Bi-Directional Communication: Growth and Immunity in Domestic Livestock

¹ USDA-ARS-Livestock Issues Research Unit, Lubbock, TX 79409

^* To whom correspondence should be addressed. E-mail: jacarroll{at}lbk.ars.usda.gov.

	Abstract

Evidence continues to mount supporting the existence of a 'bi-directional' communication network between the immune system and the somatotropic axis in a variety of species. For more than four decades, researchers have sought and identified linkages between the growth axis and the immune system. While significant advances have been made with regard to elucidation of various bi-directional communication pathways between the immune system and growth axis in humans and rodents, the current paper focuses on the relationships between the immune system and somatotropic axis in sheep, cattle, and swine. Aspects from both historical and current research associated with changes in somatotropic function following immune challenges with endotoxin, parasites, viruses, and bacteria have been provided. Collectively, these studies demonstrate that a bi-directional communication network, similar to that described in humans and rodents, also exists in a variety of domestic livestock. Identifying and understanding this bi-directional communication network could have significant economic benefits if it leads to intervention strategies to prevent production losses associated with sickness and disease.

Key Words: growth, cattle, immune function, pigs, cytokines, sheep