Análise do pedigree e estimativas de parâmetros genéticos para características de importância econômica de bovinos da raça Senepol
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Data
2022-07-27
Autores
Oliveira, Ana Carolina de Jesus
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Universidade Estadual Paulista (Unesp)
Resumo
A raça Senepol possui adaptabilidade ao clima tropical e resistência à ectoparasitas. O conhecimento da estrutura da população e dos parâmetros genéticos e fenotípicos de características de importância econômica pode auxiliar no direcionamento dos acasalamentos e nos processos de seleção da raça. Os objetivos do trabalho foram avaliar e descrever a estrutura da população e estimar parâmetros genéticos para peso ajustado aos 365 dias de idade (P365), consumo alimentar residual (CAR), ingestão de matéria seca (IMS), espessura de gordura subcutânea (EG), espessura de gordura subcutânea medida na garupa (EGP8) e área de olho de lombo (AOL) de bovinos da raça Senepol. Foram utilizados 4.053 registros de pedigree e fenótipos de 2.977 animais, cedidos pelo Programa ANCP Senepol (PAS) da Associação Nacional de Criadores e Pesquisadores (ANCP). Os parâmetros populacionais foram estimados a partir de registros de pedigree utilizando o programa computacional ENDOG. As estimativas dos parâmetros genéticos foram obtidas pelo método de máxima verossimilhança restrita, utilizando o modelo animal multicaracterística por meio do programa WOMBAT, e as tendências genéticas foram estimadas por meio de regressão linear de valores genéticos para cada característica em função do ano de nascimento. A variação dos valores fenotípicos de cada característica em função da variação dos coeficientes de endogamia dos indivíduos foi realizada por meio de regressão linear. Em relação a estrutura da população, o número de gerações completas, máxima e equivalente foram iguais a 3, 10 e 4,46 respectivamente. O número efetivo de fundadores (fe) foi igual a 50 e o número efetivo de ancestrais (fa) foi igual a 35, sendo a razão entre fe e fa de 1,42. O coeficiente de endogamia médio foi igual a 0,92%. Foi observado baixo tamanho efetivo da população e relação entre fe e fa, embora coeficientes de endogamia ainda se encontrem em níveis de menor magnitude e não foi observado perdas de desempenho fenotípico em função da variação dos coeficientes de endogamia. Sugere-se atenção quanto ao uso intensivo de reprodutores e monitoramento dos níveis endogâmicos para auxiliar nos acasalamentos dos rebanhos da raça. As estimativas de herdabilidade para as características estudadas variaram de 0,16(0,08) para CAR a 0,31(0,06) para AOL e EGP8. A partir das correlações genéticas, observou-se que a seleção para P365 pode favorecer animais com maior área de olho de lombo, entretanto a seleção para P365 está fortemente correlacionado com IMS (0,93±0,14), o que sugere atenção quanto a seleção de P365 devido influenciar em animais de maior consumo de matéria seca. A importância em controlar o aumento na IMS ao selecionar P365 se justifica pelo fato de que a correlação genética entre IMS e CAR positiva e desfavorável desde que animais de CAR positivo, ou seja, aqueles que consomem mais do que o esperado. As tendências genéticas foram significativas (p<0,001), para todas as características exceto AOL e EG. Entre as características apenas P365 e EGP8 tiveram progresso genético favorável aos objetivos de seleção, sendo que observou-se mudanças genéticas desfavoráveis para CAR e IMS significativas (p<0,001). Isto pode indicar que a seleção para P365 favoreceu indiretamente animais de maior mantença e que ingerem mais matéria seca e que por sua vez favorecem animais menos eficientes para CAR. Desde que CAR possa ser mensurado, sugere-se a inclusão desta característica no índice econômico da raça, uma vez que traz benefícios do ponto de vista ambiental e financeiro.
