Effect of three different housing systems on immune responses and body weight of chicken lines divergently selected for antibody responses to sheep red blood cells

Abstract

There is an urgent need for knowledge on the effects of alternative housing conditions on parameters of health and production in current food animals, which are usually selected for a prolonged period for production traits. Thus, it is as yet unknown, whether genotype or environmental factors, or both, are major determinants of these traits. Therefore, as a model, the effects of keeping layers in three different types of housing: solitary in battery cages (BC), on a colony basis in a barn provided with litter and perches (BPL) and free range housing with access to the outdoors (FR), respectively, on immune competence and body weight (gain) of chicken lines divergently selected for high (H line) or low (L line) antibody responses to sheep red blood cells (SRBCs), next to a random bred control (C) line were studied. Antibody responses to keyhole limpet haemocyanin (KLH), Escherichia coli lipopolysaccharide (LPS) and ovalbumin (OVA) were significantly higher in the H line as compared to the C and L lines in all three housing systems, whereas in vitro mitogenesis of peripheral blood leukocytes to concanavalin (Con) A, and body weight (BW) were significantly higher in the L line in all three housing systems. No differences between the lines were found with respect to phagocyte activity. Housing conditions affected antibody responses to KLH, i.e. birds kept solitary in BC, and birds kept in BPL systems showed significantly higher antibody responses to KLH, than birds kept in the FR system. Also in vitro T-cell responses to KLH were significantly higher in BC birds than in the FR birds, but T cell responses to Con A were higher in the FR birds. Antibody responses to KLH, but also LPS and OVA were significantly affected by a housing×time interaction. Titers to these three antigens remained at a higher level in the BC then in the FR system. Birds kept in battery cages were heavier, and produced their first eggs approximately 2 and 3 weeks earlier than birds in the BPL and the FR system, respectively. The absence in the present study of significant interactions between line and housing systems on immune competence suggests that regardless of genotype, the animals respond similarly to different environments. The modulation of the magnitude of specific, but not innate immune responses in the three lines by environmental (housing) conditions suggest that the environment may favour types of specific immune responses. In addition, our data suggest that specific genotypes and specific environments may be additive in disease resistance.