Abstract
The molecular mechanisms underlying feed efficiency need to be better understood to improve animal efficiency, a research priority to support a competitive and sustainable livestock production. This study was undertaken to determine whether pig blood transcriptome was affected by differences in feed efficiency and by ingested nutrients. Growing pigs from two lines divergently selected for residual feed intake (RFI) and fed isoproteic and isocaloric diets contrasted in energy source and nutrients were considered. Between 74 and 132 days of age, pigs (n = 12 by diet and by line) received a regular diet rich in cereals and low in fat (LF) or a diet where cereals where partially substituted by lipids and fibers (HF). At the end of the feeding trial, the total number of white blood cells was not affected by the line or by the diet, whereas the red blood cell number was higher (P<0.001) in low RFI than in high RFI pigs. Analysis of the whole blood transcriptome using a porcine microarray reveals a higher number of probes differentially expressed (DE) between RFI lines than between diets (2,154 versus 92 probes DE, P<0.01). This corresponds to 528 overexpressed genes and 477 underexpressed genes in low RFI pigs compared with high RFI pigs, respectively. Overexpressed genes were predominantly associated with translational elongation. Underexpressed genes were mainly involved in the immune response, regulation of inflammatory response, anti-apoptosis process, and cell organization. These findings suggest that selection for RFI has affected the immune status and defense mechanisms of pigs. Genes DE between diets were mainly related to the immune system and lipid metabolism. Altogether, this study demonstrates the usefulness of the blood transcriptome to identify the main biological processes affected by genetic selection and feeding strategies.
Highlights
Production of efficient animals is an important issue for the livestock industry [1, 2] because this implies the reduction of the amount of feed resources needed to produce meat and contributes to reduce environmental wastes and emissions
Irrespective of diet, the gain-to-feed ratio was higher in low residual feed intake (RFI) pigs than in high RFI pigs; the sum of the main fatty pieces in the carcass was lower while the sum of lean pieces was higher in low RFI pigs compared with high RFI pigs
The current study provides new evidence that the investigation of the expression of genes in whole blood allowed clear identification of biological pathways and indicator traits involved in doi:10.1371/journal.pone.0146550.g001
Summary
Production of efficient animals is an important issue for the livestock industry [1, 2] because this implies the reduction of the amount of feed resources needed to produce meat and contributes to reduce environmental wastes and emissions. Feed efficiency can be improved by breeding and feeding strategies. Residual feed intake (RFI) defined as the difference between the observed feed intake and the feed intake predicted from growth and maintenance requirements, has been studied as a measure of net feed efficiency in selection experiments [3]. Global performance differs between pigs selected for RFI, involving metabolism differences [4, 5] linked with gene expression variations in muscle [6]. The use of alternative feed resources (generally rich in fibers) that do not compete with food for humans is a challenge for the present and the future feeding strategies. Interactions between RFI genotypes and these resources can affect body composition [7, 8]. An integrated approach combining genetics and nutrition is necessary to get a better understanding of the complex biology underlying RFI and associated responses [9]
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