INFLUENCE OF DURATION OF ZILPATEROL SUPPLEMENTATION ON CARCASS CHARACTERISTICS AND MEAT QUALITY OF FINISHED LAMBS

Supplementing zilpaterol hidrochloride (ZH) in lambs improves growth performance and carcass yield. Typically, ZH supplementation is initiated 32 d before slaughter, consisting of a 30-d feeding period followed by a 2-d withdrawal period. Previous studies have shown that ZH tend to be more effective when administered over short periods near the end of feedlot phase. The objective of this study was to evaluate the effect of supplementation duration (control, 10, 20 or 30 d) of zilpaterol hydrochloride (ZH) on carcass characteristics, cutability, and meat quality in forty 4-month-old Dorper x Kathadin male lambs (body weight = 34.6 ± 2.4 kg; 10 lambs per treatment). Omental fat deposition and shoulder percentage decreased (linear effect, P <0.05), whereas carcass weight and the proportions of loin and leg increased (linear effect, P<0.05) with increasing duration of ZH supplementation. However, no treatment effects were observed (P > 0.10) on the proportion of primary cuts or on post-mortem pH of the L. thoracis muscle (0.05). Meat shear force increased (linear effect, P <0.05) as the duration of ZH supplementation increased. ZH supplementation was economically profitable, regardless of the number of days it was administered, with greater efficiency observed as the supplementation period increased.