Hyperimmune serum containing Histophilus somni rHsp60, rOMP40 and Actinobacillus pleuropneumoniae LPS antibodies as supplementary treatment for calf respiratory diseases

Bovine respiratory disease (BRD) in dairy heifer calves cause significant economic losses associated with treatment costs, reduced growth rate and mortality. Bovine hyperimmune serum was produced in cows hyperimmunized with three conserved antigens (Histophilus somni rHsp60, H. somni rOMP40, and Actinobacillus pleuropneumoniae LPS core oligosaccharide), which exhibit broad cross-reactivity with several Gram-negative bacteria. Dairy heifer calves received serum subcutaneously on the first day of treatment for BRD, as an additive to antibiotics and anti-inflammatory drugs. Health status was estimated on a modified point scale system on days 1, 7 and 14th of the treatment. The calves were divided into four groups (10 per group): two with moderate signs of BRD, one with and one without hyperimmune serum application, and two with severe signs of BRD, one receiving hyperimmune serum. At day 1,7,14 of treatment and day 180 of age, plasma fibrinogen, serum haptoglobin, serum amyloid A, IgG₁, IgG₂, and IgM concentrations were estimated. Harvested hyperimmune serum contained high levels of IgG₁ and IgG₂ antibodies against homologous antigens. The findings suggest that the supplementary use of hyperimmune serum, in combination with antibiotics and NSAIDs, may contribute to an earlier improvement and reduced severity of clinical signs in dairy heifer calves compared to treatment without serum.