Abstract
Crossbred male beef calves (n = 259; bulls = 134, steers = 125; body weight = 250 ± 3.4 kg) approximately 6 months of age and considered high-risk for developing bovine respiratory disease arrived on 3 dates (block) and were stratified by arrival castrate status and weight to be evenly distributed across pens (8 pens/block; 9 to 12 calves/pen). The pens were randomly assigned to 1 of 2 treatments: 1) Nuplura PH (administration of a Mannheimia haemolytica leukotoxoid at processing) or 2) Control (no M. haemolytica leukotoxoid). All cattle received tilmicosin on d 0 with a 5-d post-metaphylactic interval. Body weights were recorded on d -1, 0, 14, 28, 41 and 42. Blood was collected on d -1, 14, 28, and 42 and sera were harvested to determine serum neutralization titers for bovine virus diarrhea (BVD) type I and bovine anti-M. haemolytica leukotoxin antibodies. Calves were observed daily for signs of morbidity. Body weight and average daily gain were not affected (P ≥ 0.26) by treatment. The percentage of calves administered 1, 2, or 3 antibiotic treatments for clinical bovine respiratory disease did not differ (P ≥ 0.35). There was a tendency for mortality to be greater for Control compared to Nuplura PH (1.6 vs 0.0%; P = 0.10). Calves administered Nuplura PH possessed greater antibody response against M. haemolytica leukotoxin on d 14, 28, and 42 compared to Control calves (P < 0.01). There was no treatment × day interaction for antibody titers against BVD (P = 0.98). The use of a M. haemolytica leukotoxoid had no effect on growth performance and morbidity for the 42-d following receiving in this small-pen study, but reduced the incidence of mortality and did not interfere with antibody response to BVD vaccination in high-risk, newly received calves metaphylactically treated with tilmicosin on arrival.
Association of plasma haptoglobin concentration and other biomarkers with bovine respiratory disease status in pre-weaned dairy calves
