The effect of feed additive program in steam-flaked corn diets containing wet distiller's grains on performance and carcass merit in yearling feedlot steers

Abstract

Crossbred yearling steers (432, BW = 329 ± 10.5 kg) were used in an unbalanced randomized block design to examine the effect of feed additives on performance and carcass merit. Treatment factors were arranged as a 2 x 2 factorial and included ionophore and antibiotic [Rumensin/Tylan (R/T) or Cattlyst/Aureomycin (C/A)] and dietary S (constant or variable). High S diets were fed on random days to the variable (VAR) treatment. Low S diets were fed to the VAR treatment on remaining days and to the constant (CON) treatment all days. From d 0 through 35, the high S diet was achieved by using a high S granular supplement; however, since S concentration in wet distillers grains (WDG) is associated with distillers solubles (DS) added to WDG and H2SO4 added to the DS, the high S diet was achieved from d 36 through 159 by using a DS based liquid supplement with 2.35% S while the low S diet was achieved using a 0.99% S DS based liquid supplement. Cause of cattle death for study steers was verified by necropsy. No interaction between S and additive treatments existed for feedlot performance; therefore, only main effects are presented. Most of the sulfur comparisons from this study will be addressed in another manuscript. Feedlot performance and carcass merit were similar for feed additive treatments. The S by feed additive interaction was significant (P < 0.05) for dressing percentage indicating that S treatment had no effect on dressing percentage if R/T was fed but when steers were fed C/A, dressing percentage was reduced by 0.72% (P < 0.02) if VAR diets were fed. The results of this study indicate that performance and carcass characteristics for cattle fed Cattlyst and Aureomycin are similar to performance and carcass characteristics for cattle fed Rumensin and Tylan.