Hypothermia in newly born piglets: Mechanisms of thermoregulation and pathophysiology of death

Mortality in piglets during the perinatal period, especially the first days after birth, is frequently caused by non infectious conditions, such as hypoglucemia or low birth weight, which can be associated with hypothermia experienced at birth. The thermal stability of newborn piglets is a fundamental aspect of neonatal care, so maintaining a constant, ideal temperature will substantially reduce newborn mortality. Species-specific characteristics, such as a limited capacity for thermoregulation, low energy reserves, a lack of brown adipose tissue (BAT) (-, and environmental conditions that are adverse for the piglet around the time of birth, including the absence of a microclimate, all of them contribute to difficulties in reaching thermal homeostasis in the first hours post-birth. Shivering thermogenesis and behavioral modifications to regulate body temperature through innate mechanisms allow animals to reduce their energy expenditures. Some body postures are effective in reducing contact with the floor and also nestling are useful to avoid heat loss, and also decreases heat dissipation. Achieving optimal development of thermoregulation is a challenge that newborns must confront to successfully adapt to extrauterine life. The objectives of this review, are to discuss the adverse factors that can lead to a death event due to hypothermia by analyzing the thermoregulation mechanisms at the central and cutaneous levels, also to analyze the harmful impacts that surviving neonate piglets confront in an unfavorable thermal environment, and to describe the pathophysiological mechanisms of death caused by hypothermia.(AU)