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

Abstract

Background: Despite an increasing preference of consumers for beef produced from more extensive pasture-based production systems and potential human health benefits from the consumption of such beef, data regarding the health status of animals raised on pasture are limited. The objective of this study was to characterise specific aspects of the bovine peripheral and the gastrointestinal muscosal immune systems of cattle raised on an outdoor pasture system in comparison to animals raised on a conventional intensive indoor concentrate-based system.

Results: 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-gamma 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).

Conclusion: 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.

Figure 1

Phagocytosing neutrophils and monocytes in indoor and outdoor animals. Percentage of phagocytosing neutrophils (Figure 1A) and monocytes (Figure 1B) in indoor (shaded bars) and outdoor (clear bars) animals during summer and winter. Values are depicted as mean ± SEM. P values for the treatment, season and treatment × season effects were 0.001, 0.033, 0.397, respectively, for neutrophils and 0.021, 0.652, 0.313, respectively, for monocytes.

Figure 2

Con A induced in vitro IFN-γ production from cultured leukocytes. Con A induced in vitro IFN-γ production from cultured leukocytes from indoor (shaded bars) and outdoor (clear bars) cattle during summer and winter. Values are depicted as mean ± SEM. P values for the treatment, season and treatment × season effects were 0.011, 0.023, 0.382, respectively.

Figure 3

Eosinophil and mast cell count in the abomasal mucosa. Eosinophil (Figure 3A) and mast cell (Figure 3B) counts in the abomasal mucosa of indoor (shaded bars) and outdoor (clear bars) cattle during summer and winter are depicted as mean ± SEM. P values for the treatment, localization and treatment × localization effects are 0.020, 0.001, 0.006, respectively for eosinophils and 0.093, 0.001, 0.300, respectively for mast cells.

Figure 4

Cytokine gene expression profile in the small intestine. Cytokine gene expression profile in the small intestine of indoor (shaded bars) and outdoor (clear bars) animals at slaughter. Values are depicted as mean ± SEM. * P < 0.05.