Novel immunological approaches to improve cattle health

For years veterinarians have understood that stressful experi­ences increase disease in lightweight, recently transported and commingled cattle. Increased incidence of bovine respiratory disease (BRD) in high-risk cattle has traditionally been attrib­uted to endogenous cortisol, but in fact, increased cortisol is often not measured in cattle presumed to be stressed. While high-risk cattle are often seronegative to common respiratory viruses at receiving, field trials have confirmed they can mount significant humoral response to vaccination at arrival, indicat­ing they are not too immunosuppressed to produce antibodies. However, at-arrival vaccination of high-risk cattle is not reli­ably associated with improved health over the subsequent 60-90 days. Research indicates that stress actually increases the mag­nitude of inflammatory responses to infection or other stimuli. Taken together, these findings indicate that high BRD incidence in some high-risk cattle may be more attributable to excessive or prolonged inflammation than to immunosuppression. Re­cent studies demonstrated that high-risk cattle that nonetheless stay healthy have increased expression of genes related to pro­duction of specific pro-resolving mediators (SPM), which bring inflammatory responses to a close. Research is ongoing to de­termine whether SPM can be induced by certain management practices, genetic selection, or therapeutic or prophylactic in­terventions, to improve cattle health.