Bovine respiratory disease (BRD) remains the leading cause of feedlot calf sickness and death. In respiratory disease affecting humans and mice, major tissue damage is caused by release of histones. Histones are proteins found in the nucleus of cells that condense DNA, however, cells that become damaged release histones extracellularly. Research has shown that calves with severe cases of BRD are less able to protect against the toxic effects of histones residing outside of the cell. It is speculated that components within the blood may interact with histones and confer protection from histone toxicity. This study evaluated serum from protective and nonprotective cattle against histone toxicity and identified 16 proteins that were elevated in protective animals. Several proteins were associated with the complement system of the innate immune system. To evaluate immune complement activity and protective capacity against histone toxicity, serum was collected from heifers at feedlot arrival. Calves suffering from a severe case of BRD demonstrated reduced capacity to protect against histone toxicity. Complement activity of calves severely affected with BRD was reduced as well. Results suggest that cattle susceptible to severe cases of BRD may have impaired complement activity likely contributing to reduced protective capacity against histone toxicity.

Read the full article in the Journal of Animal Science.