Peripheral and gastrointestinal immune systems of healthy cattle raised outdoors at pasture or indoors on a concentrate-based ration

A number of in vitro functional tests of immune cells suggested subtle differences between the animals on the outdoor versus indoor production systems. There was a decrease in the number of neutrophils and monocytes engaged in phagocytosis in outdoor cattle (P < 0.01 and P < 0.05, respectively) in comparison to those indoors. Following mitogen stimulation, a lower level of interferon-γ was produced in leukocytes from the outdoor animals (P < 0.05). There was evidence of a gastrointestinal nematode infection in the outdoor animals with elevated levels of serum pepsinogen (P < 0.001), a higher number of eosinophils (P < 0.05) and a higher level of interleukin-4 and stem cell factor mRNA expression (P < 0.05) in the outdoor animals in comparison to the indoor animals. Lower levels of copper and iodine were measured in the outdoor animals in comparison to indoor animals (P < 0.001).Despite distinctly contrasting production systems, only subtle differences were identified in the peripheral immune parameters measured between cattle raised at pasture in comparison to animals raised on a conventional intensive indoor concentrate-based production system.Emerging data suggest that there are human health advantages associated with the consumption of grass-fed beef compared with beef produced from intensive concentrate-based systems [1]. There is also some evidence that regular outdoor exercise has positive effects on the health status of cattle [2,3]. The outdoor environment may expose animals to different immune challenges in comparison to the indoor environment, but whether this leads to a differentially activated immune system has not been fully investigated. Indeed, only one research group has examined the effect of outdoor versus indoor housing on immune status and this study was performed on pigs [4]. These authors identified a lower white blood cell and lymphocyte count, accompanied by a lower natural killer cell activity and a higher neutrophil percentage in outdoor co