Effect of the genetic selection of turkeys for increased body weight and egg production on immune and physiological responses

Abstract

Selection of poultry for fast growth rate is often accompanied by a reduction in specific immune responses or increased disease susceptibility. In this study, 17-wk-old male turkeys from each of four closed genetic lines, a randombred control (RBC) line and its subline (F) selected for increased 16-wk BW, and another RBC and its subline (E) selected for increased egg production, were tested for in vivo response to toe web inoculation with phytohemagglutinin-P (PHA-P), in vitro response 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 each of two commercial lines, Com A and Com B, were also tested. The large-bodied F line birds had a lower toe web response to PHA-P, lower lymphocyte counts, and lower relative spleen weights than their smaller parent line. Body weights, total erythrocyte counts, blood urea nitrogen (BUN) levels, and in vitro mitogenic response to PHA-P and Con A were higher in the F line birds. Line E had lower hemolytic complement levels, 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 higher total RBC counts and higher levels of alanine aminotransferase (ALT) than Com A. These results support the concept that some changes in the cell-mediated immune response, as well as other physiological changes that may potentially affect immune response, appear to accompany selection for faster growth.

Costs of Franklin’s ground squirrel (Poliocitellusfranklinii) ectoparasitism reveal adaptive sex allocation

“…Similar negative associations have been identified between immune defense and growth (Nestor et al 1996;Bayyari et al 1997;Ots et al 2001), suggesting that factors that increase investment in immune function come at the expense of other life history components.…”

Malabsorption syndrome in broilers

“…These indirect selections may result in a decrease in general resistance leading to disease susceptibility and or a bad adaptation capacity against enteric disorders. It is described that genetic selection for superior growth affects the cell mediated immune responses and the ratio of CD4+ to CD8+ T-cells in turkeys (Bayyari et al, 1997;Li et al, 2000). Thus genetic background may play a role in susceptibility to MAS.…”

Immunological basis of differences in disease resistance in the chicken

“…The immune competence correlated to a higher number of CD4 + T cell might likely represent a resistance against non-intracellular pathogens and antibody dominated response to antigens whereas CD8 + T cells might have significance in viral and intracellular infections that mainly require a cell mediated response. In turkeys, the presence of a higher number of CD4 + (or helper) T cells than CD8 + (or cytotoxic) T cells in the blood is associated with higher susceptibility to infections with Erysipelothrix rhusiopathiae, Pasteurella multocida and Newcastle disease virus [8,84]. Some studies in turkeys also correlate the susceptibility differences to erysipelas, pasteurella, and Newcastle infections with polymorphism of the CD8 molecule [83].…”