsaturated fatty acids composition in the liver. There was an increase of protein in fillets of tilapia fed with rations enriched with CLA. CLA utilization improve productive performance, affect the fatty acids metabolism and pattern in fillets and liver and increase the body protein of Nile tilapia.

Mercury Levels in Feed and Muscle of Farmed Tilapia

BACKGROUND Fish consumption is considered the most important source of contaminant exposure for humans beings, and farmed fish can be exposed to contaminants via feed supply. METHODS Total mercury concentrations (THg) were determined in the muscle, liver, and feed of farmed Nile tilapia (juveniles and adults) from four different fish farms in Brazil (net cages and intensive tanks systems), by a flow injection mercury system. RESULTS Mercury concentrations observed in fish muscle were markedly lower (13.5-30.5 µg kg(-1)) than the values recommended by ANVISA/MAPA for edible part of fish (500 µg kg(-1)), and in the liver the concentrations found were higher than in the muscle. CONCLUSIONS These low levels of THg in farmed tilapia may be due to the low THg concentrations found in the analyzed fish feed, that ranged from 5.2 to 33.2 µg kg(-1), below the limit of 100 µg kg(-1) established by the European Commission.