Abstract
The objective of this study was to identify genomic regions and metabolic pathways associated with dry matter intake, average daily gain, feed efficiency and residual feed intake in an experimental Nellore cattle population. The high-density SNP chip (Illumina High-Density Bovine BeadChip, 777k) was used to genotype the animals. The SNP markers effects and their variances were estimated using the single-step genome wide association method. The (co)variance components were estimated by Bayesian inference. The chromosome segments that are responsible for more than 1.0% of additive genetic variance were selected to explore and determine possible quantitative trait loci. The bovine genome Map Viewer was used to identify genes. In total, 51 genomic regions were identified for all analyzed traits. The heritability estimated for feed efficiency was low magnitude (0.13±0.06). For average daily gain, dry matter intake and residual feed intake, heritability was moderate to high (0.43±0.05; 0.47±0.05, 0.18±0.05, respectively). A total of 8, 17, 14 and 12 windows that are responsible for more than 1% of the additive genetic variance for dry matter intake, average daily gain, feed efficiency and residual feed intake, respectively, were identified. Candidate genes GOLIM4, RFX6, CACNG7, CACNG6, CAPN8, CAPN2, AKT2, GPRC6A, and GPR45 were associated with feed efficiency traits. It was expected that the response to selection would be higher for residual feed intake than for feed efficiency. Genomic regions harboring possible QTL for feed efficiency indicator traits were identified. Candidate genes identified are involved in energy use, metabolism protein, ion transport, transmembrane transport, the olfactory system, the immune system, secretion and cellular activity. The identification of these regions and their respective candidate genes should contribute to the formation of a genetic basis in Nellore cattle for feed efficiency indicator traits, and these results would support the selection for these traits.
Highlights
Costs associated with animal feeding can be up to 50% of the total cost in beef cattle production systems, and there is growing interest concern in adopting strategies to reduce these costs [1]
The objective of this study was to identify genomic regions and metabolic pathways associated with dry matter intake (DMI), average daily gain (ADG), feed efficiency (G:F) and residual feed intake (RFI) in an experimental Nellore cattle population
Phenotypic information is animals born from 2004 to 2012. These animals belong to three experimental lines of Nellore cattle, which have been selected since 1978 for yearling weight: selection line (NeS) is a closed herd selected for higher yearling weight; traditional line (NeT) is submitted to the same selection criterion as NeS but, eventually, receives animals from NeS; and a control line (NeC) selected for average of yearling weight [17]
Summary
Costs associated with animal feeding can be up to 50% of the total cost in beef cattle production systems, and there is growing interest concern in adopting strategies to reduce these costs [1]. Improving feed efficiency would increase both sustainability and profitability in the beef cattle industry. Selection for feed efficiency indicator traits in beef cattle can reduce production cost, decrease use of natural resources, and reduce impacts on the environment, optimizing production efficiency [2]. Selection to improve feed efficiency could increase mature weight and increase energy maintenance requirements [4]. Residual feed intake (RFI), as proposed by Koch et al [5], defined as the difference between actual feed intake and the feed intake required to meet maintenance requirements and growth, offers advantages over G:F since there is no correlation with performance traits [2, 6, 7, 8, 9]
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