Kinetics of the whole blood transcriptome in response to heat stress in pigs from two lines divergently selected for feed efficiency.

This study aims to use omics data to understand the genetic pathways involved in heat stress adaptation after a short and a long time exposure. Heat stress is one of the main performance limiting factors in the pig industry and its importance is expected to increase with the consequences of climate warming. Various solutions to mitigate the effects of heat stress on pig performance and welfare have been investigated, and genetic selection appears to be a potential solution. The genetic mechanisms behind heat tolerance are still not well understood, but some differences between breeds have been shown, as well as an interaction between genetics and environment. Here, pigs divergently selected for feed efficiency were used to assess their ability to adapt. To achieve this, transcriptomic data from whole blood were obtained in an experiment involving 12 pigs from two RFI (residual feed intake) lines, n=6 HRFI and n=6 LRFI and was carried out in two replicates. The Low RFI (LRFI) are more efficient (less residuals) and high (HRFI) are less efficient (more residuals). The pigs were 80 days old at the start of the experiment and weighed approximately 40 kg. Blood samples were collected at different time points before (24°C) and after (30°C) exposure. A final total of 75 samples were analyzed (38 for HRFI and 37 for LRFI). Seven time points were studied. Blood samples were collected five days (-5) prior heat exposure. On the day of fluctuating temperature (at 10:00), blood samples were collected at 9:00 (0_9, one hour prior to the increase in temperature), and at 13:00 and 18:00 hours (0_13, 0_18). Subsequently, blood samples were collected at 1, 2, and 13 days post-exposure.