The IGF1 gene (insulin-like growth factor 1) is a candidate gene for marker-assisted selection strategies. A single nucleotide polymorphism in the promoter region (IGF1/SnaBI) has been reported to be associated with production traits in several cattle breeds. Here, we report its allelic frequencies in Charolais and Beefmaster breeds; we confirm its association with three growth traits: weaning weight, weaning weight adjusted to 210 days and preweaning weight gain in the Charolais breed. In addition, we designed a strategy to search these breeds for new polymorphisms in four coding regions of the gene. A C/A transversion was detected in intron 4, but it was not associated with the growth traits. A single nucleotide polymorphism (IGF1/SnaBI) is proposed as a selection marker for Mexican Charolais cattle; validation of its association with weaning weight, weaning weight adjusted to 210 days and preweaning weight gain, could complement the genetic evaluations of this breed through marker-assisted management strategies.

The white-tailed deer (Odocoileus virginianus) occurs over a broad latitudinal range from South America to Canada. Thirty-eight subspecies are recogn

The Channel catfish is one of the most important freshwater fish species in North America. Conventionally their selection for genetic improvement is focused in growth related traits but not on quality traits as flavor and fatty acid deposition. The aim of this study was the sequencing of Stearoyl-CoA Desaturase (SCD) and Fatty Acid Desaturase 2 (FADS2) genes, two of main genes in the biosynthesis of long chain polyunsaturated fatty acids, for novel variation discovering as a preliminary of marker assisted broader assessment. In SCD gene, two novel synonym polymorphisms (Exon 1 and 3) and a non-synonymous Serine coding polymorphism in exon 3, were found. In FADS2, two synonymous polymorphisms (Exon 1 and 3) and multiple polymorphisms in non-coding regions were discovered . Further association analysis of these novel variations could reveal punctual effect on fatty acid deposition traits and their utility for marker assisted selection purposes.

The scrotal circumference is one of the main characteristics related to fertility of the bovine male and female. Its study through genetic and genomic tools would help to the discovery of favorable variation and genetic architecture to promote its selection. The aim of this work was to carry out a genome- wide association study using a large microarray of SNPs, to identify variations and candidate genes associated with the studied trait, for which information from 141 Charolais bulls was used. Four markers found, rs110416965, rs110130953, rs43423602 and rs29003417, showed significant association at the genome level. Three of them are found within candidate genes (RBFOX2, TTF2 and CXCL2). This information contributes to the understanding of the genetic architecture of this trait.

Maternal ability (milk and environment) in beef cattle is one of the most important traits influencing weaning weight of the calf, but amount and composition of milk produced by the dam is difficult to measure. The assessment of polymorphisms of candidate genes related to milk composition could indirectly enlighten this perspective. In the present study, the frequency of α_s1-casein 1175AG and g26181A>G; κ-casein 13068 (CSN3 AB1) and 13104 (CSN3 AB2) loci, β-lactoglobulin variants 3984GA and 5263CT, Diacyl glycerol transferase K232A, and Stearoyl CoA desaturase A702G and A762G polymorphisms were estimated in Gray and Red Brahman, Nellore, Guzerat, Gir, Indubrazil, and Sardo Negro registered sires from Mexico. Most of the documented favourable alleles were found in low frequency in most of the evaluated breeds, except for β-lactoglobulin, in which the presence of favourable alleles might represent an opportunity for marker-assisted introgression. The relevance of the findings for each variation and implications from the outcomes are discussed.