The effect of tylosin supplementation and tylosin alternative control treatments on fecal microbial populations, performance, and liver abscess prevalence in feedlot cattle

An abstract of a study by Weissend et al evaluating the effect of tylosin and two alternative treatments on fecal microbial populations, feedlot performance, and the prevalence of liver abscesses in feedlot cattle is presented. Commercial steers and heifers (n = 5,481 hd) from similar sources were placed on feed at a commercial feedyard in Texas. Ten 4-pen blocks (40 pens) were assembled beginning in Mar 2016. At placement, cattle were randomly assigned to one of four treatment groups: finishing ration with tylosin (90 mg/hd/d) fed until harvest, finishing ration without tylosin or other treatments, finishing ration without tylosin, but with an essential oil fed until harvest, or finishing ration without tylosin but with a yeast fermentation by-product (18 g/hd/d) fed until harvest. A composite fecal sample was obtained from each pen floor within four weeks of placement and again two to four d prior to harvest in order to evaluate fecal microbial populations and obtain isolates of Salmonella enterica, Enterococcus, and non-type-specific Escherichia coli for further characterization. At the conclusion of the finishing period, cattle were harvested at a commercial processing facility. Livers were evaluated for abscess prevalence and severity scoring at harvest.