title: Correlated changes in body shape after five generations of selection to improve growth rate in a breeding program for Nile tilapia Oreochromis niloticus in Brazil.
abstract: Body shape is a commercial trait of great interest as it impacts profit and productivity of aquaculture enterprises. In the present study, we examined correlated changes in two measures of body shape (depth to length ratio, DL-R and ellipticity of mid sagittal plane, EL-H) from a selection program for high daily weight gain in a Nile tilapia population reared in freshwater cages in Brazil. Genetic parameters for body shape and its genetic association with growth traits (body weight and daily gain) were also estimated from 8,725 individuals with growth performance recorded over five generations from 2008 to 2013. Mixed model analysis showed that the selection program resulted in substantial improvement in growth performance (about 4 % genetic gain per generation or per year) and also brought about trivial changes in body shape. The heritabilities ranged from 0.470 to 0.564 for growth traits and 0.180 to 0.289 for body shape. The common family effects were low for all traits studied, accounting for only 3-11 % of total phenotypic variance. The genetic correlations between body shape and growth traits were weak, i.e., -0.385 between EL-H and growth traits and 0.28 between DL-R and body weight or daily gain. Strong and negative genetic association was found between the two body shape traits (rg = --0.955). Harvest body weight and daily gain are essentially the same traits, as indicated by the close to one genetic correlations between the two characters. Our results demonstrated that the selection process to increase growth rate had small, but slowly constant effect in body shape traits; and in the long term, the fish would have become rotund.
authors.affiliation: Universidade Estadual de Maringá, Avenida Colombo, 5790, Jardim Universitário, 87020-900, Maringá, Paraná, Brazil. caloliveira@uem.br.
authors.forename: Carlos Antonio Lopes
authors.initials: CA
authors.lastname: de Oliveira
authors.affiliation: Universidade Estadual de Maringá, Avenida Colombo, 5790, Jardim Universitário, 87020-900, Maringá, Paraná, Brazil.
authors.forename: Ricardo Pereira
authors.initials: RP
authors.lastname: Ribeiro
authors.affiliation: Universidade Estadual Júlio Mesquita Filho - FCAV/Jaboticabal, Via de Acesso Prof. Paulo Donato Castellane s/n, 14884-900, Jaboticabal, SP, Brazil.
authors.forename: Grazyella Massako
authors.initials: GM
authors.lastname: Yoshida
authors.affiliation: Aquaamerica Company, Rodovia BR 491 - km 158 Fazenda Porto, 37130-000, Alfenas, Minas Gerais, Brazil.
authors.forename: Natali Miwa
authors.initials: NM
authors.lastname: Kunita
authors.affiliation: Aquaamerica Company, Rodovia BR 491 - km 158 Fazenda Porto, 37130-000, Alfenas, Minas Gerais, Brazil.
authors.forename: Gabriel Soriani
authors.initials: GS
authors.lastname: Rizzato
authors.affiliation: Faculdade de Ciências Agrárias Universidade Federal da Grande Dourados, Caixa Postal - 533, 79.804-970, Dourados, Mato Grosso do Sul, Brazil.
authors.forename: Sheila Nogueira
authors.initials: SN
authors.lastname: de Oliveira
authors.affiliation: Universidade Federal da Bahia, Escola de Medicina Veterinária e Zootecnia, Avenida Adhemar de Barros, Ondina, 40170-110, Salvador, Bahia, Brazil.
authors.forename: Alexandra Inês
authors.initials: AI
authors.lastname: Dos Santos
authors.affiliation: The University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD, 4558, Australia.
authors.forename: Nguyen Hong
authors.initials: NH
authors.lastname: Nguyen
mesh_terms: D000818:Animals; D017756:Aquaculture; D049628:Body Size / Q000235:genetics*; D001938:Brazil; D001947:Breeding; D023681:Cichlids / Q000235:genetics / Q000254:growth & development*; D005260:Female; D016014:Linear Models; D008297:Male; D010641:Phenotype; D012641:Selection, Genetic; D015430:Weight Gain
keywords: Body depth; Daily gain; Genetic correlation; Heritability; Rotund fish
references.citation: Front Genet. 2014 Aug 04;5:251
references.pmid: 25140172