Fig. 1

Unique biological characteristics of swine that differ from livestock ruminant species. Pigs possess no brown adipose tissue (BAT), limited ketogenesis, and a limited amount of fetal fats, which result in a low rate of thermogenesis during the neonatal period. Both uterine insufficiency and large litter size due to genetic selection contribute to intrauterine growth restriction. With a large number of piglets and no increase in the lactation performance of sows, milk consumption by them is inadequate for their maximum survival and growth. Failure to maintain body temperature or receive adequate nutritional support results in the high rates of morbidity and mortality in neonatal pigs. On the other hand, pigs are susceptible to heat stress due to their lack of functional sweat glands, and, therefore, exhibit the enhanced production of oxygen free radicals in response to high ambient temperatures. Their oxidative stress and lack of BAT promote fat deposition in the body. Both oxidative stress and mortality decrease feed efficiency in pigs. The signs “↓” and “↑” denote decrease and increase, respectively