Orally administered tylosin for the control of pneumonia in neonatal calves.

The effectiveness of orally administered tylosin tartrate for the control of naturally occurring pneumonia was determined in 287 neonatal calves. Tylosin tartrate was mixed with reconstituted milk replacer at the time of feeding. Daily doses of 1.0 g (0.5 g BID), 2.0 g (1.0 g BID) and 4.0 g (2.0 g BID) were evaluated for periods ranging from seven to 28 days. Tylosin at the optimum dose of 2.0 g daily reduced mortality to 12 out of 95 (12.6 per cent) compared to 38 out of 89 (42.7 per cent) in the non-medicated control calves. The 1.0 g daily dose did not reduce mortality. The number of calves with moderate to severe lung lesions was also reduced by treatment at 2.0 g daily to 13 out of 95 (13.7 per cent) compared to 45 out of 89 (50.6 per cent) in the control group. All dose levels had a similar effect in reducing the severity of clinical signs indicative of respiratory disease. Tylosin treatment at all dose levels reduced the number of Pasteurella multocida isolations from lung tissue to 15/146 (10.3 per cent) compared to 61/141 (43.3 per cent) for the controls. However, there were no differences between treated and controls in the number of P haemolytica isolations. The frequency of mycoplasma isolations from lung tissue were reduced significantly by tylosin treatment at the 4.0 g and 2.0 g dose levels to 36/93 (38.7 per cent) compared to 61/86 (70.9 per cent) for the control calves.