TDK conference 2020

Supplementation of the constantly growing human population requires food production operating with the highest efficiency possible. Hence, specific needs and welfare of farm animals are getting considered more important. By virtue of global warming and in correlation, more frequently appearing intense heat waves, mechanism of heat stress response comes more into focus of agriculture. High environmental temperatures impair normal cell function and damage cellular elements through numerous different pathways. These cellular changes have been already studied in several point of view; however, exact mechanisms behind negative effects are often still unknown. Therefore, our current research focuses on the effects of acute heat stress on parenchymal organs of broiler chickens in vivo.

The 32-day old, Ross 308 broiler chickens have been exposed to a temperature of 37°C for 4 and 8 hours, respectively. Decapitation was carried out in a carbon-dioxide narcosis, thereafter samples were collected from liver, spleen and kidney. In order to study the impact of heat stress on cellular level, first, we evaluated quantitative changes of small heat shock proteins Hsp27, alpha-B-crystallin (HspB5) and alpha-A-crystallin (HspB4) by chicken specific ELISA tests. Furthermore, redox state of the cells was examined. Changes of malondialdehyde and protein carbonyl concentrations, as well as glutathione peroxidase enzyme activity were monitored which factors are well-known biomarkers of oxidative stress related injuries.

Our results show a significant decrease in the concentrations of alpha-A and alpha-B-crystallin in the liver following both heat exposure time, whilst concentrations in the other organs remained unchanged. Regarding Hsp27, there were no significant alterations in any of the organs. In the liver, protein carbonyls showed significant decrement as the effect of both the shorter and longer treatments, while in the spleen, the decrease was only observable following the longer exposure time. After the 8-hour heat stress treatment, we also experienced increased malondialdehyde concentrations and higher activity of glutathione peroxidase enzyme in the liver.

In our presented study, molecular effects of heat stress in various organs of broiler chicken were observed from a novel point of view. Similar to studies using other animal species, single-time occuring, acute heat stress resulted in the decrease of protein carbonyl content. Supposedly, this occured due to an increased utilization of small heat shock proteins induced by increased cellular oxidative stress, resulting in an overcompensating mechanism. Nevertheless, longer term heat stress would probably result in higher protein carbonyl concentrations as not even the further increasing small heat shock protein production could alleviate with the grade of protein oxidation and provide sufficient cellular protection.