The feasibility of molecular markers in animal production

In animal breeding programs, molecular markers can be used to select individuals with better phenotypes. The perspectives for the enhancement of the production indexes are associated with the use of genotyping through molecular biology methods. Furthermore, the advances in statistics and bioinformatics promoted significant progress in the quality of the animal productive chain. Molecular markers are important tools to identify the genetic variation between individuals. In addition, these methods may be used to detect the genetic variation of a trait of interest. In this way, the use of DNA markers permits the identification of the genetic potential of an animal before its expression as a phenotype. 1. General considerations Nowadays, the molecular biology is an essential tool for animal phenotype and genotype investigation. New strategies of management, combined with the employment of efficient genetic methods in cattle genetic improvement programs, allowed increased genetic gains that maximized the decision-making processes. In this way, these techniques influence the breedings and focus on the development of the animal production (Singh et al., 2014). The genomic information of cattle has a high predictive value because it enables the identification of animals with better productive potential. In this sense, the data obtained from molecular markers stand out with important information about the selection programs and genetic improvement, being commonly referenced as molecular markers assisted selection (Teneva, 2006). Additionally, the search for molecular markers promotes a significant advance in the genetic improvement of commercial species destinated to the animal production, in particular by the increase in the prediction accuracy of genetic value for the superior animal selection. Populational-genetic parameters (allele and genotype frequency estimation) permit the comparison of rates between populations and show differences in their genetic compositions, in which they contribute to the phenotypic variation (Pereira et al., 2015). On the other hand, some studies have shown the possibility to map genes and their groups that may influence quantitative traits (Quantitative Trait Loci – QTL). The QTLs are identified by detecting genes that are directly related to production characteristics, called candidate genes. Additionally, the QTLs are identified by random markers in the development of saturated genetic maps. These markers correlate with the traits of economic interest and describe the chromosomal regions with a locus that influences the QTLs (Alencar, 2004). In cattle, the genetic polymorphisms have been associated with many characteristics of economic interest, such as weight gain in a particular age of the animal, fat content in milk, carcass quality, meat softness, lactation, and feeding conversion. The genetic polymorphisms can be microsatellites, insertion-deletion (INDEL), copy number variation (CNV) and the most recently described, the single nucleotide polymorphism (SNP), which represents the most important source of genetic variability in the genome (Gibson & Muse, 2004; Caetano, 2009; Yang et al., 2013). Some factors influence the crescent interest in the use of the SNPs as markers for genetic analysis. SNPs are abundant in the genome and, because of this, are considered as a useful tool for the program of cattle selection, paternity tests, and association with the animals’ phenotypes. Moreover, SNPs are localized in codifying and regulatory regions that may affect the expression of mutant proteins. As described, SNPs are directly responsible for the variations between individuals with traits of interest for zootechnicians (Maeda et al., 1989).