Desempenho produtivo e crescimento muscular de linhagens de tilápia-do-nilo cultivadas na fase inicial
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Data
2011-02-23
Autores
Freitas, Thiago Mendes de [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O presente estudo teve como objetivo a comparação do desempenho produtivo e do crescimento muscular (morfometria das fibras musculares e expressão gênica dos fatores de regulação miogênica) de três linhagens de tilápia-do-nilo (GIFT, ―Supreme‖ e Tailandesa), alimentadas com dieta comercial contendo ou não o hormônio 17α-metiltestosterona, durante a fase inicial, quando ocorre o processo de diferenciação sexual. O trabalho foi conduzido em esquema fatorial (2 dietas X 3 linhagens), constituído por seis tratamentos com quatro repetições de cada, por 29 dias. As larvas (com quatro dias pós eclosão) foram estocadas na densidade de 4 larvas.L-1 e receberam dieta comercial farelada, em seis arraçoamentos diários. Foram realizadas cinco avaliações biométricas durante o experimento para verificação dos resultados de desempenho. Além disso, foram calculadas as taxas de sobrevivência, de masculinização e a homogeneidade dos animais no final do experimento. Para a avaliação morfométrica das fibras musculares (n = 8 indivíduos por tratamento) foram realizadas amostragens aos 4, 19 e 33 dias pós-eclosão, para confecção das lâminas de tecido muscular. Mensurou-se o diâmetro e a área de 200 fibras musculares para cada amostra, que foram distribuídas nas seguintes classes de diâmetro (D): classe 10 (D ≤10μm), classe 20 (10< D ≤20 μm), classe 30 (20< D ≤30 μm), classe 40 (30< D ≤40μm) e classe 50 (D > 40 μm). As análises de expressão gênica da MyoD e Miogenina foram realizadas por PCR em tempo real, com uma amostragem aos 4 dpe e outra aos 33 dpe. A linhagem ―Supreme‖ apresentou melhores respostas de desempenho produtivo e de sobrevivência, e menores valores do coeficiente de variação. As taxas de masculinização em todas as linhagens estiveram acima de 97%. A masculinização, por meio da adição de 17α-metiltestosterona, interferiu...
This study aimed to compare the performance and muscle growth (muscle fiber morphometry and gene expression of myogenic regulatory factors) from three Nile tilapia strains (GIFT, Supreme and Thai), fed commercial diet with or without the hormone 17α-methyltestosterone (MT) during the initial phase, when does the process of sexual differentiation. The experiment was conducted in a factorial scheme (3x2), making up six treatments with four replicates each. The larvae (4 days post-hatching, dph) were stocked at 4 larvae.L-1 and were fed a commercial diet six times a day, during 29 days. Fish growth was evaluated along the experiment, as well as the survival rates, masculinization rates and homogeneity of the animals at the end (29 days). For the morphometric analysis of the muscle fibers (n = 8 per treatment), samples were taken at 4, 19 and 33 days post-hatching (dph) and transversal sections of the epiaxial muscle were obtained. The diameter (d) and the area of 200 muscle fibers were measured in each sample, and the diameters were classified as follow: class 10 = d ≤ 10 μm, class 20 = 10 < d ≤ 20 μm, class 30 = 20 < d ≤ 30 μm, class 40 = 30 < d ≤ 40 μm, and class 50 = d > 40μm. The analysis of gene expression of MyoD and Myogenin were performed by real time PCR (sampling at 4 and 33 dph). The Supreme strain showed better growth performance, survival rates, and size homogeneity. All strains displayed masculinization rates above 97%. The use of MT affected the productive performance of Nile tilapia larvae, and the effects were different among the strains. The proportion of males and females of the juveniles that did not receive MT suggests a certain dependence on the strain used, requiring further studies in this direction. The ―Supreme‖ strain performed better, characterized by hyperplasia and hypertrophy of the muscle fibers... (Complete abstract click electronic access below)
This study aimed to compare the performance and muscle growth (muscle fiber morphometry and gene expression of myogenic regulatory factors) from three Nile tilapia strains (GIFT, Supreme and Thai), fed commercial diet with or without the hormone 17α-methyltestosterone (MT) during the initial phase, when does the process of sexual differentiation. The experiment was conducted in a factorial scheme (3x2), making up six treatments with four replicates each. The larvae (4 days post-hatching, dph) were stocked at 4 larvae.L-1 and were fed a commercial diet six times a day, during 29 days. Fish growth was evaluated along the experiment, as well as the survival rates, masculinization rates and homogeneity of the animals at the end (29 days). For the morphometric analysis of the muscle fibers (n = 8 per treatment), samples were taken at 4, 19 and 33 days post-hatching (dph) and transversal sections of the epiaxial muscle were obtained. The diameter (d) and the area of 200 muscle fibers were measured in each sample, and the diameters were classified as follow: class 10 = d ≤ 10 μm, class 20 = 10 < d ≤ 20 μm, class 30 = 20 < d ≤ 30 μm, class 40 = 30 < d ≤ 40 μm, and class 50 = d > 40μm. The analysis of gene expression of MyoD and Myogenin were performed by real time PCR (sampling at 4 and 33 dph). The Supreme strain showed better growth performance, survival rates, and size homogeneity. All strains displayed masculinization rates above 97%. The use of MT affected the productive performance of Nile tilapia larvae, and the effects were different among the strains. The proportion of males and females of the juveniles that did not receive MT suggests a certain dependence on the strain used, requiring further studies in this direction. The ―Supreme‖ strain performed better, characterized by hyperplasia and hypertrophy of the muscle fibers... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Tilapia (Peixe), Desempenho, Crescimento muscular, Oreochromis niloticus, Productive performance, Muscle growth
Como citar
FREITAS, Thiago Mendes de. Desempenho produtivo e crescimento muscular de linhagens de tilápia-do-nilo cultivadas na fase inicial. 2011. xv, 75 f. Dissertação (mestrado) - Universidade Estadual Paulista, Centro de Aquicultura, 2011.