Of recent use in the country, the Senepol breed has adaptability to the tropical climate and resistance to ectoparasites. Knowledge of population structure and genetic and phenotypic parameters of economically important traits can help guide mating and breed selection processes. Thus, this study aimed to evaluate and describe the population structure and estimate genetic parameters for adjusted yearling weight (YW), residual feed intake (RFI), dry matter intake (DMI), backfat thickeness (BF), rump fat thickness (RF) and rib eye area (REA) of Senepol cattle. A total of 4.053 pedigree records and phenotypes of 2.977 animals were used, provided by the ANCP Senepol Program (PAS) of the National Association of Breeders and Researchers (ANCP). Population parameters were estimated from pedigree records using the computer program ENDOG. Estimates of genetic parameters were obtained by the restricted maximum likelihood method, using the multitrait animal model through the WOMBAT program, and genetic trends were estimated by linear regression of genetic values for each trait as a function of year of birth. The variation of the phenotypic values of each characteristic as a function of the variation of the inbreeding coefficients of the individuals was performed by means of linear regression. Regarding the population structure, the number of complete, maximum and equivalent generations were equal to 3, 10 and 4.46 respectively. The effective number of founders (fe) was equal to 50 and the effective number of ancestors (fa) was equal to 35, with the ratio between fe and fa being 1.42. The average inbreeding coefficient was equal to 0.92%. In the present study, a low effective population size and a relationship between fe and fa were observed, although inbreeding coefficients are still at lower magnitude levels and no loss of phenotypic performance was observed due to the variation of inbreeding coefficients. It is suggested attention to the intensive use of breeders and monitoring of inbreeding levels to assist in the mating of herds of the breed. The heritability estimates for the studied traits were moderate, ranging from 0.16(0.08) for RFI to 0.31(0.06) for REA and RF. From the genetic correlations, it was observed that the selection for YW can favor animals with greater fat deposition in the rump and loin eye area, however the selection for YW is strongly correlated with DMI(0.93) and has a great influence on the effects environmental genetics, this correlation being unfavorable. The genetic correlation between IMS and CAR was positive and unfavorable, suggesting that animals with higher IMS are not selected. Genetic trends were significant (p<0.001) for all traits except AOL and EG. Among the traits, only YW and RF had genetic progress favorable to the selection objectives, it was observed unfavorable genetic changes for RFI and DMI significant (p<0.001), this may indicate that the selection for YW indirectly favored animals of greater maintenance and that ingest more dry matter and which in turn favor less efficient animals for RFI. The inclusion of the CAR characteristic in the economic index of the breed is suggested, since the reduction in food costs brings benefits from an environmental and financial point of view.
Of recent use in the country, the Senepol breed has adaptability to the tropical climate and resistance to ectoparasites. Knowledge of population structure and genetic and phenotypic parameters of economically important traits can help guide mating and breed selection processes. Thus, this study aimed to evaluate and describe the population structure and estimate genetic parameters for adjusted yearling weight (YW), residual feed intake (RFI), dry matter intake (DMI), backfat thickeness (BF), rump fat thickness (RF) and rib eye area (REA) of Senepol cattle. A total of 4.053 pedigree records and phenotypes of 2.977 animals were used, provided by the ANCP Senepol Program (PAS) of the National Association of Breeders and Researchers (ANCP). Population parameters were estimated from pedigree records using the computer program ENDOG. Estimates of genetic parameters were obtained by the restricted maximum likelihood method, using the multitrait animal model through the WOMBAT program, and genetic trends were estimated by linear regression of genetic values for each trait as a function of year of birth. The variation of the phenotypic values of each characteristic as a function of the variation of the inbreeding coefficients of the individuals was performed by means of linear regression. Regarding the population structure, the number of complete, maximum and equivalent generations were equal to 3, 10 and 4.46 respectively. The effective number of founders (fe) was equal to 50 and the effective number of ancestors (fa) was equal to 35, with the ratio between fe and fa being 1.42. The average inbreeding coefficient was equal to 0.92%. In the present study, a low effective population size and a relationship between fe and fa were observed, although inbreeding coefficients are still at lower magnitude levels and no loss of phenotypic performance was observed due to the variation of inbreeding coefficients. It is suggested attention to the intensive use of breeders and monitoring of inbreeding levels to assist in the mating of herds of the breed. The heritability estimates for the studied traits were moderate, ranging from 0.16(0.08) for RFI to 0.31(0.06) for REA and RF. From the genetic correlations, it was observed that the selection for YW can favor animals with greater fat deposition in the rump and loin eye area, however the selection for YW is strongly correlated with DMI(0.93) and has a great influence on the effects environmental genetics, this correlation being unfavorable. The genetic correlation between IMS and CAR was positive and unfavorable, suggesting that animals with higher IMS are not selected. Genetic trends were significant (p<0.001) for all traits except AOL and EG. Among the traits, only YW and RF had genetic progress favorable to the selection objectives, it was observed unfavorable genetic changes for RFI and DMI significant (p<0.001), this may indicate that the selection for YW indirectly favored animals of greater maintenance and that ingest more dry matter and which in turn favor less efficient animals for RFI. The inclusion of the CAR characteristic in the economic index of the breed is suggested, since the reduction in food costs brings benefits from an environmental and financial point of view.
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Palavras-chave
Melhoramento genético, Bovino de corte, Genética animal, Genética quantitativa, Diversidade genética