Objectives of this study were to compare the efficacy of current water-soluble and injectable antibiotic treatment regimens during naturally occurring, multi-etiologic swine disease challenges (“coinfections”) in growing pigs raised under commercial conditions and to produce a validated research protocol that can be applied by veterinarians and producers to test the value of antimicrobial treatment options under the specific conditions of their pig flows and health statuses.

Three rooms of a hotel-style, commercial nursery were modified to allow for treatment randomization. Specifically, a second water line was plumbed to allow for water medications to be assigned to individual pens rather than the whole room. Four antibiotic treatment regimens were selected prior to study initiation for comparison: 1) Whole population water 2) Whole population injection 3) Targeted injection (i.e. spot treatment) 4) Baseline (combination of population water and targeted injection). These were chosen to compare the existing treatment protocols of the collaborator to alternatives. Two studies were carried out within the three rooms. Production outcome variables were collected because these provide meaningful data to support a cost-benefit business analysis of treatment alternatives. Clinical outcome variables (i.e. response to disease, treatment success or failure, cure rate) were collected because this is the type of data that is important from a regulatory and welfare perspective. Production outcome variables included average daily gain, total mortality, 7 days post-treatment mortality, total removals, 7 days post-treatment removals, total first re-treatments, 7 days post-treatment first re-treatments, total second re-treatments, and 7 days post-treatment second re-treatments.
In one or both studies, the whole population (pen) injection treatment resulted in the lowest and statistically significant percentages of total removals, post-treatment removals with 7 days of treatment, and the frequency of re-treatments. Overall, there were no statistical differences between treatments regarding the rest of the production parameters of average daily gain, total mortality or 7 days post-treatment mortality.

Clinical outcome variables were also collected, but ultimately not reported given the clinical impact of IAV-S in both studies. IAV-S causes elevated rectal temperatures, which led to the classification of a majority of pigs as treatment failures, despite meeting all other criteria.

There are three key findings for industry: 1) it is expensive (both in direct cost and labor) to collect accurate data in the field regarding antimicrobial treatment efficacy, 2) virus exposure and the resulting clinical impact can mask the clinical efficacy of antimicrobial treatment, and 3) mass injection of a pen at a specific time point was superior to the other treatment regimens available in this study.

Contact Information: Christopher Rademacher, Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, email: [email protected], telephone: 515-294-8792

Key Findings:
• It is expensive (both in direct cost and labor) to collect accurate data in the field regarding antimicrobial treatment efficacy and may rival the cost of tightly controlled laboratory challenge studies.
• Virus exposure and the resulting clinical impact can mask the clinical efficacy of antimicrobial treatment. Controlling virus impacts has the potential to improve antimicrobial efficacy.
• Mass injection of a pen at a specific time point was superior to the other treatment regimens available in this study.