Nucleotides, β-glucans, ascorbic acid, α-tocoferol, and different concentrations of a vitamin-mineral premix promote growth of Nile tilapia juveniles

ABSTRACT Feed additives, such as β-glucans, nucleotides, ascorbic acid (vitamin C), and α-tocopherol (vitamin E) can improve fish immunity and contribute to enhanced zootechnical performance of the fish. This study aimed to evaluate the effect of different concentrations of vitamin- mineral premix with or without the inclusion of an immunostimulant boost (β-glucans, nucleotides and vitamins C and E) on the zootechnical performance, hemato-immunological parameters, histological changes, and survival of Nile tilapia juveniles. To this end, isocaloric and isoproteic diets were prepared with three different concentrations of vitamin-mineral premix (1.0, 1.5, and 2.0 kg ton-1); additionally, the effects of 4% immunostimulant boost in the diet were examined considering six diets (without the immunostimulant boost: 0.1%, 0.15%, and 0.2%, and with the immunostimulant boost: 0.1% I, 0.15% I, and 0.2% I). We used 24 experimental units, each including 15 fish. Nile tilapia juveniles (1.88 g±0.25) were fed for 50 d with supplemented diets. Further, zootechnical indexes; histological changes in the liver, spleen, and intestine; intestinal morphology; and hemato-immunological parameters were evaluated. The fish that received supplementation showed higher zootechnical values, compared to those that did not receive the supplementation of immunostimulant reinforcement. Weight gain (30.45g±3.06), daily weight gain (0.60g±0.06), final weight (32.41g±3.15) and feed conversion (0.95±0.06) were higher in tilapia fed with an inclusion concentration of 0.2%. Hematological parameters were not affected by either the pre-mix concentrations or the booster of the immunostimulant. There was an increase in the number of intestinal folds, length of the fold, total area and number of goblet cells in the group supplemented with immunostimulant reinforcement. Supplementation with the immunostimulant promoted growth and improved intestinal morphology and immunological parameters of Nile tilapia juveniles

Períodos de condicionamento alimentar de juvenis de pirarucu na transição da alimentação de ração úmida para seca

Resumo: O objetivo deste trabalho foi avaliar o efeito de períodos de condicionamento alimentar sobre o desempenho produtivo e a sobrevivência de juvenis de pirarucu (Arapaima gigas), durante a transição da alimentação com massa de peixe moída para dieta formulada seca. Animais com 15,8±1,2 g foram avaliados com substituições graduais da dieta a cada 2, 3, 4 e 5 dias. Após 12 dias de condicionamento alimentar, as substituições a cada dois e três dias proporcionaram as maiores taxas de crescimento específico. Recomenda-se a substituição da dieta à base de peixe moído por dieta formulada seca a cada dois ou três dias

Vegetable oil sources in diets for freshwater angelfish (Pterophyllum scalare, Cichlidae): growth and thermal tolerance

The influence of fatty acid composition of the diets on the productive performance and on cold and heat tolerance of juvenile freshwater angelfish (Pterophyllum scalare), in three different phases, was studied. Phase I studied the productive performance of freshwater angelfish in a completely randomized experimental design with four treatments, canola, linseed, olive and soybean oils and four replicates during 50 days using 192 fish in 16 aquaria. Phase II studied the cold tolerance of juvenile freshwater angelfish using 72 juvenile freshwater angelfish, coming from phase I and maintained in 12 aquaria climatized chamber. The temperature was reduced 1ºC per day, until the observation of 100% fish mortality. Phase III, it was studied the heat tolerance of juvenile freshwater angelfish employing an identical procedure to phase II, but with a daily increase of 1ºC. Significant differences (P>0.05) were not observed for any parameters evaluated. Thus, it was concluded that the type of vegetable oil (canola, linseed, olive and soybean) used as a diet supplement did not affect the productive performance, nor the tolerance to cold and heat, of juvenile freshwater angelfish