Avaliação genética do crescimento de Tilápia do Nilo

• Ano de defesa: 2007
• Autor(a) principal: Silva, Rodrigo Fortes da
• Orientador(a): Torres, Robledo de Almeida
• Banca de defesa: Carneiro, Antônio Policarpo Souza , Lanna, Eduardo Arruda Teixeira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Parâmetros genéticos; Tilápia do Nilo
• Palavras-chave em Inglês: Genetic parameters; Nile Tilapia
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS
• Link de acesso: http://locus.ufv.br/handle/123456789/5855

Two hundred dams and two hundred sires of Nile Tilapia (Oreochromis niloticus) were captured using fish-net in an earthen tank from a farm in the country area of Viçosa. First the animals were put into five water tanks of 5000 liters keeping the same animal density between the water tanks. After 30 days, 20 couples were selected accordingly with health status and reproductive performance potential. They were distributed between 20 water tanks of 1000 liters, each couple for each water tank. After this fish couples started their reproduction. After spawning, offsprings stayed in the same tanks until 60 days old, when they were transferred to larger tanks. Animals were identified during the first measurement on day 60th. One technique was developed to identify the fishes, using letters followed by number. After those procedures, data collection started with the recording of body weight and total length during the whole experiment. A culling rate was determined for each phase of measurement, to adequate the animal density in the tanks. At the end of the experiment animals were slaughtered and ungutted carcass weight and dressing percentage were recorded. The Proc Mixed was used to evaluate the variance and covariance components to obtain the heritabilities and correlations. It was applied the unicharacteristic model via REML (Restricted Maximum Likelihood), using the statistic program SAS. The genetic correlation between the characteristics was obtained using SAS too, and was estimated using components of covariance of matting. The heritabilities were high, for weight varied between 0.91 and 1.36 for 150 and 60 days respectively and for total body length the heritabilities were of 0.94 and 0.95 also for 60 and 150 days old. For daily weight gain heritability was 0.87 and for daily length gain was 0.60, both results were considered high. This demonstrates that individual selection can be applied to these characteristics. On the sixth month of age all animals were slaughtered to obtain ungutted carcass weight and dressing percentage. Heritability values for these characteristics were 1.00 and 0.21 respectively. The high values of Nile Tilapia heritability, obtained for body weight and body length in this study, can be used in future studies of animal breeding, intending to increase the proportion of these characteristics related with body weight. Such character becomes commercially interesting when animals are sold ungutted or ready to be prepared. Probably the high heritability value, above 1.00, obtained for body weight at 60 days of age was due to a small number of data available. High heritabilities values obtained for body weight at 150 days, total body length at 60 days of age, and at 150 days of age, daily body weight gain and daily body length gain could be explained by the small environmental variation, because animals were kept on the same environmental conditions such as quantity and quality of water, feeding and management. Another explanation for the high values of the characteristics mentioned above is because of the genetic parameters estimation was made just in one generation which was not submitted to any artificial selection. Very high genetic correlations was obtained between body weight and total body length, therefore the measurement of body length is not necessary because it takes much time and it stresses the fishes. Also this technique limits to a smaller number of animals used in a genetic evaluation program of Nile Tilapia, instead a larger sample number desired. The genetic correlation of body weight at 60 days of age and ungutted carcass weight was considered low, however a high genetic correlation was obtained between ungutted carcass weight and body weight at 150 days of age. This means that is possible to obtain heavier carcasses if the selection is made in body weight characteristic.