Protein level and β2-adrenergic agonist supplementation on growth performance and dietary energy of hairy lambs

Alfredo Estrada-Angulo; Beatriz Isabel Castro-Pérez; Jorge Luis Ramos-Méndez; Yesica Arteaga-Wences; Jesús D. Urías-Estrada; Alberto Barreras; Richard A. Zinn; Alejandro Plascencia

Alfredo Estrada-Angulo, PhD Autonomous University of Sinaloa, Culiacan 80260, Mexico
Beatriz Isabel Castro-Pérez Autonomous University of Sinaloa, Culiacan 80260, Mexico
Jorge Luis Ramos-Méndez Autonomous University of Sinaloa, Culiacan 80260, Mexico
Yesica Arteaga-Wences Autonomous University of Sinaloa, Culiacan 80260, Mexico
Jesús D. Urías-Estrada Autonomous University of Sinaloa, Culiacan 80260, Mexico
Alberto Barreras Autonomous University of Baja California, Mexicali 21100, Baja California, Mexico
Richard A. Zinn University of California, Davis, CA 95616
Alejandro Plascencia Autonomous University of Sinaloa, Culiacan 80260, Mexico http://orcid.org/0000-0003-2151-5372

Keywords: Zilpaterol hydrochloride, Feeding strategy, Feedlot lambs, Performance, Carcass.

Abstract

Zilpaterol hydrochloride (ZH) is a β2-adrenergic agonist used as a feed additive during fattening phase that increases growth performance and carcass in lambs by increasing tissue protein accretion. However, information about the effects of high protein level in diet on the responses to ZH in feedlot diets for lambs is unknown. For this reason, a study was conducted to evaluate the interaction of two dietary protein levels (15 and 18% CP, dry matter basis) and two dietary ZH levels (0 and 6 mg/kg of diet dry matter) on growth performance, dietary energy, and carcass dressing percentage of finishing lambs. For the above, 40 Pelibuey × Katahdin (37.8±2.2 kg) crossbred intact male lambs were used in a feeding trial which lasted 33 days. Lambs were grouping to 5-pen blocks (two lambs per pen, 5 replicas per treatment). Both diets contained similar energy concentration (~2.05 Mcal NE_m/kg). At the final of feeding trial, all lambs were slaughtered and dressing percentage was determined. No interactions were detected between protein level and ZH supplementation. Increasing crude protein level from 15 to 18% did not affect (P≥0.18) dry matter intake (DMI), average daily gain (ADG), gain to feed ratio (GF), and dietary net energy (NE). Inclusion of ZH in diets did not affect (P=0.17) DMI, but increased (P<0.01) ADG (16.2%), increasing GF and dietary NE (16 and 10.5%, respectively). Protein level did not affect (P≥0.78) carcass weight or carcass dressing percentage, while ZH supplementation increased both carcass weight (4.2%, P<0.01) and dressing percentage (2.59%, P=0.04) independent of protein level. The β2-adrenergic agonist zilpaterol hydrochloride is a tool to enhance growth performance and carcass in finishing lambs. The increase in protein level from 15 to 18% during the late phase of finishing (i.e., 30 d) did not improve growth performance or carcass weight in response to ZH supplementation.