Paratuberculosis is associated with a long latent period of infection before clinical signs of disease develop. Stressors may influence the progression to more clinical disease in infected animals. Stress such as parturition and lactation may result in significant suppression of host immunity. This may contribute to the progression of Johne's disease from a subclinical to more clinical state in cows following the periparturient period. The present study was designed to evaluate if feeding supplemental energy to dairy cows during the periparturient period would alleviate some of the immunosuppression typically noted and ultimately allay presentation of clinical signs of paratuberculosis. Twelve dairy cows in late gestation were assigned to a treatment group receiving silage (n = 6) or silage plus additional feed (n = 6). Diets were fed for 3 weeks pre- and post-calving and blood and fecal samples were obtained 2 days per week during the 6-week period. Milk samples were obtained each day during the 3 weeks post-calving. Lymphocyte blastogenesis, in vitro Ig production, neutrophil iodination and IFN-g were performed on blood samples. Flow cytometric analysis for homing receptors on immune cells was performed on blood and milk samples. Fecal and milk samples were cultured for viable organisms using HEYM and BACTEC. Parturition reduced immune function with notable reductions in all immune function tests including neutrophil assays, ELISA, IFN-g, lymphocyte blastogenesis, and in vitro Ig production. Expression of LPAM-1, a mucosal homing receptor, was reduced on blood T cell subsets after calving but increased on milk T cell subsets. Energy supplementation moderated cell-mediated immunity by reducing lymphocyte blastogenesis and IFN-g production but enhanced neutrophil iodination during the periparturient period. These data suggest that parturition has a significant effect on immune function parameters including diagnostic tests for paratuberculosis and energy supplementation did not preclude the immunosuppression during the peripaturient period.tion did not preclude the immunosuppression during the peripaturient period.