Influence of housing on endocrine function and immune system in pregnant sows

Abstract

Regrouping of unfamiliar animals as well as individual housing can lead to social stress causing an activation of physiological stress systems that affect various immune functions. Whereas EU guidelines (2001/88/EG) impose the housing of pregnant sows in social groups by 2013, individual housing is still the most conventional housing system in numerous countries. However, the effects of different housing systems on immune functions in pregnant sows are poorly investigated. Therefore, this study aimed at characterizing endocrine and immunological responses during the second half of gestation in sows kept in different housing systems. Blood samples of pregnant sows (German Landrace) either housed in single crates ( n = 11) or in a dynamic group ( n = 22) were taken 7, 6, 4, and 2 weeks pre partum and the number of different leucocyte subpopulations, the proliferative response of lymphocytes to stimulation with concanavalin A or pokeweed mitogen as well as plasma cortisol concentrations were evaluated. Significantly higher absolute numbers of helper T cells (CD3 + CD4 + CD8 +/− ) as well as cytotoxic T cells (CD3 + CD4 − CD8 + ) were found in group housed sows at most sampling points. Proliferative lymphocyte responses to each mitogen did not differ between sows of the two housing systems. However, sows kept in single crates showed a tendency for higher cortisol concentrations 7 weeks pre partum and significantly higher cortisol concentrations two weeks before parturition. In summary, these results indicate substantial effects on the neuroendocrine-immune system of pregnant sows depending on the housing system, which might affect their ability to deal with infection.