EFFECT OF THE GENETIC SELECTION OF TURKEYS FOR INCREASED BODY-WEIGHT AND EGG-PRODUCTION ON IMMUNE AND PHYSIOLOGICAL-RESPONSES

Selection of poultry for fast growth rate is often accompanied by a re duction in specific immune responses or increased disease susceptibili ty. In this study, 17-wk-old male turkeys from each of four closed gen etic lines, a randombred control (RBC) line and its subline (F) select ed for increased 16-wk BW, and another RBC line and its subline (E) se lected for increased egg production, were tested for in vivo response to toe web inoculation with phytohemagglutinin-P (PHA-P), in vitro res ponse of lymphocytes in whole blood to PHA-P and concanavalin A (Con A ), hemolytic complement activity, differential white blood cell counts , hematology, and serum chemistry values. Fifteen male turkeys from ea ch of two commercial lines, Com A and Com B, were also tested. The lar ge-bodied F line birds had a lower toe web response to PHA-P, lower ly mphocyte counts, and lower relative spleen weights than their smaller parent line. Body weights, total erythrocyte counts, blood urea nitrog en (BUN) levels, and in vitro mitogenic response to PHA-P and Con A we re higher in the F line birds. Line E had lower hemolytic complement l evels, lower relative spleen and relative bursal weights, and a higher in vitro mitogenic response to PHA-P than its parent line. The Com B line had a lower toe web response to PHA-P, and lower serum levels of gamma-glutamyltransferase and bilirubin than Com A. Line Com B had hig her total RBC counts and higher levels of alanine aminotransferase (AL T) than Com A. These results support the concept that some changes in the cell-mediated immune response, as well as other physiological chan ges that may potentially affect immune response, appear to accompany s election for faster growth.