This study analyzed the effects of an oral treatment with tiamulin (tiamulin hydrogen fumarate, "Denagard (R) 45 %" oral, Novartis Animal Health Inc., D) against various pathogens of the lung on a conventional pig farm. The trial included 150 pigs (nine weeks of age) randomly divided in a treatment (TIA) and a control (KONT) group with 75 pigs per group. All pigs in the pen of the treatment group (TIA) received 15 mg tiamulin (,,Denagard (R) 45 % oral", Novartis Tiergesundheit GmbH, D) per kg bodyweight per day by water over 14 days. Both groups were housed in the same room. 30 pigs from each group served as sampling animals from which bronchoalveolar lavage fluid (BALF) was collected and a clinical score was determined on study days (ST) 0, 14 and 21. Additionally a cough index was calculated for both groups on ST 1-3, 5, 7, 9, 11, 13-15, 17, 19 and 21. All animals were weighed individually on ST 0, 14 and 21. BALF was submitted for bacteriological examination and for detection of Mycoplasma (M.) hyopneumo- nine and M. hyorhinis employing culture and PCR. In group TIA the mean amount of Haemophilus (H.) parasuis (ST 0 to 14, 21), M. hyorhinis (ST 14 to 21) and M-haemolytic streptococci (ST 0 to 14) was significantly reduced. In group KONT the amount of H. parasuis was significantly reduced (ST 0 to 14, 21) as well. Actinobacillus pleuropneumoniae was only isolated from the BALF of six animals on ST 0. The mean amount of Bordetella bronchiseptica and Pasteurella multocida did not differ significantly between sampling days during the study. M-haemolytic streptococci were only isolated in very few cases. Clinical score, cough index, and weight gain differed significantly between study groups in favour of the treated animals. In this study, treating pigs with tiamulin led to a significant reduction of several pathogens of respiratory diseases which went along with a significantly improved clinical picture and a significantly higher daily weight gain in the treatment group when compared to the control group. Results of the study groups might have influenced each other by housing treated and untreated animals within one room.
