Estudo genético quantitativo de características de crescimento e reprodutivas em bovinos da raça Brahman no Brasil
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Data
2006-12-19
Autores
Faria, Lydio Cosac de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O presente estudo teve por objetivos principais analisar a variabilidade genética e obter estimativas de parâmetros genéticos das características de crescimento e reprodutivas a partir de um conjunto de dados oriundos de uma população de bovinos da raça Brahman no Brasil. A variabilidade genética foi determinada pela probabilidade de origem do gene e os parâmetros genéticos foram estimados pelo método da máxima verossimilhança restrita, utilizando análises uni e bi - características. O número efetivo de fundadores decresceu 75%, enquanto o número de ancestrais e genomas remanescentes tiveram um crescimento de 23%, no período de 1998 a 2005. As estimativas das herdabilidades diretas para o peso ao nascer (PN) variaram de 0,28 a 0,41, para os pesos ajustados aos 120 dias (P120), 210 dias (P210), 365 dias (P365), 455 dias (P455) e 550 dias (P550), de 0,36 a 0,52, 0,36 a 0,46, 0,40 a 0,41, 0,33 a 0,35 e 0,28 a 0,36, respectivamente. As correlações genéticas entre PN e os demais pesos variaram de 0,51 a 0,79, entre P120 e os pesos subseqüentes de 0,78 a 0,93, entre P210 e os pesos subseqüentes, de 0,98 a 0,99, entre P365 com P445 e P550, foram 0,99 e 0,98, respectivamente, e entre P455 e P550, 0,98. As estimativas de herdabilidades diretas para as características reprodutivas variaram de 0,25 a 0,35 para período de gestação (PG), de 0,09 a 0,12 para o intervalo entre partos (IEP), para os perímetros escrotais ajustados aos 365 dias (PE365) e 455 (PE455) dias, de 0,36 a 0,37 e de 0,26 a 0,27. As correlações genéticas entre PN e PG, PG e PE365, PG e PE455, PE365 e IEP, PE455 e IEP, PE365 e PE455, foram, respectivamente 0,27, 0,02, -0,03, -0,01, -0,12 e 0,99.
The present study was conducted with two major objectives: the determinative of the genetic variability and the estimation of genetic parameters for growth and reproductive traits, in a brazilian Brahman cattle population. The data were provided by Brahman Breeding Program. The genetic variability was determined by parameters based on the gene's origin probability and genetic parameters were estimated by the restricted maximum likelihood method by single and two, trait analyses. The effective number of founders decreased 75% while the ancestral numbers and the remaining genomes increased 23% in a period of 1998 the 2005. The estimates of the heritability for birth weight (BW) varied from 0.28 to 0.41, for adjusted weight at 120 days (P120) from 0.36 to 0.52, 210 days (P210) from 0.36 to 0.46, 365 days (P365) from 0.40 to 0.41, 455 days (P455) from 0.33 to 0.35, and 550 days (P550) from 0.28 to 0.36. The genetic correlations among BW and the other weights varied from 0.51 to 0.79. The correlations of P210 with the other growth traits varied from 0.98 to 0.99. Similarly, considering the, remaining growth traits the estimated genetic correlations were close to one. The direct heritability estimates for the reproductive traits varied from 0.25 to 0.35 for gestation period (GP), from 0.09 to 0.12 to age for first calving (AFC), from 0.36 to 0.37 for scrotal circumference 365 days (SC365) and from 0.26 to 0.27 to scrotal circumference at 455 days (SC455) of age. The genetic correlations among BW and GP, GP and SC365, GP and SC455, SC365 and AFC, SC455 and AFC, SC365 and SC455, were, respectively, 0.27, 0.02, -0.03, -0.01, -0,12 and 0.99.
The present study was conducted with two major objectives: the determinative of the genetic variability and the estimation of genetic parameters for growth and reproductive traits, in a brazilian Brahman cattle population. The data were provided by Brahman Breeding Program. The genetic variability was determined by parameters based on the gene's origin probability and genetic parameters were estimated by the restricted maximum likelihood method by single and two, trait analyses. The effective number of founders decreased 75% while the ancestral numbers and the remaining genomes increased 23% in a period of 1998 the 2005. The estimates of the heritability for birth weight (BW) varied from 0.28 to 0.41, for adjusted weight at 120 days (P120) from 0.36 to 0.52, 210 days (P210) from 0.36 to 0.46, 365 days (P365) from 0.40 to 0.41, 455 days (P455) from 0.33 to 0.35, and 550 days (P550) from 0.28 to 0.36. The genetic correlations among BW and the other weights varied from 0.51 to 0.79. The correlations of P210 with the other growth traits varied from 0.98 to 0.99. Similarly, considering the, remaining growth traits the estimated genetic correlations were close to one. The direct heritability estimates for the reproductive traits varied from 0.25 to 0.35 for gestation period (GP), from 0.09 to 0.12 to age for first calving (AFC), from 0.36 to 0.37 for scrotal circumference 365 days (SC365) and from 0.26 to 0.27 to scrotal circumference at 455 days (SC455) of age. The genetic correlations among BW and GP, GP and SC365, GP and SC455, SC365 and AFC, SC455 and AFC, SC365 and SC455, were, respectively, 0.27, 0.02, -0.03, -0.01, -0,12 and 0.99.
Descrição
Palavras-chave
Bovino de corte - Melhoramento genético - Pesos e medidas, Reprodução animal, Zebu, Herdabilidade, Heritability
Como citar
FARIA, Lydio Cosac de. Estudo genético quantitativo de características de crescimento e reprodutivas em bovinos da raça Brahman no Brasil. 2006. xi, 116 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Ciências Agrárias e Veterinárias, 2006.