Efeito do tamanho efetivo e de sistemas de acasalamento no incremento de endogamia em populações sob seleção, utilizando-se simulação

• Ano de defesa: 2005
• Autor(a) principal: Pereira Filho, José
• Orientador(a): Euclydes, Ricardo Frederico
• Banca de defesa: Lopes, Paulo Sávio , Torres, Robledo de Almeida , Ribeiro Junior, José Ivo , Carneiro, Pedro Crescêncio Souza
• 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: Melhoramento genético; Consanguinidade; Acasalamento; Simulação
• Palavras-chave em Inglês: Animal breeding; Heritability; Animal mating; Computer simulation
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS
• Link de acesso: http://locus.ufv.br/handle/123456789/5840

Data simulated through the GENESYS program (EUCLYDES, 1996) were used in order to evaluate the effect of four effective sizes, four kinds of mating, ando two selection systems on the Inbreeding coefficient after five, ten and thirty selection generations. It was simulated a genome with 30 pairs of autosomic chromosomes with 400 diallelic quantitative loci and only the additive effects of genes. Two base-populations were created with a single quantitative characteristic with heritabilities,0,10 and 0,50. From these base-populations, two initial populations were obtained, which originated the selection populations. These populations were selected based on the individual selection (SI) and on the best linear unbiased prediction (BLUP) and submitted to four kinds of mating: a) reproducers were randomly mated (RAA); b) exclusion of mating between full sibs and half-sibs (EICMI); c) the best males with the best females (MMMF); and d) compensatory mating (AC). The effective sizes of populations used were (Ne): TE1=30, TE2=60, TE3=120, and TE4=240 and the numbers of males selected, per generation, were (Nm): 10, 20, 40 and 80, while the numbers of females were (Nf): 30, 60, 120 and 240, which correspond, effectively, to the effective sizes. For all populations selected, the value of the sexual ratio (d=Nf/Nm) was 3 and the intensities of selection were im=1,51 for the males and if =0,80 for the females. Each female had four descendents, totalizing 120, 240, 480 and 960 indivíduals per generation. The process of selection was simulated for 30 consecutive generations and, in order to minimize the effects of the genetic oscillation , 20 repetitions were performed, per generation. The average inbreeding coefficient, the average phenotypic values and the BLUP efficiency were the genectic parameters evaluated. The BLUP was the selection method which obtained the highest genetic gains and presented the highest average inbreeding coefficients. The BLUP efficiency was higher than the efficiency of the individual selection, mainly in the low heritability (h²=0,10). The population effective size was the most influential factor for the inbreeding coefficient, in which the inbreeding increments decreased as size increased, with the smallest values obtained in the populations with the effective size Ne=240, after 30 selection generations. The mating system of the best males with the best females (MMMF) presented the highest values of average inbreeding after 30 selection generations by BLUP, followed by the system of randomly mated reproducers (RAA), after which came the system which does not allow mating between full sibs and half-sibs (EICMI). The compensatory mating system (AC) was the most efficient in avoiding the increase of average inbreeding populations, mainly using the BLUP methodology in the high heritability characteristic (h²=0,50), presenting a small dicrease in the average phenotypic value, compared to the other mating systems.