Effect of pig type and dietary protein level on the metabolomic pattern, feed efficiency, and GHG

The effects of dietary CP content (normal or low) and pig type on productivity, digestibility of nutrients and GHG emissions were assessed in a 98 d, 3-phase feeding program. Thirty-two castrated male Duroc (C-Du) and 32 entire male Pietrain (E-Pi) piglets were used. A digestibility trial was conducted using chromic oxide as an external marker. At the last day of each feeding, rectal spot feces and blood samples were taken. The indoor environmental and outdoors fresh air samples were sampled using syringes, which were analyzed immediately for CO2, N2O, NH3 and CH4. Feed and feces samples at each experimental phase were analyzed for DM, CP, and NDF. Non targeted chromatographic analyses of both polar and global extracts from plasma at 18 wks of age were performed with a Hypersil GOLD C18 selectivity LC column. Metabolites were eluted using a gradient of formic acid and analyzed by an Orbitrap Fusion mass spectrometer. Data were acquired for 22 min in positive and negative modes; the full mass scan range was m/z 65-1,500 with a resolution of 240,000 and a maximum injection time of 1 ms. No differences were observed in the overall ADFI, but C-Pietrain presented a higher ADG (P=0.01). DM Digestibility was higher in the low CP diets (P<0.001), and CP digestibility increased in E-Pi pigs (P=0.01). Both types showed differences in the metabolic pattern in global extracts (PERMANOVA, P<0.024 in negative mode), although this was not considered significant in the polar extracts, suggesting that the non-polar fraction of metabolites could be responsible of the metabolomic differences between pig types. Diet also influenced global metabolomics pattern (P<0.015 in negative mode), but no effect was observed for the interaction between diet and pig type. Further work identifying key metabolites related with specific metabolomics patterns will help to deepen the understanding of the link between metabolism and productive types. This study is part of the Feed-a-Gene project and received funding from the European Union’s H2020 program under grant agreement no. 633531