Climate resilience in small ruminant and immune system: An old alliance in the new sustainability context

Physiological and immunological responses of small ruminants are affected by heat stress in the attempt to recover animals' thermal and cellular homeostasis. This review will report scientific investigations related to the complex mechanisms triggered by small ruminants to cope with heat stress that causes perturbation at different level and organ, including endocrinal and cellular response with a bidirectional crosstalk. In particular, during heat stress exposition the role of hormones (prolactin, triiodothyronine, thyroxine, and cortisol), the immune cell reactivity, the initiation of the inflammatory response in terms of cytokines profile, the heat shock cellular response, and oxidative stress will be discussed. Some critical issues for the evaluation of biomarkers of stress resiliency and thermo-tolerance at endocrinal level, immune cell response and heat shock cellular response will be examined. A scientific debate on the effect of heat shock proteins and their use as biomarker of thermotolerance for future breeding programs in a context of climate resilient ruminant production will be proposed. Moreover, based on the latest advanced comprehension of the mechanisms involved in heat stress cellular regulation, the circulating miRNAs will be introduced as promising biomarkers for their potential crosstalking with the other inflammatory biomarkers.