Removing tylosin phosphate from finishing diets with increasing roughage concentrations affects growth performance, carcass characteristics, and prevalence of liver abscesses of finishing steers*

Objectives

This study compared standard finishing diets with or without tylosin phosphate at an industry standard roughage concentration, as well as titrated roughage concentrations in finishing diets containing no tylosin.

Materials and Methods

Beef steers (initial BW = 387 ± 14.2 kg; n = 3,340) were used in a randomized complete block design with 12 pens/treatment and 65 or 70 steers per pen. Dietary treatments were (1) 7.0% corn stalks with tylosin (7TYL), (2) 7.0% corn stalks without tylosin (7NT), (3) 13.0% corn stalks without tylosin (13NT), or (4) 19.0% corn stalks without tylosin (19NT). Corn stalks replaced steam-flaked corn on a DM basis.

Results and Discussion

Increased corn stalks linearly increased DMI. Increased corn stalks linearly reduced final BW and ADG, and resulted in poorer G:F. Hot carcass weight was similar between 7TYL and 7NT; however, hot carcass weight (HCW) linearly decreased as corn stalk inclusion increased. Tylosin inclusion resulted in a 32% reduction in liver abscess prevalence (from 19% to 13%). Liver abscess prevalence decreased linearly with increased corn stalks; tylosin use reduced adhered livers, whereas increased corn stalks did not.

Implications and Applications

Replacing steamflaked corn with 13% or 19% inclusion of corn stalks in diets without tylosin phosphate could reduce liver abscess prevalence, but increased roughage may not decrease the severity of the liver abscesses. Importantly, decreased dietary energy density led to increased DMI and reduced HCW in cattle fed to the same days on feed.