Targeted durations of tylosin phosphate on incidence and severity of liver abscesses in feedlot cattle*

Objective

Our objective was to assess the effects of feeding tylosin phosphate at 60 mg∙steer⁻¹∙d⁻¹ for the first 30 or 60 d of the finishing phase on the incidence and severity of liver abscesses, performance, and carcass characteristics in feedlot steers.

Materials and Methods

Steers (n = 462) were randomly assigned to 1 of 3 treatments: no tylosin phosphate (control) or tylosin phosphate, administered in the feed as a type B medicated premix supplement, to provide 60 mg∙steer⁻¹∙d⁻¹ for the first 30 d (T-30) or 60 d (T-60) of the finishing phase (steers were fed the control diet for the remaining days of the finishing phase). Steers were housed in pens with 7 steers per pen and 22 pens per treatment. Cattle BW were recorded at 30-d intervals, and final BW was recorded on d 161 on feed. Steers were processed at a commercial abattoir, and incidence and severity of liver abscesses and carcass characteristics were recorded.

Results and Discussion

Incidence of abscessed livers was not affected by targeted durations of tylosin phosphate administration. However, there was a trend for severe abscesses to happen less in T-30 and T-60 than in the control, possibly because of inclusion of tylosin phosphate during the diet transition phase when cattle are likely to experience ruminal acidosis. Steers that received tylosin phosphate had greater BW on d 30 or 60 compared with the control. Steer performance and carcass characteristics were not affected by treatments.

Implications and Applications

Administration of tylosin phosphate at 60 mg per animal daily for the first 30 or 60 d of the finishing phase had no effect on the incidence of abscessed livers, although there was a trend for the reduction in severe abscesses in feedlot steers.