How Is the Effect of Phytogenic Feed Supplementation Tested in Heat Stressed Pigs? Methodological and Sampling Considerations

Climate change will lead to increasingly hot summers where the temperature rises above the thermoneutral range of pigs; as a result, they get exposed to heat stress. One of the most damaging consequences of long-lasting heat stress is oxidative stress arising from the increasing level of reactive oxygen species. In order to eliminate oxidative stress, metabolites that are needed for maintaining life and growth may get depleted, which, in chronic cases in particular, negatively affects the economy of meat production. The effect of plant-originated phytogenic feed additives with high antioxidant content may be beneficial to pigs in reducing the effects of oxidative stress induced by heat stress. In this study, a range of methods that assess the effects of phytogenic feed additives on heat stress are reviewed. The main focus is presenting an overview of the investigational possibilities of the antioxidative system and feed uptake and utilization via traditional methods and molecular biological investigations. Furthermore, methodological aspects of sampling are taken into consideration in order to select the best methods for determining the effect of phytogenic feed supplementation on heat-stressed pigs.