Abstract
Growth rate is one of the economically important quantitative traits that affect carcass quantity in beef cattle. Two genes, bovine insulin-like growth factor I (IGF-I) and myogenic factor 5 (MYF5), were chosen as candidate genes for growth traits due to their important role in growth and development of mammals. The objectives of this study were to determine gene-specific single nucleotide polymorphism (SNP) markers of the IGF-I and MYF5 positional candidate genes and to investigate their associations with growth traits in Korean cattle. Genotyping of the SNP markers in these candidate genes was carried out using the single strand conformation polymorphism (SSCP) analysis. The frequencies of A and B alleles were 0.72 and 0.28 for IGF-I gene and 0.39 and 0.61 for MYF5 gene, respectively, in Korean cattle population examined. The gene-specific SNP marker association analysis indicated that the SNP genotype in IGF-I gene showed a significant association (p<0.05) with weight at 3 months (W3), and cows with AB genotype had higher W3 than BB genotype cows. The SNP genotype of MYF5 gene was found to have a significant effect (p<0.05) on the weight at 12 months (W12) and average daily gain (ADG), and cows with BB and AB genotypes had higher W12 and ADG compared with cows with AA genotype, respectively. However, no significant association between the SNP genotypes and any other growth traits was detected. The gene-specific SNP markers in the IGF-I and MYF5 candidate genes may be useful for selection on growth traits in Korean cattle. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 8 : 1061-1065)
Highlights
Korean cattle (Hanwoo) as an indigenous beef cattle are known to have an inferior ability to produce meat because of a low milk producing capacity and slow growth rate, while having a relatively favorable meat quality (Kim and Lee, 2000)
Where Yijkl is the observation of the growth traits (BW, weight at 3 months (W3), weight at 6 months (W6), weight at 12 months (W12) and ADG), μ is the overall mean for each trait, YSi is the effect of ith year and season of calving, Pj is the effect of jth parity, Gk is the fixed effect of Kth Insulin-like growth factor I (IGF-I) genotype (k = AA, AB, BB) or Myogenic factor 5 (MYF5) genotype (k = AA, AB, BB) and eijkl is the random residual effect
Mapping of QTL and identification of causative genes that affect growth traits will greatly enhance the progress towards this goal (Li et al, 2004)
Summary
Korean cattle (Hanwoo) as an indigenous beef cattle are known to have an inferior ability to produce meat because of a low milk producing capacity and slow growth rate, while having a relatively favorable meat quality (Kim and Lee, 2000). The Korean cattle industry aimed to increase meat production and to produce high quality meat to meet the increasing demand of the consumer for high quality beef. Even though the nature of genes influencing economically important traits is in general not known, genetic selection in this way has been very successful. Recent developments in molecular genetic techniques have made it possible to identify genetic variation at specific loci and the association between variation at gene affecting quantitative traits (quantitative trait loci, QTL) and production traits. Gene or marker-assisted selection (MAS) is a promising strategy for genetic improvement of economically important quantitative traits such as growth and carcass traits in beef cattle (Gerbens et al, 2000). Molecular marker-assisted selection will first require identification of candidate genes or anonymous genetic markers associated with the traits of interest. The candidate gene approach was proposed by many geneticists as a
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