In nature, weaning in the pig is a gradual process that occurs at about 3 months of age and represents the shift from the piglets’ reliance on sow’s milk to other food sources. However, in many modern swine production systems, weaning is an abrupt process occurring in life at around 21 or even 14 days of age. Early weaning is stressful because the piglet must rapidly adapt to dramatic changes in its social and physical environment. Such changes may affect their health and welfare through a decline in feed intake and an increase in susceptibility to disease. Therefore, the control of early weaning stress in swine production is important but challenging.

Interleukin-15 (IL-15) is highly expressed in skeletal muscle. It possesses numerous physiological functions, including regulating T-cell growth and development, muscle protein accretion, and lipid metabolism. It has been suggested as a powerful factor to counteract the effects of inflammation. However, few studies has been devoted to investigating the expression of IL-15 in early weaning piglets.

Recently, using suckling and weaning piglets as models, a team of researchers from China Agricultural University, the Institute of Subtropical Agriculture, Chinese Academy of Sciences (ISA) conducted a study to examine the development of muscle IL-15 expression at each level, that is, mRNA (via real-time PCR), protein (via immunohistochemical evaluation), and secretion (via ELISA method).

The researchers found that IL-15 expression differed in suckling piglets and in weaning piglets. In response to early weaning stress, IL-15 expression at mRNA, protein and secretion levels increased initially, and dropped soon after with a concomitant increase in body weight gain. It is speculated that IL-15 may play an important role in counteracting the effects of early weaning stress.

The research was the jointly supported by National Basic Research Program of China (2012CB124704, 2013CB127305), National Nature Science Foundation of China (31372325, 31110103909, 31330075), Key Projects in the National Science & Technology Pillar Program (2013BAD21B04), and the Chinese Academy of Science STS Project (KFJ-EW-STS-063).

The study entitled “Myokine interleukin-15 expression profile is different in suckling and weaning piglets” has been published in March 2015 of Animal Nutrition Journal, details could be found at http://dx.doi.org/10.1016/j.aninu.2015.02.005.