Parâmetros genéticos e tendências genéticas e fenotípicas para características produtivas e de conformação na fase pré-desmama em uma população da raça Aberdeen Angus

Abstract

RESUMO -Com os objetivos de estimar parâmetros genéticos e avaliar a tendência genética e a fenotípica para as características peso ao nascer (PN), ganho médio diário do nascimento à desmama (GMDND), peso à desmama ajustado para 205 dias (P205) e para os escores visuais de conformação, precocidade, musculatura e tamanho, na fase pré-desmama, foram utilizados 23.176 registros de animais da raça Aberdeen Angus, nascidos entre 1994 e 2004. Os componentes de (co)variância foram estimados pelo REML, utilizando-se um modelo animal. As herdabilidades diretas variaram de 0,10 (musculatura) a 0,27 (PN) e as maternas, de 0,07 (GMDND) a 0,21(P205). As correlações genéticas entre GMDND e os escores visuais variaram de 0,55 a 0,66 e para os escores visuais entre si, de 0,50 a 0,92. As tendências genéticas para PN, GMDND, P205 foram 17,5; 1,1 e 220,9 (g/ano) e para os escores visuais as tendências genéticas foram próximas de zero; as fenotípicas foram 29,8; -3,3 e 467,9 (g/ano). As herdabilidades diretas estimadas sugerem ser possível obter ganho genético por meio da seleção, embora com pequeno ganho para os escores visuais. As correlações genéticas entre GMDND e os escores visuais indicam que a seleção para a primeira promove melhoria nos escores visuais e vice versa.As tendências genéticas indicam progresso genético, porém, as fenotípicas, negativas para algumas características, sugerem a necessidade de melhorias nas condições de ambiente para viabilizar a expressão do genótipo.Palavras-chave: avaliação genética, bovinos de corte, correlação genética, escores de avaliação visual, herdabilidade, progresso genético Genetic parameters and genetic and phenotypic trends for pre-weaning productive and conformation traits for an Aberdeen Angus breed populationABSTRACT -To estimate genetic parameters and to evaluate the genetic and phenotypic progress for the traits birth weight (PN), average daily gain from birth to weaning (GMDND), weaning weight adjusted to 205 days of age (P205) and the visual scores for conformation, precocity, musculature and size, at the pre weaning phase, there were The genetic trends for PN, GMDND, P205 were 17.5, 1.1, 220.9 (g/year) and for the visual scores were almost zero; the phenotypic were 29.8, -3.3, 467.9 (g/year). The estimated direct heritabilities suggest that it can be possible to get genetic gain by selection in this population, although for the visual scores the gain will be low. The genetic correlations between GMDND and visual scores show that selection for GMDND promotes improvement in visual scores and vice-versa. The genetic trends indicate genetic progress, however the phenotypic, negatives for some traits, suggest the necessity of to improve environmental conditions.

Genetic parameters and phenotypic and genetic trends for weight at weaning and visual scores during this phase estimated for Angus-Nellore crossbred young bulls

“…The direct genetic trend (Figure 2a) was 221.0 g/year, with value higher than those obtained by Corrêa et al (2006) for the Devon breed, of 55.1 g/year, but similar to that of 220.9 g/year obtained by Weber et al (2009) for the Aberdeen Angus breed, indicating that the direct genetic gain in the years studied in this population is improving. The maternal genetic trend found in this study was -312.0 g/year, lower than that reported by Corrêa et al (2006) for the Devon breed (-23.6 g/year).…”

“…This behavior has been observed in several breeds, as pointed out by Forni et al (2007), who found similar gains in this study for conformation, musculature and precocity of the order of 0.013, 0.018 and 0.022, respectively, representing 0.42; 0.60 and 0.67% of the mean phenotypic of these traits in the Nellore breed. Weber et al (2009) had lower results for the Aberdeen Angus breed, with estimates of conformation, musculature and precocity of 0.0046; 0.0044 and 0.003, respectively, for the annual genetic gain, representing 0.15; 0.14 and 0, 09% of the mean phenotype.…”

Correlações genéticas entre escores visuais e características reprodutivas em bovinos Nelore usando inferência bayesiana

“…Em bovinos de corte, os escores visuais têm sido utilizados com o objetivo principal de identificar indivíduos com maior precocidade de terminação, melhor musculatura e conformação frigorífica, e sem tamanho excessivo na maturidade (Faria et al, 2009a;Weber et al, 2009). Trabalhos sobre a estimação dos coeficientes de herdabilidade demonstraram que os escores visuais são herdáveis (Koury Filho et al, 2009).…”

Finishing precocity visual score and genetic associations with growth traits in Angus beef cattle

“…Therefore, it should be considered in this breed genetic evaluation. Weber et al (2009a) obtained lower heritability estimates for visual scores of weaning precocity, both for the direct (0.12) and maternal (0.08) effects when they evaluated data from an Angus population that was established in Rio Grande do Sul. Similar values were obtained for precocity scores (0.16) by Costa et al (2008) with Brangus cattle; however, these authors did not include the maternal effect in the analyses.…”

“…This score considers subcutaneous fat deposition and permits the evaluation of early or late finishing. In general, finishing precocity scores have medium to high heritability (Cardoso et al, 2001;Weber et al, 2009a;Boligon and Albuquerque, 2010), indicating the possibility of obtaining genetic gain by selection. Nonetheless, few studies have estimated the genetic correlations between the finishing precocity and other traits of interest.…”