Search

The objective of this study was to perform a genomewide association study (GWAS) for growth traits in Charolais beef cattle and to identify SNP markers and genes associated with these traits. Our study included 855 animals genotyped using 76,883 SNP from the GeneSeek Genomic Profiler Bovine HD panel. The examined phenotypic data included birth, weaning, and yearling weights as well as pre- and postweaning ADG. After quality control, 68,337 SNP and 823 animals were retained in the analysis. The association analysis was performed using the principal components method via the egscore function of the GenABEL version 1.8-0 package in the R environment. Eighteen SNP located in 13 BTA were associated with growth traits ( < 5 × 10). The most important genes in these genomic regions were (), (), (), (), and ( [angiotensinase C]), due to their relationships with perinatal and postnatal survival, bone growth, cell adhesion, regulation of adipogenesis, and appetite. In conclusion, this study is the first to describe a GWAS conducted in beef cattle in Mexico and represents a basis for further and future research. This study detected new QTL associated with growth traits and identified 5 positional and functional candidate genes that are potentially involved in variations of the analyzed traits. Future analyses of these regions could help to identify useful markers for marker-assisted selection and will contribute to the knowledge of the genetic basis of growth in cattle and be a foundation for genomic predictions in Mexican Charolais cattle.

The insulin-like growth factor-1 (IGF-1) plays a key role in muscle development and has been described in several studies as a candidate marker gene for growth traits in farm animals. The aim of the study was to investigate IGF-1 single nucleotide polymorphisms (SNPs) at the 5’ flanking region and their association with gene expression levels and phenotypic characteristics in lambs. The experiment was executed in two phases. First, a 265 bp-long region of gDNA localized up-stream of the IGF-1 gene was scanned for SNPs by sequencing. Sequence analysis revealed that animals with low IGF-1 plasm concentration had nucleotide changes from Guanine (G) to Cytosine (C) at position 85 (85G >C), and from G to Adenine (A) at position 87 (87G >A). A PCR-RFLP protocol was set up to accomplish allelic discrimination in 22 lambs sired by Dorper rams. The frequency of the variant-carrier lambs was 50 %. The statistical analysis showed differences (P < 0.05) between carrier and non-carrier female lambs for IGF-1 concentration at 13 d (168.76 ± 15.01 vs 229.95 ± 16.78), 41 d (191.02 ± 38.28 vs 324.50 ± 42.80) and 69 d (209.18 ± 30.63 vs 375.87 ± 34.2) of the feeding trial. Statistical differences (P < 0.05) were also found for total weight gain (22.16 ± 1.07 vs 26.75 ± 1.2). In a second phase, 55 Dorper females were genotyped, then 2 homozygotes, 5 heterozygotes and 5 wild-type for the variant were randomly selected for IGF-1 qPCR gene expression analysis. Gene expression was higher (fold-change 2.6) in non-carrier animals (P < 0.05). Nevertheless, daily weight gain and weight at 150 d were not statistically significant. The variant for the IGF-1 gene here reported has lower levels of gene expression. However, additional experiments are needed to measure phenotypic characteristics such as carcass traits, diameter and density of muscle fibers.