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The negative impact of heat stress (HS) on the production performances in pig faming is of particular concern. Novel diagnostic methods are needed to predict the robustness of pigs to HS. Our study aimed to assess the reliability of blood metabolome to predict the sensitivity to chronic HS of 10 F1 (Large White × Creole) sire families (SF) reared in temperate (TEMP) and in tropical (TROP) regions (n = 56±5 offsprings/region/SF). Live body weight (BW) and rectal temperature (RT) were recorded at 23 weeks of age. Average daily feed intake (AFDI) and average daily gain were calculated from weeks 11 to 23 of age, together with feed conversion ratio. Plasma blood metabolome profiles were obtained by Nuclear Magnetic Resonance spectroscopy (1HNMR) from blood samples collected at week 23 in TEMP. The sensitivity to hot climatic conditions of each SF was estimated by computing a composite index of sensitivity (Isens) derived from a linear combination of t statistics applied to familial BW, ADFI and RT in TEMP and TROP climates. A model of prediction of sensitivity was established with sparse Partial Least Square Discriminant Analysis (sPLS-DA) between the two most robust SF (n = 102) and the two most sensitive ones (n = 121) using individual metabolomic profiles measured in TEMP. The sPLS-DA selected 29 buckets that enabled 78% of prediction accuracy by cross-validation. On the basis of this training, we predicted the proportion of sensitive pigs within the 6 remaining families (n = 337). This proportion was defined as the predicted membership of families to the sensitive category. The positive correlation between this proportion and Isens (r = 0.97, P < 0.01) suggests that plasma metabolome can be used to predict the sensitivity of pigs to hot climate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]