Relationship between Protein Nutritional Status and Immunocompetence in Northern Bobwhite Chicks

Abstract

We investigated the effects of dietary protein quality on the development and functioning of the immune system in four-week-old Northern Bobwhite (Colinus virginianus) chicks. Chicks were fed isocaloric diets containing 8, 15, or 33% protein over a three-week period. Significant reductions in the rate of body growth were evident in chicks receiving 8 and 15% protein. Development of the bursa of Fabricius and spleen was significantly depressed in the 8% protein group compared to the other two treatments. Lymphocyte yields from dissociated lymphoid organs of chicks fed 8% protein were substantially reduced compared to birds fed higher levels of protein. In vitro lymphoproliferative responses of cultured splenocytes to mitogenic stimulation (concanavalin A, pokeweed mitogen, and Salmonella typhimurium), white-blood-cell counts, and in vivo measures of humoral immunity did not differ among dietary treatments. Cell-mediated immune function, as measured by an in vivo hypersensitivity response to an intradermal injection of a T lymphocyte-dependent mitogen (phytohemagglutinin), was significantly suppressed in the 8% protein group compared to the other two treatments. Several measures of immune-system development and function were significantly correlated with body mass change during the trial. Results indicated that four-week-old Northern Bobwhite chicks fed an 8% protein diet for three weeks may have difficulty expressing a competent immune response to pathogenic challenge in the wild.