Clinical field trials with tilmicosin phosphate in feed for the control of naturally acquired pneumonia caused by Actinobacillus pleuropneumoniae and Pasteurella multocida in swine.

OBJECTIVE: To determine and evaluate the efficacy of the dose range of tilmicosin phosphate fed to pigs for control of pneumonia attributable to Actinobacillus pleuropneumoniae during episodes of clinical disease in commercial herds.
DESIGN: 12 trials were run in 9 geographic locations in herds with a history of pneumonia caused by A pleuropneumoniae. ANIMALS: Clinically normal male and female pigs of various body weights. PROCEDURE: Two doses of tilmicosin phosphate (200 and 400 micrograms/g) and a 0 dose were administered in the feed for 21 days. Variables for determining efficacy were daily independent composite clinical impression score, individual pig weight, mortality, percentage of pneumonic involvement, and frequency of isolation of bacterial pathogens.
RESULTS: Medicated pigs had significantly lower mortality attributed to pneumonia than did nonmedicated pigs. In trials with confirmed pneumonia caused by A pleuropneumoniae or Pasteurella multocida, weight gain, feed conversion, and clinical impression scores were significantly improved in the pigs receiving 200 or 400 micrograms/g of tilmicosin, compared with nonmedicated pigs.
CONCLUSIONS: The clinical field trials reported here confirm that tilmicosin in the feed at 200 micrograms/g is effective for control of swine pneumonia attributable to A pleuropneumoniae or P multocida. CLINICAL RELEVANCE: Under the moderate natural challenge conditions encountered, tilmicosin at 400 micrograms/g was not different from tilmicosin at 200 micrograms/g.