Investigation of molecular changes in the brain tissue of Transylvanian naked neck chicken caused by heat conditioning

Background: Climate change due to global warming has an increasing impact on the poultry sector. The decrease in the number of eggs, the deterioration of the meat quality of farm animals and the increase in mortality cause serious losses in farms. Many experiments have been aimed at improving heat tolerance in poultry. Literature data prove the effectiveness of heat treatment, but the molecular pathways underlying the mechanism are not fully understood yet. Objectives: The aim of our research is to investigate the defence mechanisms activated by heat treatment in brain tissue samples of chickens by comparing the expression patterns of heat shock proteins and factors, as well as miRNAs. We believe these are biomarkers of heat stress, and their investigation can help to reveal the molecular processes behind heat tolerance in animals. Materials and Methods: Fertilized eggs of Transylvanian Naked Neck Chicken were incubated at 37.5 degrees C at 60% humidity (at NBGC IFC in Hungary). After hatching, the animals of the control (C) group were kept under normal conditions. The heat treatment group (HT) was heat-conditioned (38.5 degrees C) for 12 hours at the age of 2 days, and sampling took place after treatment (chicks) and at 23-week-old. The expression of heat stress-induced genes in the brain tissues of the heat-treated and control animals were examined. Results and Discussion: Our results indicate that the expression of HSP70 in the brain tissue of 2-day-old chickens was higher in the heat-treated group than in the control group. Lower miR-138 expression was observed in heat-treated adult male chickens compared to controls. We found that miR-138 is a suitable biomarker for signalling path kays involved in heat stress, such as HSP70. As a next step, there are plans to conduct microarray analysis of microRNAs to search for heat-related miRNAs in the upcoming generation.