Administration of zilpaterol hydrochloride alters feedlot performance, carcass characteristics, muscle, and fat profiling in finishing Hanwoo steers

Forty Hanwoo steers weighing 759.3±50.3. kg were used to evaluate the effects of treatment with zilpaterol hydrochloride (ZH) in terms of feedlot performance, carcass characteristics, and fatty acid composition. We hypothesized that treatment of ZH increases meat amount in long-fed Hanwoo steers. Animals were blocked by BW, and assigned to one of two treatments within each block. Five animals were housed and fed in each of 8 pens. All animals were weighed before and after ZH treatment. Total BW gain over the 23-d period was adjusted to d 0 by covariant analysis. Steers receiving ZH (1.6. g/h/d) exhibited significantly increased weight gain (P<0.05) over CON steers. Performance analysis showed that ZH had significant effects on total weight gained average daily gain (ADG). There were also treatment effects (P<0.05) on dressing percentage, LM area, and yield grade. The total percentage of lean muscle was increased by the administration of ZH, and the percentage of fat was decreased by ZH treatment (P<0.05). The weights of tenderloin, striploin, chuck, round, shank, and brisket were significantly increased by ZH treatment compared to CON steers (P<0.05). Analyses of the physico-chemical characteristics of the longissimus muscle indicated that shear force, purge loss, and cooking loss were increased with ZH treatment (P<0.05). However, there were no treatment effects on marbling score and fatty acid compositions (P>0.05). We conclude that the administration of ZH increased LM area and primal yield grades, but had no change in the fatty acid profile.