Estudo Genético-Quantitativo de Características de Crescimento Pré-Desmama de Bovinos de Corte de Diferentes Composições Raciais
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Data
2020-09-21
Autores
Caetano, Záfia Cristina Pottmaier
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Universidade Estadual Paulista (Unesp)
Resumo
RESUMO- O cruzamento entre raças é uma estratégia de melhoramento importante, pois permite explorar as diferenças genéticas entre as raças e adequar o tipo de animal ao ambiente. Contudo, é necessário que se estimem efeitos aditivos e não-aditivos de raças sobre características de produção nas populações de animais cruzados, tanto para delinear programas de cruzamento entre raças como para a obtenção de parâmetros genéticos e valores genéticos de animais no processo de seleção. Este trabalho teve o objetivo de avaliar efeitos genéticos sobre características de crescimento pré-desmama de animais provenientes do cruzamento entre raças bovinas de corte. Foram utilizados dados de pesos ao nascimento (PN) e à desmama (PD) e ganho de peso do nascimento à desmama (GDP) de animais Nelore e de vários grupos genéticos cruzados envolvendo a raça Nelore (Zb) e raças taurinas britânicas (Tb; Angus e Hereford), continentais (Tc; Charolesa, Limousin, Pardo Suíço tipo carne e Simental) e adaptadas (Ta; Bonsmara e Senepol), e raças compostas Canchim (5/8 Charolês + 3/8 Zebu) e Brangus (5/8 Angus + 3/8 Zebu). Foram avaliados os efeitos de classe de grupo genético do bezerro (CGG; combinação de raças taurinas britânicas, continentais e adaptadas com a raça Nelore) sobre as características estudadas, estimados os efeitos aditivos diretos e heteróticos individuais dos vários grupos de raças envolvidos e obtidos parâmetros genéticos (herdabilidade e correlações genéticas) para as características. Os resultados mostraram que houve efeito significativo de CGG sobre todas as características e que, em geral, os animais cruzados foram mais pesados e ganharam mais peso do que os Nelore, indicando que o cruzamento da raça Nelore com raças taurinas pode ser usado para produzir bezerros bem desenvolvidos até o desmame. Os efeitos aditivos diretos de raças taurinas adaptadas, britânicas e continentais, em relação ao Nelore, bem como seus feitos heteróticos individuais em combinação com a raça Nelore e entre si, sugerem a utilização dessas raças no sistema de produção em cruzamento com a raça Nelore. As estimativas de herdabilidade foram iguais a: 0,33 ± 0,04 (PN); 0,32 ± 0,04 (PD) e 0,28 ± 0,03 (GDP), sugerindo a possibilidade de obtenção de resposta à seleção para essas características. As estimativas de correlações genéticas foram iguais a: 0,33 para PN e GDP; 0,47 para PN e PD e 0,94 para PD e GDP, sugerindo que a seleção para qualquer uma das características deverá resultar em progresso nas outras, principalmente para PN e PD e PD e GDP.
ABSTRACT- Crossbreeding is an important strategy to improve beef production, since it allows to explore the genetic differences among breeds and to fit animal type to environmental resources. However, it is necessary to estimate additive and nonadditive breed effects on economic traits in crossbred populations, to build crossbreeding programs and to obtain accurate genetic parameters for selection purposes. The objective of this study was to evaluate genetic effects on preweaning growth traits of crossbred beef cattle. Data on birth (BW) and weaning (WW) weight and average daily gain from birth to weaning (ADG) of animals of several genetic groups involving indicine (Nellore) and British (Angus and Hereford), Continental (Charolais, beef type Brown Swiss, Limousin and Simmental) and Sanga (Bonsmara and Senepol) taurine breeds, and the composite Canchim (5/8 Charolais + 3/8 Zebu) and Brangus (5/8 Angus + 3/8 Zebu) breeds were used. The effects of class of genetic group (CGG; combination of British, Continental and Adapted Sanga taurine breeds with Nellore) of calf on the traits were evaluated, and additive direct and individual heterotic breed group effects and genetic parameters (heritability and genetic correlations) were estimated. The results showed that CGG had a significant effect on all traits studied, and that, in general, the crossbred calves were heavier and gained more weight than the Nellore ones. The additive direct effects of Adapted, British and Continental breeds were, in general, positive and significantly different from zero, mainly for WW and ADG, and the heterotic effects, both between taurine and indicine as between taurine and taurine breeds, were also positive and significantly different from zero. These results indicate that crossbreeding Nellore with taurine breeds can be used to produce heavier calves at weaning in southeastern Brazil, under pasture condition. The estimates of heritability, obtained from single trait analyses were equal to: 0.33 ± 0.04 (BW); 0.32 ± 0.04 (WW) and 0.28 ± 0.03 (ADG), suggesting the possibility of obtaining response to the selection for these traits. The estimates of genetic correlations, obtained from two-trait analyses, were equal to: 0.33 for BW and ADG; 0.47 for BW and WW; and 0.94 for WW and ADG. These estimates suggest that selection for any one of the traits should result in genetic responses in the others, mainly for BW and WW and WW and ADG.
ABSTRACT- Crossbreeding is an important strategy to improve beef production, since it allows to explore the genetic differences among breeds and to fit animal type to environmental resources. However, it is necessary to estimate additive and nonadditive breed effects on economic traits in crossbred populations, to build crossbreeding programs and to obtain accurate genetic parameters for selection purposes. The objective of this study was to evaluate genetic effects on preweaning growth traits of crossbred beef cattle. Data on birth (BW) and weaning (WW) weight and average daily gain from birth to weaning (ADG) of animals of several genetic groups involving indicine (Nellore) and British (Angus and Hereford), Continental (Charolais, beef type Brown Swiss, Limousin and Simmental) and Sanga (Bonsmara and Senepol) taurine breeds, and the composite Canchim (5/8 Charolais + 3/8 Zebu) and Brangus (5/8 Angus + 3/8 Zebu) breeds were used. The effects of class of genetic group (CGG; combination of British, Continental and Adapted Sanga taurine breeds with Nellore) of calf on the traits were evaluated, and additive direct and individual heterotic breed group effects and genetic parameters (heritability and genetic correlations) were estimated. The results showed that CGG had a significant effect on all traits studied, and that, in general, the crossbred calves were heavier and gained more weight than the Nellore ones. The additive direct effects of Adapted, British and Continental breeds were, in general, positive and significantly different from zero, mainly for WW and ADG, and the heterotic effects, both between taurine and indicine as between taurine and taurine breeds, were also positive and significantly different from zero. These results indicate that crossbreeding Nellore with taurine breeds can be used to produce heavier calves at weaning in southeastern Brazil, under pasture condition. The estimates of heritability, obtained from single trait analyses were equal to: 0.33 ± 0.04 (BW); 0.32 ± 0.04 (WW) and 0.28 ± 0.03 (ADG), suggesting the possibility of obtaining response to the selection for these traits. The estimates of genetic correlations, obtained from two-trait analyses, were equal to: 0.33 for BW and ADG; 0.47 for BW and WW; and 0.94 for WW and ADG. These estimates suggest that selection for any one of the traits should result in genetic responses in the others, mainly for BW and WW and WW and ADG.
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Palavras-chave
Melhoramento Genético, Genética Animal, Genética Quantitativa