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Para fins de estabelecer critérios de seleção para a raça Brahman, no Brasil, este estudo objetivou estimar parâmetros genéticos e ambiental para peso ao nascer (PN), período de gestação (PG) e perímetro escrotal aos 365 (PE365), 455 (PE455) e 550 (PE550) dias de idade e eficiências relativas de seleção indireta versus a direta para essas características. Os dados referem-se a 15 851 animais de 16 rebanhos de seis estados, participantes de um programa de melhoramento genético. Componentes de (co)variância e coeficientes de herdabilidade e de correlações genéticas e ambientais entre características foram estimados pelo método da máxima verossimilhança restrita, sob modelo animal multi-característica. No modelo, foram incluídos como efeitos fixos, grupo de contemporâneos e idade da vaca ao parto como covariável (efeitos linear e quadrático) e, como efeitos aleatórios, genético aditivo direto, ambiente permanente da vaca e resíduo. Para PN e PG considerou-se ainda o efeito aleatório genético materno. As herdabilidades estimadas para PN, PG, PE365, PE455 e PE550 foram, respectivamente, 0,36; 0,29; 0,55; 0,43 e 0,40. As correlações genéticas entre PN e PG, PG e PE365, PG e PE455, PG e PE550, PE365 e PE455, PE365 e PE550 e PE455 e PE550 foram, respectivamente, 0,06; 0,13; 0,20; 0,13; 0,96; 0,98 e 0,99. Todas as características apresentaram variabilidade genética aditiva suficiente para responder favoravelmente à seleção. No que tange a precocidade sexual, a melhor opção seria PE365, devido à alta herdabilidade estimada, além de que a seleção indireta a esta idade seria mais eficiente que a direta para PE455. Aiming to establish selection criteria for the Brahman cattle in Brazil, the objective of this paper was to estimate genetic and environmental parameters for birth weight (BW), gestation length (GL) and scrotal circumference at 365 (SC365), 455 (SC455) and 550 (SC 550) days of age, and relative efficiency of indirect versus direct selection for these traits. Data were obtained from 15 851 animals belonging to 16 herds in six states, enrolled in a genetic breeding program. (Co)variance and heritability coefficients and genetic and environmental correlations between traits were estimated by restricted maximum likelihood (REML) under a multi trait animal model. The model included as fixed effects the contemporary group and the age of cow at calving as a covariate (linear and quadratic), and as random the direct genetic, the permanent environmental and residual effects. For BW and GL it was also considered the maternal genetic effect as random. Estimates of direct heritabilities were 0.36, 0.29, 0.55, 0.43 and 0.40 for BW, GL, SC365, SC455 and SC550, respectively. Genetic correlations between BW and GL, GL and SC365, GL and SC455, GL and SC550, SC365 and SC455, SC365 and SC550 and SC455 and SC550, were respectively 0.06, 0.13, 0.20, 0.13, 0.96, 0.98 and 0.99. The heritabilities estimates for all traits indicated these show enough additive genetic variability to respond favorably to selection. For sexual precocity, the best option would be SC365, due to the high value of heritability and to indirect selection at this age being more efficient than direct selection for PE455.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:27:21Z No. of bitstreams: 0 Made available in DSpace on 2014-05-27T11:27:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-12-01 Aiming to establish selection criteria for the Brahman cattle in Brazil, the objective of this paper was to estimate genetic and environmental parameters for birth weight (BW), gestation length (GL) and scrotal circumference at 365 (SC365), 455 (SC455) and 550 (SC 550) days of age, and relative efficiency of indirect versus direct selection for these traits. Data were obtained from 15 851 animals belonging to 16 herds in six states, enrolled in a genetic breeding program. (Co)variance and heritability coefficients and genetic and environmental correlations between traits were estimated by restricted maximum likelihood (REML) under a multi trait animal model. The model included as fixed effects the contemporary group and the age of cow at calving as a covariate (linear and quadratic), and as random the direct genetic, the permanent environmental and residual effects. For BW and GL it was also considered the maternal genetic effect as random. Estimates of direct heritabilities were 0.36, 0.29, 0.55, 0.43 and 0.40 for BW, GL, SC365, SC455 and SC550, respectively. Genetic correlations between BW and GL, GL and SC365, GL and SC455, GL and SC550, SC365 and SC455, SC365 and SC550 and SC455 and SC550, were respectively 0.06, 0.13, 0.20, 0.13, 0.96, 0.98 and 0.99. The heritabilities estimates for all traits indicated these show enough additive genetic variability to respond favorably to selection. For sexual precocity, the best option would be SC365, due to the high value of heritability and to indirect selection at this age being more efficient than direct selection for PE455. Associação dos Criadores de Brahman do Brasil, Uberaba, MG Universidade Estadual Paulista (UNESP) Faculdade de Ciências Agrárias e Veterinárias (FCAV), Jaboticabal, SP Associação Nacional de Criadores e Pesquisadores, Ribeirão Preto, SP Universidade Estadual Paulista (UNESP) Faculdade de Ciências Agrárias e Veterinárias (FCAV), Jaboticabal, SP