Baseline immune profiles of local chicken breeds: linking biodiversity, animal health, and vaccination response

Chickens are one of the world's most important farm animals. With an increasing demand for poultry meat and eggs in recent years, chickens play an essential role in global nutrition and agriculture. However, a severe loss of genetic diversity in livestock has been caused by the focus on high-performance lines, with many traditional and local breeds being threatened with extinction. Although it is assumed that traditional local breeds are more resilient to disease and less susceptible to external influences, little is known about their immunocompetence. This study focuses on the immunological performance of three local chicken breeds (Altsteirer, Bielefelder, and Ramelsloher) in Germany. To evaluate general immunocompetence, blood samples from naïve chicken throughout their lifespan were analyzed by flow cytometry. In adult chickens, minor breed differences were detected regarding the composition of T cell subtypes. However, in day-old chicks the presence of these T cells differs greatly between breeds. To assess the immunological memory after Newcastle Disease Virus vaccination, cellular and humoral immune responses were analyzed. Both, in vivo and in vitro experiments revealed that the duration of immunity depends on the genetic background. Breed-specific proliferation phenotypes were observed up to tolerance induction in one breed after viral re-stimulation. The immune differences among local chicken breeds can explain their differential response to Newcastle Disease vaccination, providing immune markers for breed selection in organic farming. The results of the present study represent the genetic diversity of chicken breeds and show differences in the immunocompetence of local breeds. Thus, this study provides valuable insights into the genetic variation of immunological traits beyond commercial hybrids.