Changing challenges and paradigms.

Change comes as a surprise because things do not happen in a straight line. Concepts often evolve haphazardly, reacting to specific events. Assumptions are made but are not challenged, sometimes for political or social expedience. It has long been recognized that the dose makes the poison. Concepts of the relationship evolved from both events and the availability of exploratory tools. There are consequences to risk aversion. The general concept of hormesis is perhaps not unexpected. The acceptance of multiphasic dose-responses has the potential to unleash additional and productive insights into this relationship. The activities of BELLE and its Newsletter provide an excellent example of what can be achieved when dogmas are challenged by the accrual of information that has not been previously examined to see whether additional insights are possible. A forthcoming challenge will be the critical examination of all the inputs and assumptions that will be used in the increasing sophistication of biological modeling.

Effect of transport stress on respiratory disease, serum antioxidant status, and serum concentrations of lipid peroxidation biomarkers in beef cattle.

OBJECTIVE: To determine the effect of transportation stress on serum concentrations of oxidative stress biomarkers of calves. ANIMALS: 105 crossbred beef steer calves (mean [+/-SD] body weight, 207 +/- 21.2 kg). PROCEDURE: Calves were assembled at 1 location in Tennessee, and pretransit (day -3) blood samples were collected. Calves were allotted randomly by body weight into 2 groups. Calves were transported 1,930 miles to a feedlot in Texas, and 1 group received tilmicosin phosphate (33 microg/kg, s.c.) upon arrival. Calves were weighed and blood samples collected on the day of arrival (day 1) and on days 15, 22, and 28. Calves were scored daily for signs of bovine respiratory disease (BRD). Serum total antioxidant capacity (TACA) and serum malondialdehyde (MDA) concentrations were determined. RESULTS: Transportation stress significantly decreased mean serum TACA concentrations (from 147 +/- 31.2 U/mL to 133 +/- 20.1 U/mL) and significantly increased serum MDA concentrations (from 10.9 +/- 18.3 microg/mL to 30.2 +/- 50.5 microg/mL). Calves that died had a 43% increase in serum MDA concentration on day 1, compared with calves that lived (42.2 +/- 67.0 microg/mL vs 29.4 +/- 49.4 microg/mL, respectively). Calves that had > or =3 episodes of BRD had 2-fold higher serum MDA concentrations on day 1 than healthy calves. Tilmicosin-treated calves had a 20.8% significantly greater average daily gain and significantly greater serum TACA concentration than nontreated calves on day 28. CONCLUSIONS AND CLINICAL RELEVANCE: Transportation stress increases serum concentrations of oxidative stress biomarkers that are related to episodes of BRD and mortality in calves.