Effects of zilpaterol hydrochloride on feedlot performance and carcass characteristics of hair-breed ram lambs
Twenty-one Dorper × Pelibuey croosbred ram lambs (39.01 ± 1.09 kg; 4 mo of age) were individually housed in pens equipped with shade, feed troughs and automatic waterer. Ram lambs were adapted to pens and basal diet, during a 20-d period. One week before initiation of the experimental phase, lambs were individually weighed, stratified by BW and randomly assigned to treatments under a completely randomized design to evaluate effects of zilpaterol hydrochloride (ZH) levels (ZH; 0, 10 and 20 mg/lamb daily; in order to ensure a total intake of ZH, 133.33 g was mixed with 19.1 kg of wheat meal, and 30 g/lamb daily of mixture was offered to lambs before the morning feeding) on feedlot performance, carcass characteristics, and wholesale cut yield of ram lambs. After a 30 d feeding period, all lambs were harvested. Entire feeding period, ZH increased (P ≤ 0.05) ADG and tended to increase (P = 0.076) feed intake. G:F was not affected (P = 0.38). In addition, ZH improved hot carcass weight, cold carcass weight, conformation (ranked 1: bad and 10: excellent), and dressing percent (P ≤ 0.05). ZH don´t affected (P ≥ 0.05) KPH fat, but tended (P = 0.08) to improved LM area (cm2). ZH at 10 mg/lamb dose increased (P = 0.005) carcass length (cm), but ZH at 20 mg/lamb dose showed the highest leg perimeter (P ≤ 0.01). ZH affected (P ≤ 0.05) LM pH at 24 h postmortem (P ≤ 0.05). All non-carcass components were not affected (P ≥ 0.05) by ZH doses. Leg yield (P = 0.01) and plain loin (P = 0.04) decreased with ZH and yields of other wholesale cuts were not affected (P ≥ 0.1). Inclusion of ZH improve some variables of feedlot performance and carcass characteristics of economic importance such as ADG, feed intake and LM area, carcass leg and leg perimeter.
Keywords: β-adrenergic agonist, feedlot sheep, growth rate, carcass characteristics