Respostas a seleção para características de desempenho em Tilápias do Nilo

• Autor(a) principal: Porto, Emília de Paiva
• Data de Publicação: 2014
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1622
• topic: Tilápias do Nilo; Oreochromisniloticus; Correlação genética; Ganho genético; Tendência genética; Herdabilidade; Maringá; Paraná; Brasil.; Nile tilapia; Oreochromisniloticus; Genetic correlation; Genetic gain; Genetic tendency; Heritability; Maringá; Paraná; Brazil.; Ciências Agrárias; Zootecnia

This work presents to estimate the genetic parameters and the correlation structure of economic traits, related to the performance (daily weight gain, weight in harvesting), with carcass yield (trunk length - obtained by the difference of standard length and head length) and body shape of the animal (width and height). Furthermore, it is intended to investigate the impact of selection practiced over three years on the performance characteristics, carcass traits and body shape of the animal. As well as to estimate the direct and indirect response to selection for each characteristic. For that, it was used information of Nile tilapia (Oreochromisniloticus) under selection in the Nile tilapia genetic improvement program of the Maringá State University in the Paraná State, grown in net-tanks from 2008 to 2010. The dataset used in the analysis was provided by Peixe Gen Group, of the Maringá State University,and contained information of 6647 animals, cultivated in net-tanks, being predicted genetic values of 8590 animals in relationship matrix, of five generations. The first two generations of the program have been produced solely for the purpose of building families and from the third generation the selection process for daily weight gain has started. A one-trait and two trait analyzes were performed to estimate (co) variance from the Animal Model using Bayesian inference by MTGSAM (Multiple Trait using Gibbs Sampler in Animal Model) program. The used models included the net-tank effects, generation and gender, common hatchery environments and common nursery environment, in addition to additive genetic effects . Heritability, the relative shares of common hatchery and nursery environment, genetic and phenotypic correlations , the Spearman correlations, the direct genetic gain for daily weight gain , and the indirect genetic gain for all other traits were estimated. To describe the behavior of genetic values in different years, genetic trends of breeding values on the basis of cultivation years were estimated by linear regression equations. Estimates of genetic correlation and posts were of high magnitude, indicating the existence of strong genetic association between the analyzed traits. The heritability estimates found for daily weight gain, weight, width, height and trunk length were 0.32; 0.32; 0.29; 0.27 and 0.29 respectively. Genetic gains obtained from genetic trends were: 6.36 %, 6.30 %, 1.62%, 1.65% and 1.51 % respectively for daily weight gain, weight ,width, height and trunk length. The direct genetic gain for daily weight gain was 7.9 %, 5.18 % and 9.43 in 2008, 2009 and 2010 respectively. The best response to indirect selection was verified to be for weight, being the values very close to the daily weight gain direct response, to the other characteristics the indirect response ranged from 0.89 % to 3.48 %. The selection for growth rate promoted genetic gain in other traits of economic interest, related to performance , carcass yield and shape of animals, due to the strong genetic association between these characteristics and daily weight gain. The genetic evaluation program of Nile tilapia has shown significant genetic gain over the years, promoting the availability of genetically superior material for the production sector.